tag:theconversation.com,2011:/us/topics/erosion-1446/articlesErosion – The Conversation2024-03-07T22:03:41Ztag:theconversation.com,2011:article/2249022024-03-07T22:03:41Z2024-03-07T22:03:41ZFlood risk mapping is a public good, so why the public resistance in Canada? Lessons from Nova Scotia<p>Flood risk maps are an essential public good. Indeed, many countries like the <a href="https://flood-map-for-planning.service.gov.uk/">United Kingdom already offer flood risk mapping</a>.</p>
<p>Canada committed to a public flood risk mapping portal in the <a href="https://www.budget.canada.ca/2023/report-rapport/chap4-en.html#Raising%20Awareness%20of%20Flood%20Risks">2023 budget</a>. However, despite the <a href="https://www.theweathernetwork.com/en/news/climate/impacts/climate-water-is-the-new-fire">increasing frequency and impact of large, catastrophic floods</a>, we still have a sparse patchwork of flood risk maps at municipal and provincial scale. </p>
<p>What <a href="https://floodsmartcanada.ca/floodplain-maps/">flood mapping that does exist</a> is hard to find, of uncertain quality and currency, and often <a href="https://globalnews.ca/news/5206284/bad-flood-map-canada/">difficult for non-experts to understand and apply</a>. </p>
<p>The unacknowledged reason why there is a lack of flood risk mapping in Canada is because such maps generally face public resistance. Indeed, it is not uncommon in Canada to see flood or wetland mapping <a href="https://montreal.ctvnews.ca/quebec-withdraws-30-municipalities-from-contested-flood-zone-maps-1.4509236">withdrawn or modified</a> because of public pressure. </p>
<p>I led two survey-based studies recently with former graduate student Samantha Howard and post-doctoral fellow Brooke McWherter to understand how people in flood-prone areas of Nova Scotia perceive publicly available flood maps. We found wide agreement about the benefits of such maps — until we asked about the <a href="https://www.intactcentreclimateadaptation.ca/treading-water-impact-of-catastrophic-flooding-on-canadas-housing-market/">impact on real estate value</a>. </p>
<h2>The case of Nova Scotia</h2>
<p>Nova Scotia faces some of the <a href="https://changingclimate.ca/CCCR2019/chapter/8-0/">highest sea level rise in Canada</a> under current climate change projections. Yet last week, the Nova Scotia government <a href="https://www.cbc.ca/news/canada/nova-scotia/coastal-protection-act-environment-tim-halman-climate-change-1.7125745">decided not to proceed with the long-awaited Coastal Protection Act (CPA)</a>, which had been passed with all-party assent in 2019. </p>
<p>Among other things, the act would have regulated how close people could build to the ocean based on assessments of sea level, storm projections and information about the elevation and erosion risk of each section of coast. This would have protected people and infrastructure, as well as sensitive coastal ecosystems, and left space for ocean dynamics. </p>
<p>In lieu of the act, the Nova Scotia government released a <a href="https://novascotia.ca/coastal-climate-change/">new website</a> featuring resources to help individual coastal property owners make decisions about their bit of coastline, <a href="https://www.cbc.ca/news/canada/nova-scotia/municipalities-nova-scotia-coastal-protection-act-1.7021006">leaving dozens of rural coastal municipalities</a> in the lurch. One of those resources was a new <a href="https://nsgi.novascotia.ca/chm">coastal hazard map</a>. </p>
<p>The lengthy disclaimer you need to agree to before you can access the map immediately erodes its trustworthiness. Moreover, while people may trust any good news they see in its data, they may still be at risk due to the tool’s many data and design flaws. To supplement this tool, Nova Scotia has <a href="https://globalnews.ca/news/10317417/new-coastal-protection-plan-nova-scotia/">committed to finishing detailed flood line mapping by 2027</a>. </p>
<p>It is too soon to know how people are responding to this tool, but we know it does not take a lot of unhappy constituents to make a government nervous, especially if those constituents hold financial or political power. <a href="https://www.cbc.ca/news/canada/nova-scotia/coastal-protection-act-tim-halman-environment-climate-change-1.6959599">The public engagement associated with the CPA was, after all, overwhelmingly in support of proclaiming and regulating under the act</a>. Yet here we are. </p>
<h2>Drivers of resistance</h2>
<p>The first survey we ran in 2021 — through an online link sent via Canada Post to all residents in two towns in Southwestern Nova Scotia — showed <a href="https://doi.org/10.1111/cag.12836">one in six people felt flood risk mapping presented too big a risk for real estate value</a>. Our second survey of about 1100 house residents around the Minas Basin, Nova Scotia, in 2022 found that <a href="http://hdl.handle.net/10222/83004">one in three residents expressed concern about real estate value</a>. Both studies had a margin of error of plus or minus 6 per cent at a 95 per cent confidence level.</p>
<p>The first survey had a smaller response rate but represented the population demographics better. The second was biased toward older respondents and those with higher incomes. </p>
<p>Moving back to our original question — why doesn’t everyone see flood risk mapping as a public good?</p>
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<a href="https://theconversation.com/2023s-billion-dollar-disasters-list-shattered-the-us-record-with-28-big-weather-and-climate-disasters-amid-earths-hottest-year-on-record-220634">2023's billion-dollar disasters list shattered the US record with 28 big weather and climate disasters amid Earth's hottest year on record</a>
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<p>We used slightly different questions in the two studies to understand the drivers of resistance to flood risk mapping based on perceived impact on real estate value. What emerged speaks to the challenge of inspiring long-term and collective thinking about climate change. </p>
<p>Firstly, being focused on oneself rather than others was a reliable predictor of resistance in both studies. </p>
<p>Resistance in the first study was associated with agreeing to the following statements: “I am not able to cope with the land changes required to deal with significant increases in flood risk at this point in my life,” and “flood management decisions I make do not have implications for others.” The latter is demonstrably untrue: shoreline armouring, for instance, can have negative effects for neighbours. In the second study, being focused on others and having descendants led to less resistance. </p>
<p>Self-orientation was a strong underlying driver of resistance. It reduced a person’s likelihood of focusing on others, the future or the biosphere. People already make decisions to suit their own situation, just as the Nova Scotia government is now <a href="https://www.halifaxexaminer.ca/morning-file/the-houston-government-thinks-we-can-use-an-app-to-ward-off-storm-damage-and-sea-level-rise-individually-we-cant/#N1">encouraging coastal landowners to do</a>. Yet in these kinds of scenarios, collective and ecological interests are forgotten.</p>
<p>Secondly, the more vulnerable a person felt to flood risk, the more likely they were to oppose maps that would allow others to see their flood risk. This variable was only a strong signal of resistance in the second study when we used a combination of flood likelihood and vulnerability to measure it. This might also explain why resistance was twice as high in the 2022 survey than the one in 2021. It could be a regional difference based on actual differences in risk, or differences in survey method and thus respondent population, but it could also reflect increasing flood frequency and severity.</p>
<p>The second survey was still in the field when <a href="https://www.cbc.ca/news/canada/nova-scotia/weather-snoddon-fiona-recap-1.6976249">Hurricane Fiona</a> hit Atlantic Canada. This timing suggests that instead of becoming more open to climate adaptation information like flood maps as flooding events occur, we might become less open as we seek to protect the value of our biggest investments: our homes. </p>
<h2>Moving forward</h2>
<p>A clue to the path ahead may be found in our first study, where <a href="https://doi.org/10.1111/cag.12836">those who had previously seen a flood map for their region</a> were slightly less likely to be resistant to public flood risk maps. This might indicate that such resistance is mostly borne of fear of the unknown. </p>
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Read more:
<a href="https://theconversation.com/wetlands-are-superheroes-expert-sets-out-how-they-protect-people-and-places-221995">Wetlands are superheroes: expert sets out how they protect people and places</a>
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<p>We urgently need high quality, public flood risk maps that the government stands by (including with planning regulations). Then we can focus on rethinking what it means to live a good coastal life in the face of climate change, and how we collectively support those who may face decreases in home or land value.</p><img src="https://counter.theconversation.com/content/224902/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kate Sherren or her trainees received funding for this work from the Social Sciences and Humanities Research Council, the Natural Sciences and Engineering Research Council, and the Nova Scotia Government. </span></em></p>Public concerns for real estate value, and a focus on the self, make flood risk maps unpopular. However, these concerns should not dissuade governments from providing resources we can all trust.Kate Sherren, Professor, School for Resource and Environmental Studies, Dalhousie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2248692024-03-05T15:02:19Z2024-03-05T15:02:19ZArctic rivers face big changes with a warming climate, permafrost thaw and an accelerating water cycle − the effects will have global consequences<figure><img src="https://images.theconversation.com/files/579392/original/file-20240303-24-mmw6cz.jpg?ixlib=rb-1.1.0&rect=0%2C1333%2C9000%2C6157&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Water from the Mackenzie River, seen from a satellite, carries silt and nutrients from land to the Arctic Ocean.</span> <span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/90703/mackenzie-meets-beaufort">Jesse Allen/NASA Earth Observatory</a></span></figcaption></figure><p>As the Arctic warms, its mighty rivers are changing in ways that could have vast consequences – not only for the Arctic region but for the world.</p>
<p>Rivers represent the land branch of the earth’s hydrological cycle. As rain and snow fall, rivers transport freshwater runoff along with dissolved organic and particulate materials, including carbon, to coastal areas. With the Arctic now warming nearly <a href="https://theconversation.com/arctic-is-warming-nearly-four-times-faster-than-the-rest-of-the-world-new-research-188474">four times faster</a> than the rest of the world, the region <a href="https://doi.org/10.1175/2010JCLI3421.1">is seeing more precipitation</a> and the permafrost is thawing, leading to stronger river flows.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows major rivers and their water sheds, primarily in Russia, Alaska and Canada." src="https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=596&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=596&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=596&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=749&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=749&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=749&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Major river basins of the Arctic region.</span>
<span class="attribution"><a class="source" href="https://www.pmel.noaa.gov/arctic-zone/detect/land-river.shtml">NOAA Arctic Report Card</a></span>
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<p>We’re climate scientists who study how warming is influencing the water cycle and ecosystems. <a href="https://doi.org/10.5194/tc-18-1033-2024">In a new study</a> using historical data and sophisticated computer models of Earth’s climate and hydrology, we explored how climate change is altering Arctic rivers. </p>
<p>We found that thawing permafrost and intensifying storms will change how water moves into and through Arctic rivers. These changes will affect coastal regions, the Arctic Ocean and, potentially, the North Atlantic, as well as the climate.</p>
<h2>Thawing permafrost: Big changes in Arctic soils</h2>
<p>Permafrost thaw is one of the most consequential changes that the Arctic is experiencing as temperatures rise. </p>
<p>Permafrost is soil that has been <a href="https://climate.mit.edu/explainers/permafrost">frozen for at least two years</a> and often for millennia. It covers approximately 8.8 million square miles (about 22.8 million square kilometers) in Earth’s Northern Hemisphere, but that area is shrinking as the permafrost thaws.</p>
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<a href="https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two people stand on a cliff with permafrost evident." src="https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Erosion reveals ice-rich permafrost near Teshekpuk Lake, Alaska.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/usgeologicalsurvey/12116729705">Brandt Meixell/USGS</a></span>
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<a href="https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows where permafrost is found, both in ground and below the ocean." src="https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=534&fit=crop&dpr=1 754w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=534&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=534&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Known permafrost zones in the Northern Hemisphere.</span>
<span class="attribution"><a class="source" href="https://www.grida.no/resources/13519">GRID-Arendal/Nunataryuk</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Historically, most water going into Arctic rivers flows atop frozen permafrost soils in spring. Scientists call this “overland runoff.” </p>
<p>However, our results suggest that as warming continues, an increasing fraction of annual river flow will come from under the surface, through thawed soils in the degrading permafrost. As the overall flow increases with more precipitation, as much as 30% more of it could be moving underground by the end of this century as subsurface pathways expand.</p>
<p>When water flows through soil, it picks up different chemicals and metals. As a result, water coming into rivers will likely have a different chemical character. For example, it may carry more nutrients and dissolved carbon that can affect coastal zones and the global climate. The fate of that mobilized carbon is an active area of study.</p>
<p>More carbon in river water could end up “outgassed” upon reaching placid coastal waters, increasing the amount of carbon dioxide released into the atmosphere, which further drives <a href="https://doi.org/10.1038/nature14338">climate warming</a>. The thaw is also revealing other nasty surprises, such as the <a href="https://www.usatoday.com/story/news/politics/2023/11/18/arctic-permafrost-thawing-deadly-pathogens/71581668007/">emergence of long-frozen viruses</a>. </p>
<h2>More rain and snow, more runoff</h2>
<p>The Arctic’s water cycle is also ramping up as temperatures rise, meaning more precipitation, evaporation, plant transpiration and river discharge. This is primarily due to a warmer atmosphere’s inherent ability to hold more moisture. It’s the same reason that <a href="https://theconversation.com/why-a-warming-climate-can-bring-bigger-snowstorms-176201">bigger snowstorms are occurring</a> as the climate warms. </p>
<p>Our study found that the bulk of the additional precipitation will occur across far northern parts of the Arctic basin. As sea ice disappears in a warming climate, computer models agree that a more open Arctic Ocean will feed more water to the atmosphere, where it will be transported to adjacent land areas to fall as precipitation. </p>
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<span class="caption">Changes projected this century in annual rainfall and snowfall simulated by the computer model used in the study. Red areas represent increases.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.5194/tc-18-1033-2024">Rawlins and Karmalkar, 2024</a></span>
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<p>More snow in northern Alaska, Siberia and Canada will lead to more water flowing in rivers, potentially up to 25% more under a high-warming scenario based on our research. There is more carbon in the soil in northern parts of the Arctic compared with the south. With permafrost thaw, those regions will also see more water coming into rivers from below the surface, where additional soil carbon can leach into the water and become dissolved organic carbon.</p>
<p>More <a href="https://doi.org/10.1088/1748-9326/aaa1fe">old carbon is already showing up</a> in samples gathered from Arctic rivers, attributed to permafrost thaw. Carbon dating shows that some of this carbon has been frozen for thousands of years. </p>
<h2>Impacts will cascade through Arctic ecosystems</h2>
<p>So, what does the future hold? </p>
<p>One of the most notable changes expected involves the transport of fresh water and associated materials, such as dissolved organic carbon and heat energy, to Arctic coastal zones. </p>
<figure class="align-center ">
<img alt="A scientist in a rain jacket and cap holds up a water sample in a jar." src="https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">James McClelland of the Beaufort Lagoon Ecosystems Long Term Ecological Research program examines a water sample from a stream near Utqiagvik on Alaska’s North Slope. The brown tint is dissolved organic matter.</span>
<span class="attribution"><span class="source">Michael A. Rawlins</span></span>
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<p><a href="https://ble.lternet.edu/">Coastal lagoons</a> may become fresher. This change would affect organisms up and down the food chain, though <a href="https://doi.org/10.3389/fmars.2022.738363">our current understanding</a> of the potential affects of changes in fresh water and dissolved organic carbon is still murky.</p>
<p>River water will also be warmer as the climate heats up and has the potential to melt coastal sea ice earlier in the season. Scientists <a href="https://theconversation.com/arctic-report-card-2023-from-wildfires-to-melting-sea-ice-the-warmest-summer-on-record-had-cascading-impacts-across-the-arctic-218872">observed this in spring 2023</a>, when unusually warm water in Canada’s Mackenzie River carried heat to the Beaufort Sea, contributing to early coastal sea ice melting.</p>
<figure class="align-center ">
<img alt="A satellite view of the Arctic coast showing a river and sea ice breaking up." src="https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fresh water flowing from rivers such as Canada’s Mackenzie River, at the bottom center of the satellite image, into the Beaufort Sea can break up sea ice early.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/83271/river-discharge-alters-arctic-sea-ice">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<p>Finally, more river water reaching the coast has the potential to freshen the Arctic Ocean, particularly along northern Eurasia, where big Russian rivers export massive amounts of fresh water each year. </p>
<p>There are concerns that <a href="https://arctic.noaa.gov/report-card/report-card-2021/river-discharge/">rising river flows in that region</a> are influencing the Atlantic Meridional Overturning Circulation, the currents that circulate heat from the tropics, up along the U.S. East Coast and toward Europe. Evidence is mounting that these currents <a href="https://theconversation.com/the-atlantic-oceans-major-current-system-is-slowing-down-but-a-21st-century-collapse-is-unlikely-214647">have been slowing in recent years</a> as more fresh water enters the North Atlantic. If the circulation shuts down, it would <a href="https://theconversation.com/atlantic-ocean-is-headed-for-a-tipping-point-once-melting-glaciers-shut-down-the-gulf-stream-we-would-see-extreme-climate-change-within-decades-study-shows-222834">significantly affect temperatures</a> across North America and Europe.</p>
<p>At the coast, changing river flows will also affect the plants, animals and Indigenous populations that call the region home. For them and for the global climate, our study’s findings highlight the need to closely watch how the Arctic is being transformed and take steps to mitigate the effects.</p><img src="https://counter.theconversation.com/content/224869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael A. Rawlins receives funding from The Department of Energy, the National Aeronautics and Space Administration and the U.S. National Science Foundation. </span></em></p><p class="fine-print"><em><span>Ambarish Karmalkar receives funding from the Department of Energy and the United States Geological Survey. </span></em></p>A new study shows how thawing permafrost and intensifying storms will change how water moves into and through Arctic rivers.Michael A. Rawlins, Associate Director, Climate System Research Center and Associate Professor of Climatology, UMass AmherstAmbarish Karmalkar, Assistant Professor of Geosciences, University of Rhode IslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2223932024-02-06T05:02:52Z2024-02-06T05:02:52ZClimate change will strike Australia’s precious World Heritage sites – and Indigenous knowledge is a key defence<figure><img src="https://images.theconversation.com/files/573359/original/file-20240205-25-njg9qp.jpg?ixlib=rb-1.1.0&rect=64%2C6%2C4217%2C2837&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Cezary Wojtkowski, Shutterstock</span></span></figcaption></figure><p>From Kakadu to Uluru and the Great Barrier Reef, to Sydney Opera House and the convict sites, <a href="https://www.dcceew.gov.au/parks-heritage/heritage/places/world-heritage-list">Australia’s list</a> of World Heritage places is incredibly diverse. Each site represents the culture, nature and history of this land, in its own way. </p>
<p>But climate change threatens these sites. Many heritage values are already being eroded. On-ground managers of these and other protected places need practical guidance on how to understand these impacts and respond effectively. </p>
<p>We developed a <a href="https://www.dcceew.gov.au/parks-heritage/heritage/publications/climate-change-toolkit-world-properties">climate change “toolkit” for World Heritage properties</a> with site managers and Traditional Owners. To our knowledge, it is the first time such guidance has been co-developed and tested with World Heritage property managers and Indigenous experts in this country.</p>
<p>Bringing climate science and Indigenous knowledge systems together promises to produce better results for heritage protection as the climate changes. And there is no time to waste. We must act fast to address these threats to Australia’s unique and special places of global significance, so their World Heritage values can be enjoyed for generations to come.</p>
<h2>Mounting climate threats to heritage</h2>
<p><a href="https://doi.org/10.1016/j.biocon.2024.110459">Our new research</a> explored climate impacts at three very different sites: </p>
<ol>
<li><a href="https://whc.unesco.org/en/list/147/">Kakadu National Park</a>, Northern Territory</li>
<li><a href="https://whc.unesco.org/en/list/1306">Australian Convict Sites</a>, scattered around the country</li>
<li><a href="https://whc.unesco.org/en/list/167/">Willandra Lakes Region</a>, southwest New South Wales.</li>
</ol>
<p>The vast tropical <a href="https://whc.unesco.org/en/list/147/">Kakadu National Park</a> is one of four Australian properties listed for both outstanding cultural and natural values. Cave paintings, rock carvings and archaeological sites date back tens of thousands of years. Tidal flats, floodplains, lowlands and plateaus provide habitat for many rare or endemic plants and animals.</p>
<p>But Kakadu is vulnerable to rising sea levels, leading to coastal erosion and saltwater entering wetlands. The region is also experiencing more extreme temperatures and heatwaves, changing fire regimes, more intense cyclones, and increasingly intense extreme rainfall events. </p>
<p>The <a href="https://whc.unesco.org/en/list/1306/">Convict Sites</a> consist of 11 properties around Australia. Fremantle Prison lies 5,500km west of Arthur’s Vale Historic Area in the east. The Old Great North Road in the north is 1,500km from the Port Arthur Historic Site in the south.</p>
<p>Many convict sites are on coasts and islands where wave action and sea level rise are increasingly damaging structures, landscapes and cultural materials. Convict sites are also vulnerable to storms and bushfires because the buildings are so old. </p>
<p>The arid <a href="https://whc.unesco.org/en/list/167/">Willandra Lakes Region</a> contains fossil remains of a series of lakes and sand formations, along with archaeological evidence of human occupation dating back 45,000–60,000 years.</p>
<p>Hot and dry conditions are causing erosion of topsoil, increasingly exposing Aboriginal cultural heritage.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Outback landscape with delicate structures at Red Top lookout, Willandra Lakes, along the large lunette formed by wind and water erosion along a dried up lake" src="https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573669/original/file-20240206-19-5b8ppw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Climate change is exacerbating erosion at the Willandra Lakes World Heritage site.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/outback-landscape-delicate-structures-red-top-794485033">Leah-Anne Thompson, Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-must-be-a-catalyst-for-reform-of-the-world-heritage-system-191798">Climate change must be a catalyst for reform of the World Heritage system</a>
</strong>
</em>
</p>
<hr>
<h2>Tapping into deep knowledge</h2>
<p>We worked closely with these sites to develop and test our new toolkit.</p>
<p>An Indigenous Reference Group of Traditional Owners from a number of World Heritage sites in Australia contributed their expert knowledge. This includes practical guidance such as how to engage with and enable Indigenous leadership so Traditional Owners can participate in or lead climate vulnerability assessment and adaptation planning. The toolkit also describes using the right knowledge for the right Country (showing respect for traditional knowledge) and establishing agreements to ensure Indigenous cultural and intellectual property rights <a href="https://www.un.org/development/desa/indigenouspeoples/publications/2016/10/free-prior-and-informed-consent-an-indigenous-peoples-right-and-a-good-practice-for-local-communities-fao/">are protected</a>.</p>
<p>Effectively addressing climate impacts on World Heritage values requires the deep knowledge, values and worldviews of <a href="https://lcipp.unfccc.int/">Indigenous Peoples and local communities</a>. This includes practices such as cultural burning to reduce the risk of intense bushfire, or cultural knowledge of long-term changes in water cycles. Tapping into this deep understanding of <a href="https://doi.org/10.1038/s41893-023-01153-1">connections between nature and culture</a> can help support the management of spiritual, living landscapes. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1751832543866044903"}"></div></p>
<h2>Adapting to climate change</h2>
<p>World Heritage site managers can take a broad range of practical actions to adapt to climate change. </p>
<p>These actions, such as firefighting or invasive species control, may not be new. They just need to be undertaken more often or intensely. </p>
<p>Other variations on existing actions may include greater emphasis on physical separation between flammable vegetation and assets such as larger firebreaks, or responding to new invasive species, possibly including shifting ranges of invasive native species. </p>
<p>Some new management actions will be required, such as flood protection, relocating assets and new technological interventions. In cases where climate change is likely to lead to changes in the values of a site, there may be a need to reevaluate management objectives and strategies (such as accommodating new groups of organisms or “ecological communities”, letting some populations decline, and managed retreat of shorelines). </p>
<p>There may also be a need to consider vulnerability at different scales, sometimes across larger areas. In some cases, managers may aim to retain certain values across a wider landscape while accepting local change.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of Darlington, a convict site on Maria Island, Tasmania, take from some distance away to show all of the buildings together, with trees in the foreground and background" src="https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573684/original/file-20240206-17-l01akv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Darlington, on Maria Island, Tasmania, is one of 11 properties grouped together under the Australian Convict Sites World Heritage listing.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/darlington-historic-settlement-on-maria-island-247616818">David Lade, Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-adaptation-projects-sometimes-exacerbate-the-problems-they-try-to-solve-a-new-tool-hopes-to-correct-that-213969">Climate adaptation projects sometimes exacerbate the problems they try to solve – a new tool hopes to correct that</a>
</strong>
</em>
</p>
<hr>
<h2>Looking ahead</h2>
<p>Managers, stakeholders and rights-holders of World Heritage sites and other protected places, such as <a href="https://www.dcceew.gov.au/water/wetlands/australian-wetlands-database/australian-ramsar-wetlands">Ramsar wetlands</a> and <a href="https://www.dcceew.gov.au/sites/default/files/documents/nrsmpa-protect.pdf">marine protected areas</a>, can now use the toolkit to plan for current and future climate threats. They can focus on the parts most useful to them, depending on their capacity and needs. Ultimately, this resource will help protect Australia’s cultural and natural heritage.</p>
<hr>
<p><em>The following people were members of the Indigenous Reference Group and are coauthors of our research paper: Bianca McNeair, Lance Syme, Chrissy Grant, Nicholas Pedrocchi, Patricia Oakley, Amy Stevens, Denis Rose, Erin Rose, Jade Gould, John Locke and Lynda Maybanks.</em></p><img src="https://counter.theconversation.com/content/222393/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jess Melbourne-Thomas received funding for this work from the Australian Commonwealth Department of Climate Change, Energy, the Environment and Water. </span></em></p><p class="fine-print"><em><span>Brenda Lin received funding for this work from the Australian Commonwealth Department of Climate Change, Energy, the Environment and Water.</span></em></p><p class="fine-print"><em><span>Lance Syme is Principal Archaeologist at Kayandel Archaeological Services, providing cultural heritage and archaeological consulting services throughout New South Wales. He is now working part-time for the International Indigenous Peoples Forum on World Heritage. Funding for the work described in this article came from the Australian Commonwealth Department of Climate Change, Energy, the Environment and Water. </span></em></p><p class="fine-print"><em><span>Mandy Hopkins received funding for this work from the Australian Commonwealth Department of Climate Change, Energy, the Environment and Water. This led to further support for vulnerability assessments from Budj Bim world heritage property management. </span></em></p>Researchers, managers and Traditional Owners are joining forces to understand and combat climate threats to Australia’s many unique World Heritage sites.Jess Melbourne-Thomas, Transdisciplinary Researcher & Knowledge Broker, CSIROBrenda Lin, Principal research scientist, CSIROLance Syme, Secretariat at the International Indigenous Peoples Forum on World Heritage, Indigenous KnowledgeMandy Hopkins, Adjunct industry fellow, University of Southern QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2156312023-11-16T14:47:59Z2023-11-16T14:47:59ZClimate change and farming: economists warn more needs to be done to adapt in sub-Saharan Africa<p>Sub-Saharan African countries strongly rely on the agricultural and forestry sectors. Agriculture contributes up to <a href="https://data.worldbank.org/indicator/NV.AGR.TOTL.ZS?locations=ZG">60%</a> of some countries’ gross domestic product. But the sector is highly vulnerable to climate change because it relies heavily on climatic factors. This vulnerability is particularly marked in the region because of its slow rate of technological advancement.</p>
<p>As agricultural economists we carried out a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0959652623016451">review</a> of the literature on the climate change challenge for agriculture in sub-Saharan Africa. We explored the distribution of various climatic factors (like rainfall, temperature and extreme weather events) across the region, and their impact on agriculture. We also investigated what rural farmers were doing to respond to climate change. </p>
<p>We found that the implications of climate change for agricultural and economic development are diverse across the region. It is difficult to predict exactly how climate change will affect agriculture and economic development. </p>
<p>But is is clear that sub-Saharan African countries like Nigeria, South Africa, Botswana, and Kenya are <a href="https://www.sciencedirect.com/science/article/abs/pii/S0959652623016451">extremely vulnerable</a> to <a href="https://www.afdb.org/en/cop25/climate-change-africa">climate change</a>. </p>
<p>Farmers are not using effective adaptation strategies. These include planting drought tolerant crop varieties, and conserving water and soil. Limited resources and infrastructure have held them back. Mitigation programmes such as carbon pricing, water management, recycling, afforestation and reforestation have had limited impact. Poor climate change awareness, unstable government policies and political instability have hindered the programmes.</p>
<p>The impact of climate change on vulnerable households will be extreme if adequate measures are not taken in time. Research suggests that countries such as Togo, Nigeria, Congo and Mali will record more agricultural <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/AR5_SYR_FINAL_SPM.pdf#page=13">losses</a> without adaptation. Governments, international organisations, local communities and other stakeholders need to develop strategies to address the diverse needs of rural farmers in sub-Saharan Africa.</p>
<h2>What our review found</h2>
<p>The studies we reviewed indicated that patterns of rainfall, temperature and extreme weather events have changed significantly in the region. This trend is not expected to change in future decades.</p>
<p>Sub-Saharan Africa experiences <a href="https://www.sciencedirect.com/science/article/abs/pii/S0959652623016451">diverse rainfall patterns</a>. Annual rainfall can be as low as 100 millimetres in arid areas in the Sahel and parts of east Africa and over 500 millimetres in tropical areas in central and western Africa. </p>
<p>Temperatures can often exceed 40°C (104°F) during the hottest months. Over the last century, the mean temperature has <a href="https://www.sciencedirect.com/science/article/pii/S2405880722000292">increased</a> by about 0.74°C. </p>
<p>The region <a href="https://www.sciencedirect.com/science/article/pii/S2405880722000292">experiences</a> various extreme weather events, including droughts, floods and heatwaves. Coastal areas, especially in the eastern and southern regions, experience <a href="https://africacenter.org/spotlight/cyclones-more-frequent-storms-threaten-africa/">cyclones or tropical storms</a>.</p>
<p>Many studies show that these conditions affect agricultural production and society in a number of ways:</p>
<ol>
<li><p>Yield reduction: Climate change reduces crop yield. Higher temperatures, changing rainfall patterns, droughts and floods affect harvests. For instance, farmers in Nigeria have seen lower yields caused by new pests, disease outbreaks and the drying up of rivers. </p></li>
<li><p>Food insecurity: Poor agricultural productivity often leads to food insecurity, which affects both rural and urban populations. Lower crop yields can cause prices to rise. Reduced access to food can worsen malnutrition and hunger.</p></li>
<li><p>Income loss and poverty: Lower agricultural output affects the income of smallholder farmers. This can increase poverty levels and economic vulnerability. We found a decline in cereal production over the last decade in Ghana, Congo and South Africa. </p></li>
<li><p>Decreased livestock productivity: Higher temperatures, changes in forage availability, and water scarcity are a challenge for livestock farmers. These make livestock prone to diseases and death. Farmers incur high costs to immunise and treat animals.</p></li>
<li><p>Vulnerability of smallholder farmers: These farmers don’t always have the resources and capacity to adapt to the impact of climate change.</p></li>
</ol>
<h2>Recommendation and policy implications</h2>
<p>The review of studies showed that sub-Saharan Africa could develop economically if rural farmers took more effective measures against climate change.</p>
<p>We made the following recommendations to protect farmers from the impact of climate change:</p>
<ul>
<li><p>Strengthen institutions for policy development and implementation. Coordinating climate change adaptation efforts and sustainable agricultural practices improves farm productivity. </p></li>
<li><p>Improve rural infrastructure. This would promote economic growth, reduce poverty and make rural communities more resilient. </p></li>
<li><p>Initiate public welfare programmes. Improved access to finance, markets, education and climate information would enhance social protection.</p></li>
<li><p>Establish more forest plantations and maintain existing ones. They would help absorb the impact of climate change on agriculture and promote economic development.</p></li>
<li><p>Afforestation and reforestation can also help absorb carbon and conserve biodiversity.</p></li>
</ul><img src="https://counter.theconversation.com/content/215631/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Abeeb Babatunde Omotoso. Researcher at Oyo State College of Agriculture and Technology, Igboora, Nigeria </span></em></p><p class="fine-print"><em><span>Abiodun Olusola Omotayo receives funding from The Climap Africa programme,German Academic Exchange Service (DAAD-Grant Ref: 91838393), Germany and the National Research Foundation’s (NRF), Incentive Funding for Rated Researchers (Grant number: 151680), South Africa. </span></em></p>Smallholder farmers are bearing the brunt of climate change in sub-Saharan Africa. Deliberate steps are required to support them and boost agricultural output,Abeeb Babatunde Omotoso, Postdoctoral research associate, North-West UniversityAbiodun Olusola Omotayo, Senior lecturer/researcher, North-West UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2170682023-11-06T13:33:51Z2023-11-06T13:33:51ZHow global warming shakes the Earth: Seismic data show ocean waves gaining strength as the planet warms<figure><img src="https://images.theconversation.com/files/557584/original/file-20231104-23-ehsyya.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C7998%2C5268&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Storm Ciarán pounded England's Newhaven Lighthouse and harbor wall on Nov. 4, 2023.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/BritainEuropeWeather/ca5dffe836424095b080ee781886aa54/photo">AP Photo/Kin Cheung</a></span></figcaption></figure><p>As oceans waves rise and fall, they apply forces to the sea floor below and generate seismic waves. These seismic waves are so powerful and widespread that they show up as a steady thrum on seismographs, the same instruments used to monitor and study earthquakes.</p>
<p>That wave signal has been getting more intense in recent decades, reflecting increasingly stormy seas and higher ocean swell. </p>
<p>In a <a href="https://doi.org/10.1038/s41467-023-42673-w">new study</a> in the journal Nature Communications, colleagues and I tracked that increase around the world over the past four decades. These global data, along with other ocean, satellite and regional seismic studies, show a decadeslong increase in wave energy that coincides with increasing storminess attributed to rising global temperatures.</p>
<h2>What seismology has to do with ocean waves</h2>
<p>Global seismographic networks are best known for monitoring and studying earthquakes and for allowing scientists to <a href="https://doi.org/10.1029/2021RG000749">create images</a> of the planet’s deep interior.</p>
<p>These <a href="https://www.usgs.gov/faqs/seismometers-seismographs-seismograms-whats-difference-how-do-they-work#">highly sensitive instruments</a> continuously record an enormous variety of natural and human-caused seismic phenomena, including volcanic eruptions, nuclear and other explosions, meteor strikes, landslides and <a href="https://eos.org/editor-highlights/small-seismic-signals-tell-a-story-of-iceberg-calving">glacier-quakes</a>. They also capture persistent seismic signals from wind, water and human activity. For example, seismographic networks observed the global quieting in human-caused seismic noise as lockdown measures were instituted around the world <a href="https://theconversation.com/coronavirus-lockdown-reduced-seismic-activity-around-the-world-new-study-143203">during the coronavirus pandemic</a>.</p>
<p>However, the most globally pervasive of seismic background signals is the incessant thrum created by storm-driven ocean waves referred to as the global microseism.</p>
<h2>Two types of seismic signals</h2>
<p>Ocean waves generate microseismic signals in <a href="https://doi.org/10.1002/2014GL062782">two different ways</a>.</p>
<p>The most energetic of the two, known as the <a href="https://doi.org/10.1002/2014GL062782">secondary microseism</a>, throbs at a period between about eight and 14 seconds. As sets of waves travel across the oceans in various directions, they interfere with one another, creating pressure variation on the sea floor. However, interfering waves aren’t always present, so in this sense, it is an imperfect proxy for overall ocean wave activity.</p>
<p>A second way in which ocean waves generate global seismic signals is <a href="https://earthenvironmentcommunity.nature.com/posts/increasing-ocean-wave-energy-observed-in-earth-s-seismic-wavefield-since-the-late-20th-century">called the primary microseism process</a>. These signals are caused by traveling ocean waves directly pushing and pulling on the seafloor. Since water motions within waves fall off rapidly with depth, this occurs in regions where water depths are less than about 1,000 feet (about 300 meters). The primary microseism signal is visible in seismic data as a steady hum with a period between 14 and 20 seconds.</p>
<h2>What the shaking planet tells us</h2>
<p><a href="https://doi.org/10.1038/s41467-023-42673-w">In our study</a>, we estimated and analyzed historical primary microseism intensity back to the late 1980s at 52 <a href="https://www.usgs.gov/programs/earthquake-hazards/gsn-global-seismographic-network">seismograph sites around the world</a> with long histories of continuous recording.</p>
<p>We found that 41 (79%) of these stations showed highly significant and progressive increases in energy over the decades.</p>
<p>The results indicate that globally averaged ocean wave energy since the late 20th century has increased at a median rate of 0.27% per year. However, since 2000, that globally averaged increase in the rate has risen by 0.35% per year.</p>
<figure><img src="https://cdn.theconversation.com/static_files/files/2894/ocean-wave-intensification-since-late-1980s_rick-aster.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=720&fit=crop&dpr=2"><figcaption>Ocean wave intensification since the late 1980s: Each circle is a seismic station, with size proportional to the vertical acceleration of the Earth at that station smoothed over three years. Red circles indicate periods when ground motions are larger than the historical median; blue indicate periods when they are smaller. The synchronized graph shows the median vertical acceleration anomaly for all stations and reflects El Niño cycles and a more pronounced increase in recent years. Source: Rick Aster</figcaption></figure>
<p>We found the greatest overall microseism energy in the very stormy Southern Ocean regions near the Antarctica peninsula. But these results show that North Atlantic waves have intensified the fastest in recent decades compared to historical levels. That is consistent with recent research suggesting <a href="https://wcd.copernicus.org/articles/3/337/2022/0">North Atlantic storm intensity</a> and <a href="https://doi.org/10.1029/2022GL101963">coastal hazards</a> are increasing. <a href="https://apnews.com/article/storm-ciaran-uk-france-winds-climate-61b722101874e7f0610961c03c509229#">Storm Ciarán</a>, which hit Europe with powerful waves and hurricane-force winds in November 2023, was one record-breaking example.</p>
<p>The decadeslong microseism record also shows the seasonal swing of strong winter storms between the Northern and Southern hemispheres. It captures the wave-dampening effects of growing and shrinking Antarctic sea ice, as well as the multi-year highs and lows associated with El Niño and La Niña cycles and their long-range effects on ocean waves and storms.</p>
<figure class="align-center ">
<img alt="Homes hang over the edge of a cliff above an ocean beach." src="https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557585/original/file-20231104-19-p6vlng.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In November 2022, Hurricane Nicole’s intense waves eroded the land beneath several homes in Daytona Beach, Fla.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/TropicalWeatherFlorida/29f6d284206848159c921b6b84927799/photo">AP Photo/Rebecca Blackwell</a></span>
</figcaption>
</figure>
<p>Together, these and <a href="https://www.universityofcalifornia.edu/news/californias-winter-waves-may-be-increasing-under-climate-change">other recent seismic studies</a> complement the results from climate and ocean research showing that storms, and waves, are intensifying as the climate warms.</p>
<h2>A coastal warning</h2>
<p>The oceans have absorbed about <a href="https://climate.nasa.gov/vital-signs/ocean-warming/">90% of the excess heat</a> connected to rising greenhouse gas emissions from human activities in recent decades. That excess energy can translate into <a href="https://doi.org/10.1038/s41467-018-08066-0">more damaging waves and more powerful storms</a>.</p>
<p>Our results offer another <a href="https://theconversation.com/dreaming-of-beachfront-real-estate-much-of-floridas-coast-is-at-risk-of-storm-erosion-that-can-cause-homes-to-collapse-as-daytona-just-saw-194492">warning for coastal communities</a>, where increasing ocean wave heights can pound coastlines, damaging infrastructure and <a href="https://www.usgs.gov/science/science-explorer/climate/coasts-storms-and-sea-level-rise">eroding the land</a>. The impacts of increasing wave energy are further compounded by ongoing <a href="https://toolkit.climate.gov/topics/coastal-flood-risk/coastal-erosion">sea level rise</a> fueled by climate change and by subsidence. And they emphasize the importance of mitigating climate change and building resilience into coastal infrastructure and environmental protection strategies.</p><img src="https://counter.theconversation.com/content/217068/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Aster receives funding from the U.S. National Science Foundation.</span></em></p>The same instruments used to measure earthquakes pick up vibrations as ocean waves put pressure on the sea floor. Four decades of data tell a story about ocean storms.Richard Aster, Professor of Geophysics and Department Head, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2119532023-08-24T14:11:26Z2023-08-24T14:11:26ZWorld’s beaches are changing because of climate change - green thinking is needed to save them<p>Coastlines – the interface between land and sea – lie at the frontline in the battle against climate change impacts. </p>
<p><a href="https://www.cambridge.org/core/journals/cambridge-prisms-coastal-futures/article/population-development-as-a-driver-of-coastal-risk-current-trends-and-future-pathways/8261D3B34F6114EA0999FAA597D5F2E2">Globally</a>, almost 1 billion people now live within 10km of a coastline and the same number live in areas less than 10 metres above sea level. These populations face some of the world’s biggest climate hazards, such as coastal floods from rising sea levels and the effects of hurricanes and tropical storms, which are <a href="https://journals.ametsoc.org/view/journals/wcas/2/4/2010wcas1050_1.xml">becoming more frequent and deadly</a>. If there is a 2 metre increase in sea levels by 2100, this may lead to the <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2010.0291#RSTA20100291F2">forced migration</a> of between 72 million and 187 million people. </p>
<p>However, coastlines vary substantially in their physical properties, and are found across all latitudes, environments and with a range of ecosystems and types of human activity. This means that coastline responses to climate change will vary from one place to another.</p>
<p>Several studies have identified sandy coastlines as particularly vulnerable to climate change, because they are made up of loose sand grains that are easily eroded by waves. A <a href="https://www.nature.com/articles/s41598-018-24630-6">survey</a> in 2018 showed that 24% of sandy coasts globally were already experiencing persistent net erosion because of climate change, and this was projected to get even worse in the future. </p>
<p>This is of concern because sandy coasts are <a href="https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-3/">particularly important</a> for biodiversity, carbon storage, agriculture and tourism. </p>
<p>In a recent <a href="https://www.tandfonline.com/doi/full/10.1080/03736245.2023.2193565">study</a> of South African coastlines I examined the properties that contribute to their physical and biological resilience. Coastal landforms (features like estuaries, barrier islands, beaches and sand dunes) can buffer the effects of climate change and provide ecosystem and environmental services. Viewing coastal landforms as “green infrastructure” is a way to work with nature to manage the impacts of climate change.</p>
<h2>Managing coastlines to boost resilience</h2>
<p>Not all sandy coastlines respond in the same ways to climate, in part because they are made up of different landforms. Research shows that these landforms <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL087862">respond in different ways</a> to waves, tides, sea-level change and sediment supply. </p>
<p>Their varied behaviours mean that a range of management responses are required to limit the impacts of climate change on these landforms, and this is the challenge facing all coasts globally in the 21st century. </p>
<p>However, there are some problems. Many management approaches used in the past are inappropriate or have actually made the situation worse. A classic example is where a sea wall or revetment is built along an eroding sandy coastline. This is usually a hard, high, straight structure, often built of concrete and designed to stabilise the coastline and keep the sea out. These structures often focus rather than disperse incoming wave energy, leading to increased beach erosion and undercutting of the sea wall, and requiring further and bigger structures to be built as the coast erodes even faster. Many such engineering structures designed to protect coasts are expensive, require continuous maintenance, and may have similar unintended consequences. Thus, these structures often make coastal problems worse, not better. </p>
<p>Instead, different approaches are needed. Working with – and not against – the natural processes and landforms that already exist along sandy coastlines may be a more effective and cheaper option. This is where natural beaches or sand dunes may protect the land against coastal erosion and be maintained by natural ecological and sedimentary processes. </p>
<p>In <a href="https://www.tandfonline.com/doi/full/10.1080/03736245.2023.2193565">my study</a>, I have shown how the natural landforms of different coastal environments can serve as green infrastructure: natural features that perform the same function as hard engineering structures in coastal protection. Natural beaches or sand dunes can stabilise the land surface and reduce erosion rates, provide ecosystem services and maintain biodiversity, store organic carbon, modify microclimate, and reduce the impacts of coastal hazards on local communities. </p>
<p>However, this approach has not been commonly used along African coasts, despite its <a href="https://link.springer.com/article/10.1007/s10113-019-01508-5">environmental benefits</a>. </p>
<p>Using coastal landforms as green infrastructure can build coastal resilience to climate change. This is a “win-win” situation for both coastal landforms and populations.</p>
<h2>Green infrastructure</h2>
<p>Green infrastructure is part of wider <a href="https://wayback.archive-it.org/12090/20230308081805/https:/ec.europa.eu/environment/integration/green_semester/pdf/Recreate_PB_2015_NBS_final_druck10-02-2016.pdf">nature-based solutions</a> to addressing environmental issues and climate change impacts. However, a number of developments are needed to make the use of green infrastructure a wider practice, but local authorities, planners and managers. </p>
<p>Coastlines need to be recognised as naturally dynamic, shifting environments rather than as environments that need to be controlled and managed. The multiple and varied benefits that coastlines give to the environment, ecosystems and people must be recognised, including how they relate to one another. </p>
<p>Coastlines therefore need to be considered as integrated and dynamic systems, not simply as the boundaries between land and sea. </p>
<p>And finally, not all coastlines are the same – sandy and rocky coastlines work in different ways, as do coral reef, mangrove or glaciated coasts. This means that each coastline has different elements that contribute to their overall resilience or vulnerability to climate change impacts.</p><img src="https://counter.theconversation.com/content/211953/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jasper Knight does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Coastlines need to be recognised as dynamic, shifting environments rather than as environments that need to be controlled and managed.Jasper Knight, Professor of Physical Geography, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2095932023-08-10T03:24:09Z2023-08-10T03:24:09ZNew evidence suggests the world’s largest known asteroid impact structure is buried deep in southeast Australia<figure><img src="https://images.theconversation.com/files/542059/original/file-20230810-25-7n4kt.png?ixlib=rb-1.1.0&rect=43%2C0%2C2600%2C1005&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Google Maps</span></span></figcaption></figure><p><em>Acknowledgment: I’d like to thank my colleague Tony Yeates, who originated the view of the Deniliquin multi-ring structure as an impact structure – and who was instrumental to this work.</em></p>
<p>In <a href="https://www.sciencedirect.com/science/article/abs/pii/S0040195122002487">recent research</a> published by myself and my colleague Tony Yeates in the journal Tectonophysics, we investigate what we believe – based on many years of experience in asteroid impact research – is the world’s largest known impact structure, buried deep in the earth in southern New South Wales.</p>
<p>The Deniliquin structure, yet to be further tested by drilling, spans up to 520 kilometres in diameter. This exceeds the size of the near-300km-wide <a href="https://en.wikipedia.org/wiki/Vredefort_impact_structure">Vredefort</a> impact structure in South Africa, which to date has been considered the world’s largest.</p>
<h2>Hidden traces of Earth’s early history</h2>
<p>The history of Earth’s bombardment by asteroids is largely concealed. There are a few reasons for this. The first is erosion: the process by which gravity, wind and water slowly wear away land materials through time. </p>
<p>When an asteroid strikes, it creates a crater with an uplifted core. This is similar to how a drop of water splashes upward from a transient crater when you drop a pebble in a pool. </p>
<p>This central uplifted dome is a key characteristic of large impact structures. However, it can erode over thousands to millions of years, making the structure difficult to identify.</p>
<p>Structures can also be buried by sediment through time. Or they might disappear as a result of subduction, wherein tectonic plates can collide and slide below one another into Earth’s mantle layer.</p>
<p>Nonetheless, new geophysical discoveries are unearthing signatures of impact structures formed by asteroids that may have reached tens of kilometres across – heralding a paradigm shift in our understanding of how Earth evolved over eons. These include pioneering discoveries of impact “ejecta”, which are the materials thrown out of a crater during an impact. </p>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S1387647317300714">Researchers think</a> the oldest layers of these ejecta, found in sediments in early terrains around the world, might signify the tail end of the Late Heavy Bombardment of Earth. The <a href="https://www.sciencedirect.com/science/article/abs/pii/S1387647317300714">latest evidence</a> suggests Earth and the other planets in the Solar System were subject to intense asteroid bombardments until about 3.2 billion years ago, and sporadically since.</p>
<p>Some large impacts are correlated with mass extinction events. For example, the <a href="https://en.wikipedia.org/wiki/Alvarez_hypothesis">Alvarez hypothesis</a>, named after father and son scientists Luis and Walter Alvarez, explains how non-avian dinosaurs were wiped out as a result of a large asteroid strike some 66 million years ago.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-found-the-worlds-oldest-asteroid-strike-in-western-australia-it-might-have-triggered-a-global-thaw-130192">We found the world's oldest asteroid strike in Western Australia. It might have triggered a global thaw</a>
</strong>
</em>
</p>
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<h2>Uncovering the Deniliquin structure</h2>
<p>The Australian continent and its predecessor continent, <a href="https://en.wikipedia.org/wiki/Gondwana">Gondwana</a>, have been the target of numerous asteroid impacts. These have resulted in at least 38 confirmed and 43 potential impact structures, ranging from relatively small craters to large and completely buried structures.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=516&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=516&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=516&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=649&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=649&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=649&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This map shows the distribution of circular structures of uncertain, possible or probable impact origin on the Australian continent and offshore. Green dots represent confirmed impact craters. Red dots represent confirmed impact structures that are more than 100km wide, whereas red dots inside white circles are more than 50km wide. Yellow dots represent likely impact structures.</span>
<span class="attribution"><span class="source">Andrew Glikson and Franco Pirajno</span></span>
</figcaption>
</figure>
<p>As you’ll recall with the pool and pebble analogy, when a large asteroid hits Earth, the underlying crust responds with a transient elastic rebound that produces <a href="https://www.lpi.usra.edu/publications/books/CB-954/CB-954.pdf">a central dome</a>. </p>
<p>Such domes, which can slowly erode and/or become buried through time, may be all that’s preserved from the original impact structure. They represent the deep-seated “root zone” of an impact. Famous examples are found in the Vredefort impact structure and the 170km-wide <a href="https://en.wikipedia.org/wiki/Chicxulub_crater">Chicxulub crater</a> in Mexico. The latter represents the impact that caused the extinction of the dinosaurs.</p>
<p>Between 1995 and 2000, Tony Yeates suggested magnetic patterns beneath the Murray Basin in New South Wales <a href="https://www.aseg.org.au/publications/preview-old">likely represented</a> a massive, buried impact structure. An analysis of the region’s updated geophysical data between 2015 and 2020 confirmed the existence of a 520km diameter structure with a seismically defined dome at its centre.</p>
<p>The Deniliquin structure has all the features that would be expected from a large-scale impact structure. For instance, magnetic readings of the area reveal a symmetrical rippling pattern in the crust around the structure’s core. This was likely produced during the impact as extremely high temperatures created intense magnetic forces.</p>
<p>A central low magnetic zone corresponds to 30km-deep deformation above a seismically defined mantle dome. The top of this dome is about 10km <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL065345">shallower than the top</a> of the regional mantle.</p>
<p>Magnetic measurements also show evidence of “radial faults”: fractures that radiate from the centre of a large impact structure. This is further accompanied by small magnetic anomalies which may represent igneous “dikes”, which are sheets of magma injected into fractures in a pre-existing body of rock. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=565&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=565&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=565&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=710&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=710&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=710&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This ‘total magnetic intensity’ image of the Deniliquin impact structure portrays its 520km-diameter multi-ring pattern, the central core, radial faults and the location of shallow drill holes.</span>
<span class="attribution"><a class="source" href="https://www.sciencedirect.com/science/article/abs/pii/S0040195122002487">Data from Geoscience Australia, published in Glikson and Yeates, 2022</a></span>
</figcaption>
</figure>
<p>Radial faults, and igneous sheets of rocks that form within them, are typical of large impact structures and can be found in the Vredefort structure and the <a href="https://journals.uair.arizona.edu/index.php/maps/article/viewFile/14921/14892">Sudbury impact structure</a> in Canada.</p>
<p>Currently, the bulk of the evidence for the Deniliquin impact is based on geophysical data obtained from the surface. For proof of impact, we’ll need to collect physical evidence of shock, which can only come from drilling deep into the structure.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/these-5-spectacular-impact-craters-on-earth-highlight-our-planets-wild-history-197618">These 5 spectacular impact craters on Earth highlight our planet's wild history</a>
</strong>
</em>
</p>
<hr>
<h2>When did the Deniliquin impact happen?</h2>
<p>The Deniliquin structure was likely located on the eastern part of the Gondwana continent, prior to it splitting off into several continents (including the Australian continent) much later.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=432&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=432&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=432&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Deniliquin structure was likely created in eastern Gondwana during the Late Ordovician.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-022-08941-3#rightslink">Zhen Qiu et al, 2022</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The impact that caused it may have occurred during what’s known as the Late Ordovician mass extinction event. Specifically, I think it may have triggered what’s called the <a href="https://www.britannica.com/science/Ordovician-Silurian-extinction">Hirnantian glaciation stage</a>, which lasted between 445.2 and 443.8 million years ago, and is also defined as the <a href="https://www.sciencedirect.com/science/article/abs/pii/S1342937X23000655">Ordovician-Silurian extinction event</a>. </p>
<p>This huge glaciation and mass extinction event <a href="https://www.britannica.com/science/Ordovician-Silurian-extinction">eliminated</a> about 85% of the planet’s species. It was more than double the scale of the <a href="https://en.wikipedia.org/wiki/Alvarez_hypothesis">Chicxulub impact</a> that killed off the dinosaurs. </p>
<p>It is also possible the Deniliquin structure is older than the Hirnantian event, and may be of an early Cambrian origin (about 514 million years ago). The next step will be to gather samples to determine the structure’s exact age. This will require drilling a deep hole into its magnetic centre and dating the extracted material. </p>
<p>It’s hoped further studies of the Deniliquin impact structure will shed new light on the nature of early <a href="https://www.livescience.com/37584-paleozoic-era.html">Paleozoic</a> Earth.</p><img src="https://counter.theconversation.com/content/209593/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Glikson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Research on the Deniliquin structure points to an asteroid impact that would have been more than double the scale of the one that killed the dinosaurs.Andrew Glikson, Adjunct professor, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2064432023-06-27T14:52:51Z2023-06-27T14:52:51ZWe have forgotten what a ‘natural’ river even looks like<figure><img src="https://images.theconversation.com/files/534107/original/file-20230626-17-zp01fc.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C3986%2C2527&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Thames is placed in a straitjacket long before London.</span> <span class="attribution"><span class="source">photocritical / shutterstock</span></span></figcaption></figure><p>Britain’s rivers are under the spotlight because of an untreated <a href="https://theconversation.com/sewage-pollution-why-the-uk-water-industry-is-broken-186762">sewage crisis</a>, and the pendulum of <a href="https://theconversation.com/floods-are-going-to-get-worse-we-need-to-start-preparing-for-them-now-172902">floods</a> and <a href="https://theconversation.com/why-the-drought-isnt-over-even-though-its-rained-all-week-190812">droughts</a> that are the hallmark of a warming world. But hidden within these policy debates is a pervasive and under reported issue: quite simply, people have forgotten what a natural river even looks like. </p>
<p>This is important because it underpins attitudes towards the kind of rivers people expect to live with, and therefore constrains the changes to rivers that people will be willing to accept. Scientific evidence says radically different looking rivers are needed in order to accommodate larger, more frequent floods and droughts, to deliver increases in biodiversity, and to store more carbon.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Annotated map of england and wales" src="https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=808&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=808&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=808&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1015&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1015&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534334/original/file-20230627-26805-7mwt03.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1015&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rivers and streams are relatively free in blue and green areas, but heavily modified in orange and red.</span>
<span class="attribution"><span class="source">Naura, M. (2017) Mapping Channel Re-sectioning in England and Wales, Internal Report for the Environment Agency.</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Why have we forgotten what our natural rivers look like? In the UK and most other developed economies, the network of streams and rivers have been managed, and physically altered in some cases, for more than 1,000 years to support more farms and later more industry.</p>
<p>It is no wonder most people do not realise that the rivers they grew up with, fish in, swim in, or simply walk along are nothing like the natural ecosystems they once were. History and culture has evolved around modified river systems. </p>
<p>In Britain, for instance, 1,000 years of change has meant <a href="https://www.sciencedirect.com/science/article/pii/S0048969719316511">97% of rivers are fragmented</a> by barriers like weirs. Things accelerated after World War I with 36% of the river network of England and Wales, some 35,500km, subject to <a href="https://www.sciencedirect.com/science/article/pii/0048969783901493">major modifications</a>. And these are only the documented changes – much more was routinely maintained such as the annual removal of silt or vegetation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Barrier in river in countryside" src="https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534205/original/file-20230627-15-tczhss.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Weirs our natural river gone? Almost every river has at least one barrier like this.</span>
<span class="attribution"><span class="source">JoeEJ / shutterstock</span></span>
</figcaption>
</figure>
<p>In the early 1990s, I visited every flood defence office in England and Wales as part of <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/esp.3290200706">a study</a> asking how much sediment is removed from rivers, how expensive it was and why we were doing it. It became clear that it was costly and in many cases it was done simply because “that is what happens on October 15” – and woe betide you if you were late because the locals expected it. This expectation of river cleansing is still apparent today in calls to <a href="https://www.somersetcountygazette.co.uk/news/22315981.extra-funding-agreed-dredging-somerset-levels/">dredge rivers</a> after a major flood or sometimes to <a href="https://www.bbc.co.uk/news/uk-england-cumbria-35999855">push gravel back into them</a>. </p>
<p>There has been some increase in river restoration (or “re-wiggling”) with more than 2,500km restored in the UK <a href="https://www.therrc.co.uk/sites/default/files/files/Conference/2022/Presentations/rrc_keynote_2022_final2_david_sear.pdf">since the early 1990s</a>. However, this represents less than 3% of the highly damaged river network and much more needs to be done. Though the sewage crisis dominates headlines in the UK, the physical modification of rivers matters too. </p>
<h2>Physical form of a river</h2>
<p>The “look” of a river isn’t just aesthetics – things like the number and shape of channels, gravel shoals and sandbanks, or the presence of vegetation or an eroding riverbank all affect how it acts as an ecosystem. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="River flooding into field with trees" src="https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534547/original/file-20230628-19-am2kno.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When given space and allowed to do its thing, a natural river can look ‘messy’.</span>
<span class="attribution"><span class="source">David Sear</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>More complex and “messy” rivers tend to store and slow down the flows of water, sediments and nutrients. This creates a better habitat for plants and animals. It also means these rivers don’t strip as many nutrients from the surrounding landscape, and are able to store more carbon in the form of living and dead plants (as peat, for example). Messy rivers release water slowly like a sponge, protecting against both floods and droughts. </p>
<p>That said, modified rivers can provide efficient transport of bulk goods via shipping, in some cases they can protect from floods and provide hydroelectricity and food security for millions of people. The restoration of more natural rivers therefore involves trade-offs. As far back as 2004, a <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/300332/04-947-flooding-summary.pdf">government report</a> concluded that the UK needed to do something other than build higher and more expensive flood defences in the face of a future of more extreme and frequent floods. But too often the multiple benefits provided by more natural rivers are ignored in these discussions. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Neil Mitchell" src="https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534337/original/file-20230627-23-6pipr1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">River or canal? The River Dee near Chester certainly didn’t look like this before humans came along.</span>
<span class="attribution"><span class="source">Neil Mitchell / shutterstock</span></span>
</figcaption>
</figure>
<p>One option is to work more with nature to deliver benefits from our rivers and floodplains that are not simply based on food security, home building or flood protection. People want to engage with nature and recent studies show that it is <a href="https://theconversation.com/living-near-water-can-be-beneficial-to-your-mental-health-heres-how-to-have-more-blue-spaces-in-cities-150486">good for us</a>. But first we must learn to tell the story of how our rivers came to look the way they do, and why natural rivers can be beneficial for all of us. At the very least a better understanding of what we have lost and what the alternatives could be will offer a more balanced argument for or against more natural rivers. </p>
<p>Britain’s “riverscape” is the product of centuries of modification. Some of this is here to stay – no one is suggesting turning London back into a floodplain, for instance, and we still need food and to protect properties. But we also need a more sophisticated understanding of why allowing some rivers to return to their natural form and processes is vital to our future and to the future of our ecosystems.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
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<p class="fine-print"><em><span>David Sear does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>In praise of messy rivers.David Sear, Professor in Physical Geography, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2050092023-05-23T12:27:30Z2023-05-23T12:27:30ZMore than two dozen cities and states are suing Big Oil over climate change – they just got a boost from the US Supreme Court<p>Honolulu has lost <a href="https://s3.documentcloud.org/documents/6801979/Honolulu-Climate-Lawsuit-3-9-2020.pdf">more than 5 miles</a> of its famous beaches to sea level rise and storm surges. Sunny-day flooding during high tides makes many city roads impassable, and water mains for the public drinking water system are corroding from saltwater because of sea level rise.</p>
<p>The damage has left the city and county spending millions of dollars on repairs and infrastructure to try to adapt to the rising risks.</p>
<p>Future costs will almost certainly be higher. More than US$19 billion in property value, at today’s dollars, is at risk by 2100 from projected sea level rise, driven by greenhouse gas emissions largely from the burning of fossil fuels. Elsewhere in Honolulu County, which covers all of Oahu, many coastal communities will be cut off or uninhabitable.</p>
<p>Unwilling to have their taxpayers bear the full brunt of these costs, the <a href="https://s3.documentcloud.org/documents/6801979/Honolulu-Climate-Lawsuit-3-9-2020.pdf">city and county sued</a> Sunoco LP, Exxon Mobil Corp. and other big oil companies in 2020.</p>
<p>Their case – one of <a href="https://climateintegrity.org/cases">more than two dozen</a> involving <a href="https://images.theconversation.com/files/527655/original/file-20230523-14019-49gxsv.png">U.S. cities, counties and states suing the oil industry</a> over climate change – just got a break from the U.S. Supreme Court. That has significantly increased their odds of succeeding.</p>
<h2>Suing over the cost of climate change</h2>
<p>At stake in all of these cases is who pays for the staggering cost of a changing climate.</p>
<p>Local and state governments that are suing want to hold the major oil companies responsible for the costs of responding to disasters that scientists are increasingly <a href="https://news.climate.columbia.edu/2021/10/04/attribution-science-linking-climate-change-to-extreme-weather/">able to attribute</a> to climate disruption and <a href="https://doi.org/10.1088/1748-9326/acbce8">tie back to the fossil fuel industry</a>. Several of the plaintiffs accuse the companies of lying to the public about their products’ risks in violation of state or local consumer protection laws that prohibit false advertising.</p>
<p><iframe id="j1ckJ" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/j1ckJ/20/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The governments in the <a href="https://s3.documentcloud.org/documents/6801979/Honolulu-Climate-Lawsuit-3-9-2020.pdf">Honolulu case allege</a> that the oil companies “are directly responsible” for a substantial rise in carbon dioxide emissions that have been driving climate change. They say the companies should contribute their <a href="https://commonwealthmagazine.org/energy/fair-share-for-the-fossil-fuel-industry/">fair share</a> to defray some of the costs.</p>
<p>The gist of Honolulu’s complaint is that the big oil companies <a href="https://www.science.org/doi/10.1126/science.abk0063">have known for decades</a> that their products cause climate change, yet their public statements continued to <a href="https://theconversation.com/what-big-oil-knew-about-climate-change-in-its-own-words-170642">sow doubts</a> about <a href="https://theconversation.com/i-was-an-exxon-funded-climate-scientist-49855">what was known</a>, and they failed to warn their customers, investors and the public about the dangers posed by their products. </p>
<p>Were it not for this deception, the lawsuit says, the city and county would not be facing mounting costs of abating the damage from climate change.</p>
<p>Importantly, the complaint is based on state – not federal – law. It alleges that the defendants have violated established common law rules long recognized by the courts involving nuisance, failure to warn and trespass.</p>
<p>The city and county want the companies to help fund climate adaptation measures – everything from building seawalls and raising buildings to buying flood-prone properties and restoring beaches and dunes.</p>
<h2>Supreme Court could have killed these cases</h2>
<p>Not surprisingly, the oil companies have thrown their vast legal resources into fighting these cases.</p>
<p>On April 24, however, they lost one of their most powerful arguments.</p>
<p>The U.S. Supreme Court <a href="https://www.supremecourt.gov/orders/courtorders/042423zor_1p24.pdf">declined to hear challenges</a> in the Hawaii case and four others involving the seemingly technical question of which court should hear these cases: state or federal.</p>
<p>The oil companies had “<a href="https://www.bonalaw.com/insights/legal-resources/requirements-for-removing-a-case-from-state-court-to-federal-court">removed</a>” the cases from state court to federal court, <a href="http://climatecasechart.com/case/city-county-of-honolulu-v-sunoco-lp/">arguing that damage lawsuits</a> for climate change go beyond the limits of state law and are governed by federal law. </p>
<p>That theory would have derailed all five cases – because there is no federal common law for greenhouse gases.</p>
<p>The court made that position clear in 2011 in <a href="https://www.oyez.org/cases/2010/10-174">American Electric Power Co. v. Connecticut</a>. Several state and local governments had sued five major power companies for violating the federal common law of interstate nuisance and asked for a court order forcing these companies to reduce their emissions. The Supreme Court refused, holding that the federal Clean Air Act displaced federal common law for these gases. </p>
<p>In <a href="https://law.justia.com/cases/federal/appellate-courts/ca9/09-17490/09-17490-2012-09-21.html">Native Village of Kivalina v. Exxon Mobil Corp.</a>, a federal court of appeals extended that holding to also bar claims for monetary damages based on federal common law.</p>
<figure class="align-center ">
<img alt="Sandbags sit outside a home near a beach in Oahu, Hawaii, where waves have eaten into the shoreline almost up to the house." src="https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527383/original/file-20230521-128284-x96kaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Several coastal communities, including in Honolulu County, facing increasing erosion want oil companies to help pay for protective infrastructure.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/4c2fc5b90f894fe7963daeb19724bce4?ext=true">AP Photo/Audrey McAvoy</a></span>
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<p>To avoid this fate, Honolulu and the other plaintiffs focused on violations of state law, not federal law. Without exception, the federal courts of appeals sided with them and sent the cases back to state court.</p>
<h2>What happens next?</h2>
<p>The Honolulu case leads the pack at this point.</p>
<p>In 2022, the 1st Circuit Court in Hawaii <a href="http://climatecasechart.com/climate-change-litigation/wp-content/uploads/sites/16/case-documents/2022/20220203_docket-1CCV-20-0000380_ruling.pdf">denied the oil companies’ motion</a> to dismiss the case based on the argument that the Clean Air Act also preempts state common law. This could open the door for discovery to begin sometime this year.</p>
<p>In discovery, senior corporate officers – perhaps including <a href="https://theconversation.com/exxons-rex-tillerson-and-the-rise-of-big-oil-in-american-politics-70260">former Exxon Mobil CEO Rex Tillerson</a>, who was secretary of state under Donald Trump – will be required to answer questions under oath about what the companies knew about climate change versus what they disclosed to the public.</p>
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<img alt="Rex Tillerson, a smiling older man in a suit and tie, walks out of a courthouse with security guards." src="https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527353/original/file-20230521-106641-dkrcqe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">In 2019, former Exxon Mobil CEO Rex Tillerson testified in a securities fraud lawsuit brought by the New York attorney general’s office. The judge ruled in Exxon’s favor.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/ExxonClimateLawsuit/cc7e743167614cb4bf7a4ec99319422f/photo">AP Photo/Seth Wenig</a></span>
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<p>Evidence <a href="https://www.science.org/doi/10.1126/science.abk0063">from Exxon documents</a>, described in a recent study by science historians Naomi Oreskes and Geoffrey Supran, shows that the company’s own scientists “knew as much as academic and government scientists knew” about climate change going back decades. But instead of communicating what they knew, “Exxon worked to deny it,” Supran and Oreskes write. The company overemphasized uncertainties and cast doubt on climate models.</p>
<p>This is the kind of evidence that could sway a jury. The standard of proof in a civil case like Honolulu’s is “preponderance of the evidence,” which roughly translates to 51%. Ten of the 12 jurors must agree on a verdict.</p>
<p>Any verdict likely would be appealed, perhaps all the way to the U.S. Supreme Court, and it could be years before the Honolulu case is resolved.</p>
<h2>Lawsuits don’t begin to cover the damage</h2>
<p>It is unlikely that even substantial verdicts in these cases will come close to covering the full costs of damage from climate change.</p>
<p>According to the National Oceanic and Atmospheric Administration, <a href="https://www.climate.gov/news-features/blogs/2022-us-billion-dollar-weather-and-climate-disasters-historical-context">in 2022 alone the U.S. sustained</a> 18 weather and climate disasters that each exceeded $1 billion in damage. Together, they cost over $165 billion.</p>
<p>But for many of the communities most at risk from these disasters, every penny counts. We believe establishing the oil companies’ responsibility may also discourage further investments in fossil fuel production by banks and brokerage houses already nervous about the <a href="https://www.ey.com/en_it/banking-capital-markets-risk-regulatory-transformation/climate-change-and-risk-three-key-challenges-facing-banks">financial risks</a> of climate disruption.</p><img src="https://counter.theconversation.com/content/205009/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Honolulu, Baltimore, Charleston, S.C. and several other cities harmed by rising seas and extreme weather are suing the oil industry. At stake is who pays for the staggering costs of climate change.Patrick Parenteau, Professor of Law Emeritus, Vermont Law & Graduate SchoolJohn Dernbach, Professor of Law, Widener UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2018122023-03-24T09:33:06Z2023-03-24T09:33:06ZWater scarcity on Nigeria’s coast is hardest on women: 6 steps to ease the burden<figure><img src="https://images.theconversation.com/files/516332/original/file-20230320-550-a9q1oa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Luis Tato/AFP via Getty Images</span></span></figcaption></figure><p>Imagine waking up before dawn every day to fetch water for your family. You trek to the nearest water source, miles away, with only a jerrycan to carry the precious liquid. You brave scorching heat or heavy rain, while trying to avoid dangerous animals and strangers along the way.</p>
<p>This is the reality of many women in Nigeria’s coastal areas, particularly in the Ilaje region, Ondo State, south-western Nigeria. Water scarcity is a persistent problem in the region and climate change is making it <a href="https://www.icirnigeria.org/double-woes-oil-spillage-sea-surge-threaten-ilaje-communities/">worse</a>. Women bear the brunt of this crisis, as they are responsible for fetching water, cooking and other household chores. This leaves them little time for other activities, such as education or income-generating work. </p>
<p>The effects of climate change are <a href="https://www.sciencedirect.com/science/article/pii/S2666683920300420">evident</a> in the region. They lead to crop failures, erosion and loss of livelihoods due to extreme weather events such as droughts and floods. The coastal region of Nigeria is particularly at <a href="https://climateknowledgeportal.worldbank.org/country/nigeria/vulnerability">risk</a>, with a projected one-metre rise in sea level potentially resulting in the loss of 75% of the land in the region. Women in the region are especially vulnerable to the effects of climate change. Many rely on farming and fishing for their livelihoods and are responsible for collecting and using water. </p>
<p>We conducted a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0959652619338855">study</a> of vulnerability of women to climate change in the region. This involved focus group discussions with women and men in the community and key informant interviews with local leaders and officials. Our findings showed that women face water scarcity and climate change challenges. They are vulnerable to water-borne diseases and gender-based violence. We also found that women’s participation in water management and decision-making was limited, which affected their ability to influence policies and strategies related to water governance. </p>
<p>To further investigate the vulnerability of women to climate change in Ilaje coastal region, we collected data from 10 coastal communities. Our study found that extreme weather events have been occurring in the region for the past 44 years. The communities were vulnerable to flooding and erosion. Women were particularly vulnerable to climate change impacts because of factors like their economic status, poor education, cultural norms and political marginalisation.</p>
<p>The intersection of gender, climate change and water scarcity creates a complex challenge that demands a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0959652619338855">comprehensive and inclusive approach</a>. There are six steps that would improve the situation. They include governments, civil society organisations and local communities tackling the underlying causes of water scarcity. And involving women in water management and decision-making.</p>
<h2>Nigeria’s water crisis</h2>
<p>Nigeria’s water scarcity crisis is not limited to this region alone. In 2019, <a href="https://www.worldbank.org/en/news/press-release/2021/05/25/improving-water-supply-sanitation-and-hygiene-services-in-nigeria">approximately 60 million Nigerians</a> didn’t have basic drinking water services. Globally, <a href="https://www.who.int/news-room/fact-sheets/detail/drinking-water">122 million people</a> have to collect unsafe water from streams or ponds. <a href="https://www.unicef.org/philippines/press-releases/two-billion-people-lack-safe-drinking-water-more-twice-lack-safe-sanitation">Two billion</a> people lack safe drinking water. Similarly, two out of every five people defecate in the streets or bushes. </p>
<p>According to the <a href="https://www.un.org/sustainabledevelopment/blog/2023/01/ancient-tale-of-hummingbird-inspires-un-world-water-day-campaign/">United Nations</a>, poor water, sanitation and hygiene cause 1.4 million deaths annually and shorten the lives of 74 million people. Nearly <a href="https://factsanddetails.com/world/cat57/sub379/item2168.html">half</a> of all wastewater from households globally, which contains toxic substances from toilets, sinks, drains and gutters, flows back into nature without proper treatment. </p>
<p>The implications of this discharge of toxic substances are especially dire for people who live on coasts, such as those in the Ilaje region in Nigeria. Women and girls are at increased risk of waterborne illnesses because they are often the primary collectors and users of water resources in these communities. </p>
<h2>What can be done</h2>
<p>Governments, civil society organisations and local communities can take the following steps to ensure that their efforts to address water scarcity are gender-sensitive and inclusive:</p>
<p>• Educate and empower women: Education is critical in empowering women to participate in water management and decision-making. <a href="https://www.un.org/waterforlifedecade/pdf/un_water_policy_brief_2_gender.pdf">Building women’s skills and knowledge</a> enables them to take a more active role in addressing the water crisis. </p>
<p>• Involve women in water management and decision-making: Women are often disproportionately affected by water scarcity, as they are responsible for water-fetching, cooking and other household chores. Involving them in decisions can help ensure that their needs and concerns are considered.</p>
<p>• Support women-led start-ups and businesses: Women are often under-represented in entrepreneurship but have unique perspectives and insights that can be used to develop innovative solutions to the water crisis. Supporting women-led startups and businesses can help create a more equitable and sustainable future.</p>
<p>• Provide access to sanitation facilities for women and girls: Lack of access to sanitation facilities can have a <a href="https://blogs.worldbank.org/endpovertyinsouthasia/enhancing-womens-access-water-sanitation-and-hygiene-bangladesh">significant impact</a> on women’s and girl’s <a href="https://www.unicef.org/nigeria/stories/wash-facilities-influence-school-attendance-among-adolescent-girls">education</a>, health, safety and dignity. </p>
<p>• Support women’s groups and initiatives: This can help to ensure that <a href="https://asiapacific.unwomen.org/en/stories/experts-take/2022/06/womens-voice-and-influence">women’s voices</a> are heard and their needs are addressed.</p>
<p>• Address gender-based violence: Violence can <a href="https://www.worldbank.org/en/topic/socialsustainability/brief/violence-against-women-and-girls">hinder</a> women’s access to safe and reliable water resources. Addressing gender-based violence is crucial to ensuring that women and girls can safely access and use water resources.</p><img src="https://counter.theconversation.com/content/201812/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adenike Akinsemolu does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Gender, climate change and water scarcity together create a difficult challenge.Adenike Akinsemolu, Vanguard Fellow, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2000592023-02-16T22:18:22Z2023-02-16T22:18:22ZCyclone Gabrielle triggered more destructive forestry ‘slash’ – NZ must change how it grows trees on fragile land<figure><img src="https://images.theconversation.com/files/510721/original/file-20230216-16-6bc5um.jpg?ixlib=rb-1.1.0&rect=38%2C7%2C5137%2C3437&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Getty Images</span></span></figcaption></figure><p>The severe impacts of Cyclone Gabrielle on the North Island, and the <a href="https://www.rnz.co.nz/news/national/484167/cyclone-gabrielle-thames-coromandel-already-facing-fifth-severe-weather-event-of-year">five severe weather events</a> experienced by the Thames–Coromandel region in just the first two months of 2023, are merely the latest examples of more frequent erosion-triggering rainfall events over the past decade.</p>
<p>Inevitably with the heavy rain, soil, rocks and woody material (also known as “slash”) from landslides have flowed down onto valleys and flood plains, damaging the environment and risking <a href="https://www.newshub.co.nz/home/new-zealand/2023/01/wellington-boy-dies-after-injury-involving-forestry-slash-at-gisborne-beach.html">human safety</a>. </p>
<p>Clear-fell harvesting of pine forests on steep erosion-prone land has been identified as a key source of this phenomenon. </p>
<p>So we need to ask why we harvest pine forests on such fragile land, and what needs to change to prevent erosion debris and slash being washed from harvested land.</p>
<h2>Pine was a solution</h2>
<p>Ironically, most of these pine forests were planted as a solution to soil erosion that had resulted from the clearing of native forests to create hill country pastoral farms. </p>
<p>The clearing of native forests happened in the 19th and early 20th centuries, but the consequences – erosion, flooding and floodplains covered in silt and rocks – only became apparent decades later. </p>
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<a href="https://theconversation.com/things-fall-apart-why-do-the-ecosystems-we-depend-on-collapse-71491">Things fall apart: why do the ecosystems we depend on collapse?</a>
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<p>Research has shown that pastoral farming on our most erosion-susceptible soils is not sustainable. The productivity of the land is being <a href="http://tur-www1.massey.ac.nz/%7Eflrc/workshops/11/Manuscripts/Rosser_2011.pdf">degraded by loss of soil</a> and large areas have been buried with <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1096-9837(199805)23:5%3C405::AID-ESP854%3E3.0.CO;2-X">sediment eroded from hill country farms upstream</a>. </p>
<p>So the need to reforest large areas of erosion-prone farmland is scientifically well accepted.</p>
<h2>Why pine?</h2>
<p>But why did we choose radiata pine for our reforestation efforts instead of other tree species? </p>
<p>Even today, it is hard to find affordable and feasible alternatives to radiata pine. Affordable is the key word here. We are not a rich country and our liking for “Number 8 wire” solutions makes a virtue out of necessity – we don’t have the money to pay for anything fancier. </p>
<p>Radiata pine is a cheap and easy tree to establish and it grows fast and reliably. Planting native or other exotic trees, such as redwoods, is possible, but it costs more and needs more skill and care to grow a good crop.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1625608210379051008"}"></div></p>
<p>The problem with radiata pine is that if grown as a commercial crop, it is clear-fell harvested after about 28 years. </p>
<p>The clear-felled land is just as erosion-prone as it was before trees were planted – with the added threat of large amounts of logging slash now mixed in with the erosion debris. </p>
<p>It can take six years or more after harvesting before the replanted pine trees cover the ground and once again provide protection to the soil.</p>
<h2>Benefits of pine come with a cost</h2>
<p>If we take a long-term perspective, research shows that even a radiata pine forest that is clear-felled once every 28 years will still <a href="https://www.sciencedirect.com/science/article/pii/S0169555X14004152">significantly reduce erosion</a>, <a href="https://www.nrc.govt.nz/media/hcgft3fi/pakuratahitamingimingilandusestudyreportchapter5hawkesbayrc.pdf">compared with a pastoral farm</a> on erosion-prone hill country. </p>
<p>This is because the erosion from the clear-felled forest is outweighed by the reduced erosion once the replanted trees cover the land. </p>
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<a href="https://theconversation.com/rewilding-isnt-about-nostalgia-exciting-new-worlds-are-possible-44854">Rewilding isn't about nostalgia – exciting new worlds are possible</a>
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<p>However, this is not much comfort to communities in the path of the flood-borne soil and logs from that clear-felled forest. It’s difficult to take a long-term perspective when your backyards and beaches are covered with tonnes of wood and soil. </p>
<h2>Slash a byproduct of efficiency</h2>
<p>Whatever benefits radiata pine forests bring, we need to transition forest management away from “business as usual” clear-felling on erosion-prone hill country.</p>
<p>This transition is possible, but one important problem is not often discussed. The pine forests are privately owned by a range of people including iwi, partnerships made up of mum-and-dad investors and large international forestry companies. </p>
<p>All these people have created or acquired these forests as an investment. </p>
<p>A typical pine forest investment makes <a href="https://nzjforestryscience.nz/index.php/nzjfs/article/view/48/7">a good financial return</a>, but this assumes normal efficient forestry, including clear-felling large areas with highly-productive mechanised logging gangs. </p>
<p>It has become clear that we need to manage forests differently from this large-scale “efficient” model to reduce the risk of erosion and slash from erosion-prone forests. Changing how we manage these forests will inevitably reduce the economic return, and forest investors will absorb this reduction.</p>
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<h2>Time for a permanent fix</h2>
<p>If we go back to when the pine forests being harvested today were planted, the forests had a social value – not just in reducing erosion but in providing employment in rural areas where few jobs were available. </p>
<p>This social value was recognised by government funding, initially through tree planting by a government department, the NZ Forest Service. With the rise of free market economics in the 1980s, such direct government investment was considered inefficient and wasteful. </p>
<p>The Forest Service was disbanded in 1987 and its forests were sold to forestry companies. However, the government continued to promote tree planting on erosion-prone land with subsidies to private investors. </p>
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<p>As these forests grew, they came to be considered purely as business investments and were bought and sold on that basis. When the time came to harvest the trees, the expectation was that these could be clear-fell harvested in the same conventional way as commercial forests growing on land with no erosion risk. </p>
<p>As erosion started occurring on the harvested sites, it became clear why these trees were originally planted as a social investment to protect the land and communities from soil erosion.</p>
<p>Aotearoa New Zealand has achieved control of erosion with a Number 8 wire solution- encouraging private investors to grow commercial pine forests on erosion-prone land. The problem with Number 8 wire solutions is that after a while the wire fails, and you have to find a permanent fix. </p>
<p>Conventional commercial pine forestry was a good temporary solution, but now we need to find a more sustainable way to grow forests on our most erosion-prone lands – and it won’t be as cheap.</p><img src="https://counter.theconversation.com/content/200059/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Bloomberg receives funding for his research on forestry and landslides from the government's Envirolink fund and from local authorities and forestry companies. He is a member of the NZ Institute of Forestry, the NZ Association of Resource Management, and the NZ Society of Soil Science. </span></em></p>Radiata pine was originally a solution to land erosion – but this Number-8 wire fix is past its due date and the forestry industry will likely wear the cost of change.Mark Bloomberg, Adjunct Senior Fellow Te Kura Ngahere – New Zealand School of Forestry, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1956472022-12-08T01:07:09Z2022-12-08T01:07:09ZRepairing gullies: the quickest way to improve Great Barrier Reef water quality<figure><img src="https://images.theconversation.com/files/499526/original/file-20221207-24-jpxu0y.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">James Daley </span>, <span class="license">Author provided</span></span></figcaption></figure><p>Back-to-back <a href="https://theconversation.com/5-major-heatwaves-in-30-years-have-turned-the-great-barrier-reef-into-a-bleached-checkerboard-170719">bleaching events</a> have highlighted the critical threat that climate change poses to the Great Barrier Reef. But few people are aware of the network of gullies pumping out <a href="https://doi.org/10.1016/j.marpolbul.2021.112163">about half</a> the sediment that is polluting reef water quality and threatening its <a href="https://theconversation.com/we-all-know-the-great-barrier-reef-is-in-danger-the-un-has-just-confirmed-it-again-195551">World Heritage status</a>. </p>
<p>These gully networks are like miniature Grand Canyons, some with walls up to 20 metres high. They make a spectacular sight but are a disaster for the land, the reef and the rivers that connect them. </p>
<p>In the UNESCO delegation’s latest <a href="https://whc.unesco.org/document/197090">report</a> on the reef, dramatically scaling up gully repair efforts is the top recommendation. </p>
<p>Along with global warming, degraded water quality is a key threat to the reef. But as the world continues to debate how to combat climate change, the report recognises that fixing gullies will give the reef a fighting chance to survive warming oceans. This is something Australia can do right now.</p>
<p>Over more than a century, <a href="https://doi.org/10.1016/j.marpolbul.2021.112193">land use changes</a> have disturbed fragile soils in grazing country. The unearthed fine sediment from below the surface dissolves like a Berocca tablet when it rains, creating a <a href="https://doi.org/10.1002/esp.5291">gully</a>. Left alone, this process will continue for hundreds of years and keep eating into the landscape. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499287/original/file-20221206-16-nobs2a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Gullies can expose hectares of soil to severe erosion which feeds sediment directly into waterways.</span>
<span class="attribution"><span class="source">James Daley</span></span>
</figcaption>
</figure>
<p>Our team at <a href="https://www.griffith.edu.au/coastal-marine-research-centre/our-research/coastal-processes-management/precision-erosion-sediment-management">Griffith university</a> have been researching gullies since 2005. Over the last decade we’ve <a href="https://nesptropical.edu.au/index.php/round-5-projects/project-5-10/">developed the tools</a> to identify and target the highest priority gullies, and helped design ways to fix them. </p>
<p>Through detailed mapping we’ve found we can identify and target just a few percent of the tens of thousands of gullies to achieve a massive, cost-effective water quality improvement. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-major-heatwaves-in-30-years-have-turned-the-great-barrier-reef-into-a-bleached-checkerboard-170719">5 major heatwaves in 30 years have turned the Great Barrier Reef into a bleached checkerboard</a>
</strong>
</em>
</p>
<hr>
<h2>More than 400,000 dump trucks of sediment a year</h2>
<p>As the planet warms, Australia is already experiencing record heat. For our team working in Queensland’s gullies, temperatures can reach over 50°C in the midday sun. </p>
<p>Field work in these conditions usually feels about as comfortable as working on the surface of Mars. Nonetheless, our team of scientists keep returning because of the staggering implications of the data we’ve been collecting. </p>
<p>Each wet season, the exposed soils in these gullies turn to a yoghurt-like consistency. Their chemistry primes them to readily erode, which they do with every raindrop that <a href="https://doi.org/10.1016/j.catena.2022.106760">falls on them</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/lR0uOHA7f8w?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The eureka moment that could help save the reef.</span></figcaption>
</figure>
<p>In fact, an individual gully can produce <a href="https://www.abc.net.au/news/2015-11-23/unsoiling-the-great-barrier-reef/6963598">thousands of tonnes of fine sediment</a> each year from just a few hectares of land. If you look at the total flow of sediment from all gullies, on average over 400,000 truckloads are dumped across the reef every year, mostly within the inner lagoon.</p>
<p>As sediment and nutrients travel freely down the rivers, they pollute fragile ecosystems, filling water holes, clouding the water and reducing biodiversity. Once they reach the reef lagoon, they smother corals and seagrasses, which struggle to survive.</p>
<p>As the UNESCO report identifies, degraded water quality severely affects the resilience of the reef, limiting its ability to recover from bleaching and cyclones, and to withstand the changes caused by global warming. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-all-know-the-great-barrier-reef-is-in-danger-the-un-has-just-confirmed-it-again-195551">We all know the Great Barrier Reef is in danger – the UN has just confirmed it. Again</a>
</strong>
</em>
</p>
<hr>
<h2>The most effective solution for improving water quality</h2>
<p>Stabilising gullied landscapes requires an approach akin to <a href="https://www.youtube.com/watch?v=L1WBR_VTpmM">mine site rehabilitation</a>. In 2016, we demonstrated that if you reshape (with major earthworks), recap (with rock, soil and mulch) and revegetate the gullies, you can <a href="https://nesptropical.edu.au/index.php/round-3-projects/project-3-1-7/">rapidly repair</a> them. Our research has shown that erosion from priority gullies can be reduced by <a href="https://nesptropical.edu.au/wp-content/uploads/2021/02/NESP-TWQ-Project-3.1.7-Final-Report.pdf">98% within a space of one to two years</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498847/original/file-20221205-19-uud054.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Most gullies have eroded over the last 160 years due to land use changes and fragile soils.</span>
<span class="attribution"><span class="source">Justin Stout</span></span>
</figcaption>
</figure>
<p>We’ve now mapped more than 25,000 individual gullies in three hot spot areas in the Normanby, Burdekin and Fitzroy River catchments. </p>
<p>Remarkably, we <a href="https://nesptropical.edu.au/index.php/round-5-projects/project-5-10/">discovered</a> that only a small proportion of the mapped gullies in each area are contributing a large proportion of the sediment pollution.</p>
<p>For example, in the Burdekin hot spot, we found only about 2% of the gullies contribute 30% of the sediment load to the reef. Targeting these gullies provides the best and quickest way to improve the reef’s water quality.</p>
<p>But the number of gullies repaired to date is a drop in the ocean compared to what still needs to be done.</p>
<p>So far, our method of identifying priority gullies for repair has been implemented across only 1% of the 44-million-hectare reef catchment. The urgent task, as the UNESCO report notes, is to identify other hot spot areas and rapidly roll out the prioritisation mapping to enable targeted remediation to get under way. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=359&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=359&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=359&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=451&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=451&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499288/original/file-20221206-22-6m77fv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=451&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Gullies can be remediated back to healthy landscapes in less than two years.</span>
<span class="attribution"><span class="source">James Daley</span></span>
</figcaption>
</figure>
<h2>What needs to happen now</h2>
<p>UNESCO highlights the critical need to speed up effective action, recommending:</p>
<blockquote>
<p>there is a need to secure a greater reduction of [sediment and nutrient] pollutants in the next three years than has been achieved since 2009. </p>
</blockquote>
<p>The good news is the research has already been done. The data demonstrates it is possible to achieve this ambitious goal. The implementation of on-ground gully repair works with economies of scale is the quickest and most cost-effective way to do it.</p>
<p>Since 2008, Australian governments have set <a href="https://www.reefplan.qld.gov.au/water-quality-and-the-reef/the-plan">sediment reduction targets</a> and invested considerable funds to improve reef water quality. The federal government intends to spend an additional <a href="https://www.dcceew.gov.au/parks-heritage/great-barrier-reef/billion-dollar-reef-protection-package/accelerating-actions">A$580 million</a> over nine years, and a further <a href="https://statements.qld.gov.au/statements/96689">$270 million</a> has been committed by the Queensland government.</p>
<p>Importantly, rapid progress can be made given the current funds earmarked for reef water quality. There are also proven working relationships already in place between our Griffith team, <a href="https://www.youtube.com/watch?v=L1WBR_VTpmM">Traditional Owners </a>, government and <a href="https://ldc.nqdrytropics.com.au/griffith-uni-about/">other stakeholders</a>.</p>
<p>The challenge ahead is delivery. The next step requires a coordinated program to develop a pipeline of targeted gully projects. </p>
<p>The pieces of the puzzle are now all in place and there is no reason for delay.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-tourism-really-suffer-at-sites-listed-as-world-heritage-in-danger-60697">Does tourism really suffer at sites listed as World Heritage In Danger?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/195647/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Brooks has received funding from the Australian Government's National Environmental Science Program (NESP) program and the Great Barrier Reef Foundation's Innovation Program. He also consults to The Palladium Group providing technical advice related to the establishment and implementation of Reef Credits . </span></em></p><p class="fine-print"><em><span>James Daley receives funding from the Australian Government's National Environmental Science Program (NESP) program and the Great Barrier Reef Foundation's Innovation Program.</span></em></p>UNESCO report highlights what needs to be done to save the global icon. But you might be surprised by its top recommendation.Andrew Brooks, Principal Research Fellow - Fluvial Geomorphologist - specialising in catchment erosion research, Griffith UniversityJames Daley, Research Fellow, Coastal and Marine Research Centre, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1944922022-11-23T13:18:18Z2022-11-23T13:18:18ZDreaming of beachfront real estate? Much of Florida’s coast is at risk of storm erosion that can cause homes to collapse, as Daytona just saw<figure><img src="https://images.theconversation.com/files/496325/original/file-20221120-14-dqpu65.jpg?ixlib=rb-1.1.0&rect=0%2C13%2C3000%2C1980&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dozens of homes were left unstable in the Daytona Beach area after Hurricane Nicole's erosion.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/people-look-on-at-homes-that-are-partially-toppled-onto-the-news-photo/1440607558">Joe Raedle/Getty Images</a></span></figcaption></figure><p>Back-to-back hurricanes left an unnerving scene on the Florida coast in November 2022: Several houses, and even swimming pools, were left dangling over the ocean as waves eroded the property beneath them. <a href="https://www.facebook.com/VolusiaCountyEmergencyManagement/posts/pfbid02EZ9SbTjdQhrkGtFm452UhzhzjprPu6h6WaQbPLuMLsRNpCLAuPoPKTZDUvjygUb7l">Dozens of homes and condo buildings</a> in the Daytona Beach area were deemed unsafe. </p>
<p>The destruction has raised a disturbing question: How much property along the rest of the Florida coast is at risk of collapse, and can it be saved?</p>
<p>As the director of <a href="https://dcp.ufl.edu/iadapt/">iAdapt</a>, the International Center for Adaptation Planning and Design at the University of Florida, <a href="https://scholar.google.com/citations?user=ngiXpvgAAAAJ&hl=en">I have been</a> studying climate adaptation issues for the last two decades to help answer these questions.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/h6Fvx6Cw4tE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Drone footage shows homes close to collapsing into the ocean. WPLG/YouTube.</span></figcaption>
</figure>
<h2>Rising seas, aging buildings</h2>
<p>Living by the sea has a strong appeal in Florida – beautiful beaches, ocean views, and often pleasant breezes. However, there are also risks, and they are exacerbated by climate change.</p>
<p>Sea level is forecast to rise on average <a href="https://oceanservice.noaa.gov/hazards/sealevelrise/sealevelrise-tech-report.html">10 to 14 inches</a> (25-35 cm) on the U.S. East Coast over the next 30 years, and 14 to 18 inches (35-45 cm) on the Gulf Coast, <a href="https://theconversation.com/ipcc-climate-report-profound-changes-are-underway-in-earths-oceans-and-ice-a-lead-author-explains-what-the-warnings-mean-165588">as the planet warms</a>. Rising temperatures are also <a href="https://climate.nasa.gov/news/3184/a-force-of-nature-hurricanes-in-a-changing-climate/">increasing the intensity</a> of hurricanes.</p>
<p>With higher seas and larger storm surges, ocean waves more easily erode beaches, weaken sea walls, and submerge cement foundations in corrosive salt water. Together with <a href="https://geodata.dep.state.fl.us/datasets/194ac159bd1e4be294b14dd882d42dcf_0/about">subsidence</a>, or sinking land, they make coastal living riskier.</p>
<figure class="align-center ">
<img alt="Map showing red lines along most of Florida's coast, except at wetlands areas and at the bend toward the Panhandle." src="https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=575&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=575&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=575&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=722&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=722&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496253/original/file-20221119-9310-8cyf0g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=722&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Florida’s erosion risk map shows most of the state’s coastline at critical risk.</span>
<span class="attribution"><a class="source" href="https://geodata.dep.state.fl.us/datasets/FDEP::coastal-critical-erosion-areas/about">Florida Department of Environmental Protection</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The risk of erosion varies depending on the soil, geology and natural shoreline changes. But it is widespread in U.S. coastal areas, <a href="https://geodata.dep.state.fl.us/datasets/FDEP::coastal-critical-erosion-areas/about">particularly Florida</a>. Maps produced by engineers at the <a href="https://geodata.dep.state.fl.us/datasets/FDEP::coastal-critical-erosion-areas/about">Florida Department of Environmental Protection</a> show most of Florida’s coast faces critical erosion risk.</p>
<p>Aging or poorly maintained buildings and sea walls, and older or poor construction methods and materials, can dramatically <a href="https://www.nationalgeographic.com/environment/article/sinking-land-rising-seas-dual-crises-facing-coastal-communities">aggravate the risk</a>.</p>
<h2>Designing better building codes</h2>
<p>So, what can be done to minimize the damage?</p>
<p>The first step is to build sturdier buildings and fortify existing ones according to advanced building codes.</p>
<p>Building codes change over time as risks rise and construction techniques and materials improve. For example, design criteria in the <a href="https://codes.iccsafe.org/content/FLBC2020P1">Florida Building Code</a> for South Florida changed from requiring some new buildings to be able to withstand 146 mph sustained winds in 2002 to 195 mph winds in 2021, meaning a powerful Category 5 hurricane.</p>
<p>The town of <a href="https://www.washingtonpost.com/climate-solutions/2022/10/01/punta-gorda-hurricane-ian-damage/">Punta Gorda</a>, near where Hurricane Ian made landfall in October 2022, showed how homes constructed to the latest building codes have a much better chance of survival.</p>
<p>Many of Punta Gorda’s buildings had been rebuilt after Hurricane Charley in 2004, shortly after the state updated the Florida Building Code. When Ian hit, they survived with less damage than those in neighboring towns. The updated code required new construction to be able to withstand hurricane-force winds, including having shutters or impact-resistant window glass.</p>
<figure class="align-center ">
<img alt="A man clears palm branches from a yard with fallen palm trees in the background, but house standing with no visible damage." src="https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496870/original/file-20221122-21-motmg7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Many homes in Punta Gorda fared better in Hurricane Ian’s winds because they had been rebuilt to higher standards after Hurricane Charley in 2002.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/man-cleans-up-debris-in-the-aftermath-of-hurricane-ian-in-news-photo/1243602882?phrase=punta%20gorda&adppopup=true">Bryan R. Smith / AFP</a></span>
</figcaption>
</figure>
<p>However, even homes built to the latest codes can be vulnerable, because the codes don’t adequately address the environment that buildings sit on. A modern building in a low-lying coastal area could face damage in the future as sea level rises and the shoreline erodes, even if it meets the current flood zone elevation standards.</p>
<p>This is the problem coastal residents faced during Hurricanes Nicole <a href="https://www.latimes.com/world-nation/story/2022-10-06/apocalypse-in-paradise-after-hurricane-ian-a-low-lying-florida-city-contends-with-rising-water">and Ian</a>. Flooding and erosion, exacerbated by sea-level rise, caused the most damage – not wind. </p>
<p>The dozens of beach houses and condo buildings that <a href="https://www.usnews.com/news/us/articles/2022-11-14/florida-county-puts-damage-from-nicole-at-481-million">became unstable or collapsed</a> in Volusia County during Hurricane Nicole might have seemed fine originally. But as the climate changes, the coastal environment changes, too, and one hurricane could render the building vulnerable. Hurricane Ian damaged sea walls in Volusia County, and some <a href="https://www.news-journalonline.com/story/news/2022/11/10/tropical-storm-nicoles-fury-washes-away-homes-wilbur-sea/8323351001/">couldn’t be repaired before Nicole</a> struck. </p>
<h2>How to minimize the risk</h2>
<p>The damage in the Daytona area in 2022 and the <a href="https://miamisao.com/wp-content/uploads/2021/12/GRAND-JURY_202112151434-1.pdf">deadly collapse</a> a year earlier of a condo tower in Surfside should be a wake-up call for all coastal communities.</p>
<p><a href="https://coast.noaa.gov/digitalcoast/topics/vulnerability-assessments.html">Data and tools</a> can show where coastal areas are most vulnerable. What is lacking are policies and enforcement.</p>
<p>Florida recently began requiring that state-financed constructors conduct <a href="https://floridadep.gov/rcp/florida-resilient-coastlines-program/content/resilience-and-coastal-protection-rules-development">a sea-level impact study</a> before starting construction of a coastal structure. I believe it’s time to apply this new rule to any new construction, regardless of the funding source.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tall condo building with balconies and erosion almost to the edge of the building" src="https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496327/original/file-20221120-21-vgk04k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">With Hurricane Nicole’s storm surge coinciding with high tide, the waves breached a condo tower’s sea walls in Daytona Beach in November 2022.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/in-this-aerial-view-seawalls-along-condo-buildings-are-news-photo/1440619402">Joe Raedle/Getty Images</a></span>
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<p>A comprehensive sea-level impact study requirement should also allow for risk-based enforcement, including barring construction in high-risk areas.</p>
<p>Similarly, vulnerability audits – particularly for multistory buildings built before 2002 – can check the integrity of an existing structure and help spot new environmental risks from sea-level rise and beach erosion. Before 2002, the building standard was low and enforcement was lacking, so many of the materials and the structures used in those buildings aren’t up to the standards of today. </p>
<h2>What property owners can do</h2>
<p>There is a range of <a href="https://www.fema.gov/sites/default/files/documents/fema_protect-your-home-from-flooding-brochure_2020.pdf">techniques</a> homeowners can use to fortify homes from flood risks.</p>
<p>In some places, that may mean <a href="https://cpo.noaa.gov/News/ArtMID/7875/ArticleID/2059/Elevating-Houses-Can-Protect-Against-Damaging-Floods-But-How-High-is-High-Enough">elevating the house</a> or improving the lot grading so surface water runs away from the building. Installing a sump pump and remodeling with storm-resistant building materials can help.</p>
<p><a href="https://www.fema.gov/sites/default/files/documents/fema_protect-your-home-from-flooding-brochure_2020.pdf">FEMA</a> suggests other measures to protect against coastal erosion, such as replenishing beach sand, strengthening sea walls and anchoring the home. Engineering can help communities, temporarily at least, through sea walls, ponds and increased drainage. But in the long term, communities will have to assess the vulnerability of coastal areas. Sometimes the answer is <a href="https://theconversation.com/managed-retreat-done-right-can-reinvent-cities-so-theyre-better-for-everyone-and-avoid-harm-from-flooding-heat-and-fires-163052">to relocate</a>.</p>
<p>However, there’s a disturbing trend after hurricanes, and we’re seeing it with Ian: Many damaged areas see lots of money pouring in to rebuild in the same vulnerable locations. An important question communities should be asking is, if these are already in high-risk areas, why rebuild in the same place?</p><img src="https://counter.theconversation.com/content/194492/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Zhong-Ren Peng receives funding from National Science Foundation, Florida Sea Grant, and Florida Department of Transportation. </span></em></p>Dozens of homes near Daytona Beach collapsed or were left unstable when Hurricane Nicole struck. Here’s what can be done to reduce that kind of risk.Zhong-Ren Peng, Professor of Urban and Regional Planning, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1919412022-10-07T04:26:32Z2022-10-07T04:26:32ZThe wild weather of La Niña could wipe out vast stretches of Australia’s beaches and sand dunes<p>Australians along the east cost are bracing for yet another round of heavy rainfall this weekend, after a band of stormy weather soaked <a href="https://theconversation.com/on-our-wettest-days-stormclouds-can-dump-30-trillion-litres-of-water-across-australia-191949">most of the continent</a> this week. </p>
<p>The Bureau of Meteorology has <a href="https://www.youtube.com/watch?v=QUsNQ_-fNbM&ab_channel=BureauofMeteorology">alerted</a> southern inland Queensland, eastern New South Wales, Victoria and northern Tasmania to ongoing flood risks, as the rain falls on already flooded or saturated catchments. </p>
<p>This widespread wet weather heralds <a href="https://theconversation.com/la-nina-3-years-in-a-row-a-climate-scientist-on-what-flood-weary-australians-can-expect-this-summer-190542">Australia’s rare third</a> back-to-back La Niña, which goes hand-in-hand with heavy rain. There is, however, another pressing issue arising from La Niña events: coastal erosion.</p>
<p>The wild weather associated with La Niña will drive more erosion along Australia’s east coast – enough to wipe out entire stretches of beaches and dunes, if all factors align. So, it’s important we heed lessons from past storms and plan ahead, as climate change <a href="https://theconversation.com/2022s-supercharged-summer-of-climate-extremes-how-global-warming-and-la-nina-fueled-disasters-on-top-of-disasters-190546">will only exacerbate</a> future coastal disasters.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/QUsNQ_-fNbM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Ongoing flood risk for eastern Australia |
Bureau of Meteorology.</span></figcaption>
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<h2>How La Niña batters coastlines</h2>
<p>La Niña is associated with warmer waters in the western Pacific Ocean, which increase storminess off Australia’s east coast. Chances of a higher number of tropical cyclones increase, as do the chances of cyclones travelling further south and further inland, and of more frequent passages of east coast lows.</p>
<p>Australians had a taste of this in 1967, when the Gold Coast was hit by the largest storm cluster on record, made up of four cyclones and three east coast lows within six months. 1967 wasn’t even an official La Niña year, with the index just below the La Niña threshold.</p>
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Read more:
<a href="https://theconversation.com/la-nina-3-years-in-a-row-a-climate-scientist-on-what-flood-weary-australians-can-expect-this-summer-190542">La Niña, 3 years in a row: a climate scientist on what flood-weary Australians can expect this summer</a>
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<p>Such frequency didn’t allow beaches to recover between storms, and the overall erosion was unprecedented. It <a href="https://impact.griffith.edu.au/seawall-engineering/">forced many</a> local residents to use anything on hand, even cars, to protect their properties and other infrastructure.</p>
<p>Official La Niña events occurred soon after. This included a double-dip La Niña between 1970 and 1972, followed by a triple-dip La Niña between 1973 and 1976. </p>
<p>These events fuelled two cyclones in 1972, two in 1974 and one in 1976, wreaking havoc along the entire east coast of Australia. Indeed, 1967 and 1974 are considered <a href="https://www.dailytelegraph.com.au/newslocal/northern-beaches/one-of-the-storms-that-hit-us-in-1974-was-among-the-three-worst-since-white-settlement/news-story/0cd5ca874d6b37206762d8485e4eb442">record years</a> for storm-induced coastal erosion.</p>
<p>Studies show the extreme erosion of 1974 was caused by a combination of large waves coinciding with <a href="https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1066&context=scipapers">above-average high tides</a>. It took over ten years for the sand to come back to the beach and for <a href="https://www.jstor.org/stable/4300263">dunes to recover</a>. However, <a href="https://www.nature.com/articles/s43247-022-00437-2">recent studies</a> also show single extreme storms can bring back considerable amounts of sand from deeper waters.</p>
<p>La Niña also modifies the direction of waves along the east coast, resulting in waves approaching from a more easterly direction (<a href="https://www.surfline.com/surf-news/forecaster-blog-la-nina-conditions-mean-surf/97904">anticlockwise</a>). </p>
<p>This subtle change has huge implications when it comes to erosion of otherwise more sheltered <a href="https://au.news.yahoo.com/how-la-nina-may-damage-queensland-tourist-hot-spots-041805874.html">north-facing beaches</a>. We saw this during the recent, and relatively weaker, double La Niña of 2016-18. </p>
<p>In 2016, an east coast low of only moderate intensity produced extreme erosion, similar to that of 1974. Scenes of destruction along NSW – including a collapsed backyard pool on <a href="https://www.wrl.unsw.edu.au/news/wrl-coastal-engineers-document-the-worst-erosion-at-collaroy-since-1974">Collaroy Beach</a> – are now <a href="https://www.abc.net.au/news/2016-06-06/nsw-weather-large-waves-hit-collaroy-coast/7479846#:%7E:text=NSW%20weather%3A%20Collaroy%20swimming%20pool%20collapses%20as%20giant%20waves%20hit%20beachfront%20houses,-Posted%20Sun%205&text=Waves%20up%20to%208%20metres,as%20wild%20weather%20battered%20NSW.">iconic</a>. </p>
<p><a href="https://www.nature.com/articles/s41598-017-05792-1">This is largely</a> because wave direction deviated from the average by 45 degrees anticlockwise, during winter solstice spring tides when water levels are higher. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/2022s-supercharged-summer-of-climate-extremes-how-global-warming-and-la-nina-fueled-disasters-on-top-of-disasters-190546">2022's supercharged summer of climate extremes: How global warming and La Niña fueled disasters on top of disasters</a>
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<h2>All ducks aligned?</h2>
<p>The current triple-dip La Niña started in 2020. Based on Australia’s limited record since 1900, we know the final events in such sequences tend to be the weakest. </p>
<p>However, when it comes to coastal hazards, history tells us smaller but more frequent storms can cause as much or more erosion than one large event. This is mostly about the combination of storm direction, sequencing and high water levels.</p>
<p>For example, Bribie Island in Queensland was hit by relatively large easterly waves from ex-Tropical Cyclone Seth earlier this year, coinciding with above-average high tides. This caused the island to <a href="https://www.abc.net.au/news/2022-01-27/bribie-island-changes-could-create-new-caloundra-bar/100777038#:%7E:text=Ex%2DTropical%20Cyclone%20Seth%20has,splitting%20the%20island%20in%20two.">split in two</a> and form a 300-metre wide passage of seawater. </p>
<p>Further, the prolonged period of easterly waves since 2020 has already taken a toll on beaches and dunes in Australia. </p>
<p>Traditionally, spring is the season when sand is transported onshore under fair-weather waves, building back wide beaches and tall dunes nearest to the sea. However, beaches haven’t had time to fully recover from the previous two years, which makes them more vulnerable to future erosion.</p>
<p>Repeated <a href="https://www.usc.edu.au/about/structure/schools/school-of-science-technology-and-engineering/coast4d">elevation measurements</a> by our team and citizen scientists along beaches in the Sunshine Coast and Noosa show shorelines have eroded more than 10m landwards since the beginning of this year. As the photo below shows, 2-3m high erosion scarps (which look like small cliffs) have formed along dunes due to frequent heavy rainfalls and waves.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488701/original/file-20221007-18-mmjydr.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Dune scarps at a beach in Noosa.</span>
<span class="attribution"><span class="source">Javier Leon</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>On the other hand, we can also see that the wet weather has led to greater growth of vegetation on dunes, such as native spinifex and dune bean.</p>
<p>Experiments in laboratory settings show dune vegetation can dissipate up to 40-50% of the water level reached as a result of waves, and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0272771418307583">reduce erosion</a>. But whether this increase in dune vegetation mitigates further erosion remains to be seen.</p>
<h2>A challenging future</h2>
<p>The chances of witnessing coastal hazards similar to those in 1967 or 1974 in the coming season are real and, in the unfortunate case they materialise, we should be ready to act. Councils and communities need to prepare ahead and work together towards recovery if disaster strikes using, for example, sand nourishment and sandbags.</p>
<p>Looking ahead, it remains essential to further our understanding about coastal dynamics – especially in a <a href="https://www.abc.net.au/news/2022-09-03/gold-coast-no-stranger-to-beach-erosion/101381812#:%7E:text=a%20huge%20challenge-,Millions%20spent%20to%20protect%20Gold%20Coast%20beaches%2C%20but,change%20poses%20a%20huge%20challenge&text=In%201967%2C%20Gold%20Coast%20beaches,and%20ruined%20the%20tourist%20season.">changing climate</a> – so we can better manage densely populated coastal regions. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-fuelled-wave-patterns-pose-an-erosion-risk-for-developing-countries-184064">Climate-fuelled wave patterns pose an erosion risk for developing countries</a>
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<p>After all, much of what we know about the dynamics of Australia’s east coast has been supported by coastal monitoring programs, which were implemented <a href="https://www.publications.qld.gov.au/dataset/coastal-observation-program-engineering">along Queensland</a> and NSW after the 1967 and 1974 storms. </p>
<p>Scientists predict that La Niña conditions along the east coast of Australia – such as warmer waters, higher sea levels, stronger waves and more waves coming from the east – will become <a href="https://theconversation.com/climate-fuelled-wave-patterns-pose-an-erosion-risk-for-developing-countries-184064">the norm under climate change</a>. </p>
<p>It’s crucial we start having a serious conversation about coastal adaptation strategies, including implementing a <a href="https://www.usc.edu.au/about/unisc-news/news-archive/2022/january/coastal-erosion-may-force-retreat-from-the-sea#:%7E:text=Giving%20up%20land%20to%20the,of%20the%20Sunshine%20Coast%20researcher.">managed retreat</a>. The longer we take, the higher the costs will be.</p><img src="https://counter.theconversation.com/content/191941/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Javier Leon receives funding from Noosa Council and The Queensland Earth Observation (EO) Hub, a partnership between the Queensland Government and SmartSat Cooperative Research Centre (CRC)</span></em></p>We must heed lessons from past storms and plan ahead, as climate change will only exacerbate future coastal disasters.Javier Leon, Senior lecturer, University of the Sunshine CoastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1877842022-09-21T02:48:54Z2022-09-21T02:48:54ZWe helped fill a major climate change knowledge gap, thanks to 130,000-year-old sediment in Sydney lakes<figure><img src="https://images.theconversation.com/files/482252/original/file-20220901-23-79mmzt.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C2492%2C1641&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lake Couridjah, Thirlmere Lakes National Park in New South Wales</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Plants capture <a href="https://earthobservatory.nasa.gov/features/CarbonCycle">around half</a> the carbon we emit by burning fossil fuels, making them a crucial part of mitigating climate change. But carbon is often released back into the atmosphere when plants die, decompose and eventually turn into dirt.</p>
<p>Carbon is only permanently removed from the atmosphere if it’s stored in sediments that accumulate at the bottom of oceans, lakes, reservoirs, or in peat bogs. </p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0921818122001898">Our latest research</a> on the Thirlmere Lakes near Sydney aimed to find out how trees, shrubs and soils in Australia’s eastern tablelands responded to climate changes over the last 130,000 years. The key question we sought to answer was whether carbon stored in Australia’s trees, shrubs, and soils contribute to the pool of carbon stored safely in lake sediment. </p>
<p>The answer, we determined, depends on a number of crucial factors, and erosion plays an essential, previously neglected, part. </p>
<p>Erosion is like a conveyer belt for carbon – it transports carbon to the lake from nearby hills where plants die. We found when the climate near Sydney was warm and wet, then trees and shrubs flourished and erosion was reduced. So while more carbon was stored in plants, it took longer for carbon in soil to be safely buried in the lake. </p>
<p>Previous research has shown ignoring the impact of erosion on carbon burial has caused Australia to overestimate the amount of <a href="https://www.nature.com/articles/nclimate2829">carbon</a> emitted into the atmosphere over the last 50 years, by a staggering 40%. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/dig-this-a-tiny-echidna-moves-8-trailer-loads-of-soil-a-year-helping-tackle-climate-change-155947">Dig this: a tiny echidna moves 8 trailer-loads of soil a year, helping tackle climate change</a>
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<h2>The cycle of carbon</h2>
<p>Plants capture carbon dioxide from the atmosphere during photosynthesis, and store carbon in their tissue. So what happens when plants die? </p>
<p>The equation is easier for the oceans: dead <a href="https://oceanservice.noaa.gov/facts/phyto.html">phytoplankton</a> (tiny algae floating close to the surface) sinks to seafloor, where most of its captured carbon is stored safely far away from the atmosphere. On land things are more complex.</p>
<p>When trees and shrubs die, they cover the surface, decompose and become part of the soil. In fact, <a href="https://www.sciencedirect.com/science/article/pii/S0012825215300817">80%</a> of carbon on land is stored in soils. Decomposition releases some of the captured carbon back into the atmosphere, unless they’re buried deep. </p>
<p>In Australia, much more carbon is stored when weather conditions are wetter. During the strong La Niña event of 2010-2012, large areas of the Australia’s dry interior and temperate landscape experienced significant “greening”. </p>
<p>Research <a href="https://www.nature.com/articles/srep23113">shows 20%</a> more carbon was captured from the Earth’s atmosphere during this La-Niña event due to increasing plant growth. Australia contributed <a href="https://www.nature.com/articles/nature13376">more than half</a> of this.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482253/original/file-20220901-19-ajx6ox.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Thirlmere Lakes during dry conditions.</span>
<span class="attribution"><span class="source">Timothy J. Cohen</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The last 130,000 years</h2>
<p>The story is even more dramatic if you look back at the last 130,000 years. During this time, the planet experienced cycles of two climate phenomena: glacial periods and interglacial periods. </p>
<p>A “glacial” period is characterised by much colder and drier conditions, when wide parts of northern Europe, Eurasia, and America were covered by ice kilometres thick. The last time it peaked was around 21,000 years ago.</p>
<p>Australia endured warmer and wetter conditions during “interglacial” periods, which peaked around 125,000 years ago and again over the last 11,600 years.</p>
<p>For our research, we drilled deep into Sydney’s Thirlmere Lake mud, and pulled up long columns of sediment containing traces of vegetation, climate, and erosion from the last 130,000 years. We observed significant changes in the types of vegetation growing in the catchment over this time.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/soil-abounds-with-life-and-supports-all-life-above-it-but-australian-soils-need-urgent-repair-187280">Soil abounds with life – and supports all life above it. But Australian soils need urgent repair</a>
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<p>Shrubs and large trees such as eucalypts flourished during warmer and wetter interglacial periods. They were less abundant when it was colder and dry during glacial periods, when grass and herbs became more common.</p>
<p>Large trees <a href="https://besjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2006.01221.x">capture more</a> carbon dioxide from the atmosphere than grasses and herbs. And this captured carbon then accumulates in the surface of soils when the plant dies. </p>
<p>But how is the soil-carbon transported from the slopes where the trees and shrubs grow, to the bottom of the lake?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=294&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=294&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=294&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=370&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=370&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482254/original/file-20220901-809-84vlza.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=370&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Extracting sediment cores from a lake.</span>
<span class="attribution"><span class="source">Fabian Boesl</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Soil erosion</h2>
<p>Erosion – whether gravity, water or wind - forms our landscape and is essential for the accumulation of soil carbon in lakes, reservoirs and the oceans.</p>
<p>The deeper the carbon is buried in the sediments of these reservoirs, the more efficiently it is locked away from the atmosphere. In contrast, the longer it remains on the slopes and in soils close to the surface, the more it decomposes, and carbon dioxide is released back into the atmosphere.</p>
<p>For the wider Sydney region, more plant growth occurred during the interglacial period, which take up vast amounts of carbon dioxide from the atmosphere. But this may be offset by decreased erosion. And indeed, our data suggests decreased erosion during interglacial periods. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/65-000-years-of-food-scraps-found-at-kakadu-tell-a-story-of-resilience-amid-changing-climate-sea-levels-and-vegetation-181240">65,000 years of food scraps found at Kakadu tell a story of resilience amid changing climate, sea levels and vegetation</a>
</strong>
</em>
</p>
<hr>
<p>This decreased erosion is because of the protection of trees which, for example, stabilise the soil with their roots. Indeed, we found tree cover slows the rate that soil carbon moves from slope to lake by nearly 10 times. </p>
<p>This means there’s much more time for soils to decompose on the slope, and to release carbon back into the atmosphere.</p>
<p>Nevertheless, we still recorded significantly higher carbon storage in lake sediments during warmer and wetter periods, thanks largely to the greater growth of trees and shrubs compared to grasses, which are more abundant during interglacial periods. This compensates for the reduced erosion. </p>
<p>We also found the lake transformed into a productive wetland during warm periods. This means more carbon is also captured by plants growing in the lake.</p>
<h2>What will happen under climate change?</h2>
<p>The interplay between climate, vegetation, and erosion is difficult to quantify. Our research fills a critical gap in knowledge, as climate models currently don’t account for soil-carbon erosion. </p>
<p>Those models assume all soil-carbon is eventually emitted back into the atmosphere, introducing uncertainties into climate predictions. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482255/original/file-20220901-27-wp7dvb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Thirlmere Lakes during wet conditions.</span>
<span class="attribution"><span class="source">Fabian Boesl</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Future climate change may raise the risk of the <a href="https://www.environment.nsw.gov.au/research-and-publications/our-science-and-research/our-research/water/freshwater-and-wetlands/thirlmere-lakes-research">Thirlmere Lakes</a> drying out, which means the sediments will be exposed, which promotes decomposition. This means the previously stored carbon will be emitted back into the atmosphere as carbon dioxide.</p>
<p>Extreme aridity may also reduce terrestrial plant growth, as it did during the millennium drought. </p>
<p>Further, destruction of vegetation by <a href="https://theconversation.com/australian-forests-will-store-less-carbon-as-climate-change-worsens-and-severe-fires-become-more-common-173233">severe bushfires</a> reduce biomass yield to the wetlands. Preserving Australia’s unique native terrestrial vegetation and wetlands is therefore essential to sustain the continent’s role in the global carbon cycle.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australian-forests-will-store-less-carbon-as-climate-change-worsens-and-severe-fires-become-more-common-173233">Australian forests will store less carbon as climate change worsens and severe fires become more common</a>
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</p>
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<img src="https://counter.theconversation.com/content/187784/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The research at the Thirlmere Lakes was funded by the NSW Department of Environment and Heritage and commenced following community concerns that nearby mining was affecting the hydrology of the lakes and the Friends of Thirlmere Community group continues to advocate for the protection and enjoyment of the area. The authors gratefully acknowledge the contributions of Matthew Forbes to this article. We acknowledge the contribution of the Aboriginal people of the area who are the first custodians of Country.
Alexander Francke receives funding from the Australian Research Council.
</span></em></p><p class="fine-print"><em><span>Anthony Dosseto receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Haidee Cadd receives funding from The Australian Research Council.</span></em></p><p class="fine-print"><em><span>Tim Cohen has received funding from the Australian Research Council (ARC); ARC Centre of Excellence Scheme (Project Number CE170100015) and ARC Future Fellowship (FT180100524) and NSW OEH Thirlmere lakes Research Program</span></em></p>80% of carbon on land in stored in soil. Our new research investigated how erosion transports this carbon to the bottom of lakes, where it’ll never be released into the atmosphere.Alexander Francke, Research Fellow, University of AdelaideAnthony Dosseto, Professor, University of WollongongHaidee Cadd, Research associate, University of WollongongTim Cohen, Associate Professor and ARC Future Fellow, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1908982022-09-19T11:45:55Z2022-09-19T11:45:55ZTyphoon Merbok, fueled by unusually warm Pacific Ocean, pounded Alaska’s vulnerable coastal communities at a critical time<figure><img src="https://images.theconversation.com/files/485177/original/file-20220918-52219-igrjib.jpg?ixlib=rb-1.1.0&rect=28%2C7%2C1649%2C1058&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A satellite image shows how vast the remnants of Typhoon Merbok were as the storm hit the Alaska coast.</span> <span class="attribution"><a class="source" href="https://twitter.com/NWSFairbanks/status/1571054643383533569">National Weather Service</a></span></figcaption></figure><p><em>The powerful remnants of Typhoon Merbok pounded Alaska’s western coast on Sept. 17, 2022, pushing homes off their foundations and tearing apart protective berms as water flooded communities.</em> </p>
<p><em>Storms aren’t unusual here, but Merbok built up over unusually warm water. Its <a href="https://twitter.com/NWSOPC/status/1570883906794311682">waves reached 50 feet</a> over the Bering Sea, and its storm surge sent water levels into communities at <a href="https://twitter.com/AlaskaWx/status/1571266836771270659">near record highs</a> along with near hurricane-force winds.</em></p>
<p><em>Merbok also hit during the fall subsistence harvest season, when the region’s Indigenous communities are stocking up food for the winter. Rick Thoman, a <a href="https://news.uaf.edu/expertsguide/rick-thoman/">climate scientist at the University of Alaska Fairbanks</a>, explained why the storm was unusual and the impact it’s having on coastal Alaskans.</em></p>
<h2>What stands out the most about this storm?</h2>
<p>It <a href="https://www.weather.gov/media/arh/RN-05-0003.pdf">isn’t unusual</a> for typhoons to affect some portion of Alaska, typically in the fall, but Merbok was different. </p>
<p>It <a href="https://twitter.com/Climatologist49/status/1571218582293610496/photo/1">formed in a part of the Pacific</a>, far east of Japan, where historically few typhoons form. The water there is typically too cold to support a typhoon, but right now, we have extremely warm water in the north-central Pacific. Merbok traveled right over waters that are the warmest on record going back about 100 years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map shows warm waters off Japan and Russia's Kamchatka region." src="https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485179/original/file-20220918-51705-mljo8r.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sea surface temperatures show unusually warm water over the eastern Pacific Ocean, where Typhoon Merbok passed through.</span>
<span class="attribution"><a class="source" href="https://uaf-accap.org/">Alaska Center for Climate Assessment</a></span>
</figcaption>
</figure>
<p>The Western Bering Sea, closer to Russia, has been running above normal sea surface temperature since last winter. The Eastern Bering Sea – the Alaska part – has been normal to slightly cooler than normal since spring. That temperature difference in the Bering Sea helped to feed the storm and was probably part of the reason the storm intensified to the level it did. </p>
<p>When Merbok moved in to the Bering Sea, it wound up being by far the strongest storm this early in the autumn. We’ve had stronger storms, but they typically occur in October and November.</p>
<h2>Did climate change have a bearing on the storm?</h2>
<p>There’s a strong likelihood that Merbok was able to form where it did because of the <a href="https://www.ncei.noaa.gov/cag/global/time-series/globe/ocean/12/12/1880-2022">warming ocean</a>.</p>
<p>With warm ocean water, there’s <a href="https://climate.nasa.gov/ask-nasa-climate/3143/steamy-relationships-how-atmospheric-water-vapor-amplifies-earths-greenhouse-effect/">more evaporation going in the atmosphere</a>. Because all the atmospheric ingredients came together, Merbok was able to bring that very warm moist air along with it. Had the ocean been a <a href="https://www.ncei.noaa.gov/cag/global/time-series/globe/ocean/12/12/1880-2022">temperature more typical of 1960</a>, there wouldn’t have been as much moisture in the storm.</p>
<figure class="align-center ">
<img alt="Bar chart showing temperatures rising" src="https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=453&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=453&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485199/original/file-20220919-62263-2t01r9.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=453&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Global ocean temperatures have been rising. The bars show how annual temperatures departed from the 20th century average.</span>
<span class="attribution"><a class="source" href="https://www.ncei.noaa.gov/cag/global/time-series/globe/ocean/12/12/1880-2022">NOAA</a></span>
</figcaption>
</figure>
<h2>How extreme was the flooding compared to past storms?</h2>
<p>The most outstanding feature as far as impact is the tremendous area that was damaged. All coastal regions north of Bristol Bay to just beyond the Bering Strait – hundreds of miles of coastline – had some impact. </p>
<p>At Nome – one of the very few places in western Alaska where we have long-term ocean level information – the ocean was <a href="https://twitter.com/AlaskaWx/status/1571266836771270659">10.5 feet</a> (3.2 meters) above the low-tide line on Sept. 17, 2022. That’s the highest there in nearly half a century, since the historic storm of <a href="https://doi.org/10.1080/00431672.1975.9931740">November 1974</a>.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1571514507041595392"}"></div></p>
<p>In <a href="https://www.nytimes.com/2022/09/17/us/alaska-storm.html">Golovin</a> and <a href="https://www.ktoo.org/2022/09/17/powerful-storm-slams-western-alaska/">Newtok</a>, multiple houses floated off their foundations and are no longer habitable.</p>
<p><a href="https://savingplaces.org/stories/fighting-the-rising-tide-in-shaktoolik-alaska#.Yyd7pHbML8A">Shaktoolik</a> lost its protective berm, which is very bad news. Prior to building the berm, the community’s freshwater supply was easily inundated with saltwater. The community is now at greater risk of flooding, and even a moderate storm could inundate their fresh water supply. They can rebuild it, but how fast is a matter of time and money and resources. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1571310275739156480"}"></div></p>
<p>Another important impact is to hunting and fishing camps along the coasts. Because of the <a href="https://www.nps.gov/gis/storymaps/cascade/v1/index.html?appid=42e0af0fd1ab485596a0475d186a0919">region’s subsistence economy</a>, those camps are crucial, and they are expensive to rebuild. </p>
<p>There are no roads into these coastal communities, and <a href="https://www.ktoo.org/2022/02/21/construction-supply-chain-woes-in-rural-alaska/">getting lumber for rebuilding</a> homes and these camps is difficult. And we’re moving into typically the stormiest time of year, which makes recovery harder and planes often can’t land.</p>
<p>Lots of places also lost power and cell phone communication. The power in these remote areas is generated in the community – if that goes out there is no alternative. People lose power to their freezers, which they’re stocking up for the winter. Towns might have one grocery store, and if that can’t open or loses power, there is no other option. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1571235158342373383"}"></div></p>
<p>Winter is coming, and the time when it’s feasible to make repairs is running short. This is also the middle of hunting season, which in western Alaska is not recreation – it’s how you feed your family. These are almost all predominantly or almost exclusively Indigenous communities. Repairs are going to take time away for subsistence hunters, so all of these things are coming together at once. </p>
<h2>Does the lack of sea ice as a buffer make a difference for erosion?</h2>
<p>Historically, with storms later in the season, even a small bit of sea ice can offer protection to dampen the waves. But there’s <a href="http://nsidc.org/arcticseaicenews/2022/09/the-arctics-bald-spot/">no ice in the Bering Sea</a> at all this time of year. The full wave action pounds right to the beach. </p>
<p>As sea ice <a href="https://climate.nasa.gov/vital-signs/arctic-sea-ice/">declines with warming global temperatures</a>, communities will see more damage from storms later in the year, too.</p>
<h2>Are there lessons from this storm for Alaska?</h2>
<p>As bad as this storm was, and it was very bad, others will be coming. This is a stormy part of the world, and state and federal governments need to do a better job of communicating risks and helping communities and tribes ahead of time. </p>
<p>That might mean evacuating vulnerable people. Because if you wait until it’s certain that there’s a problem, it’s too late. Almost all of these communities are isolated. </p>
<p>I would say this is a classic case of large-scale weather models showing a general idea of the risk far in advance, but it takes longer to respond for isolated communities like those in rural Alaska. By Sept. 12, <a href="https://twitter.com/Climatologist49/status/1571218582293610496">Merbok’s storm track was clear</a>, but if communities aren’t briefed until a day or two days before the storm, there isn’t enough time for them to fully prepare.</p><img src="https://counter.theconversation.com/content/190898/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Thoman does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Most of the flooded communities are Indigenous and rely on subsistence hunting that residents would normally be doing right now. Recovering from the damage will make that harder.Rick Thoman, Alaska Climate Specialist, University of Alaska FairbanksLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1872492022-07-27T16:00:43Z2022-07-27T16:00:43ZWe must rethink the way we build along the St. Lawrence River<figure><img src="https://images.theconversation.com/files/474705/original/file-20220718-68563-2ywvhn.jpg?ixlib=rb-1.1.0&rect=17%2C35%2C5838%2C3952&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Riverbanks are reinforced to reduce flood risks, but these techniques reduce biodiversity and limit public accessibility.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>The St. Lawrence River is immeasurably rich. <a href="https://wwf.ca/stories/5-amazing-facts-about-the-st-lawrence-river/">Draining a quarter of the planet’s freshwater reserves</a>, it forms one of the largest ecosystems in the world.</p>
<p>Since time <a href="https://www.thecanadianencyclopedia.ca/en/article/st-lawrence-river">immemorial, its navigation has played a major role</a> in the cultural, economic and social development of the continent. Today it is the main common heritage landmark of Indigenous people, descendants of the first European settlers and the newcomers inhabiting the region.</p>
<p>However, the <a href="https://journals.openedition.org/vertigo/2986?lang=en">privatization of its shoreline for residential, commercial and industrial purposes</a> — the main driver of urbanization in eastern North America — continues to undermine future generations. Centred on a logic of exploitation that is exclusive to the richest, privatization causes significant ecological disturbance and considerable risk-management costs for the Québec government. <a href="https://www.planstlaurent.qc.ca/en/">Public access to the river is clearly inadequate</a>.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469058/original/file-20220615-9549-jj1phn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
</figcaption>
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<p><em>This article is part of our series, <a href="https://theconversation.com/ca-fr/topics/fleuve-saint-laurent-116908">The St. Lawrence River: In depth</a>.
Don’t miss new articles on this mythical river of remarkable beauty. Our experts look at its fauna, flora and history, and the issues it faces. This series is brought to you by <a href="https://theconversation.com/ca-fr">La Conversation</a>.</em></p>
<hr>
<p>The future of the river is in the hands of all citizens. We need a wide-reaching project that includes all those concerned: national, provincial and municipal governments, the scientific community, civil society, businesses, as well as the local and trans-local communities that live along the river. My colleagues and I have proposed a project, called Fluvialities, that meets the <a href="https://sdgs.un.org/goals/goal15">United Nations Sustainable Development Goals</a>, as well as the principles of human rights and <a href="https://www.un.org/development/desa/indigenouspeoples/declaration-on-the-rights-of-indigenous-peoples.html">Indigenous Peoples’ rights</a>.</p>
<p>Led by a group of researchers and professionals at the Université de Montréal, of which I am a member, the Fluvialities project of the <a href="https://nouvelles.umontreal.ca/en/article/2019/10/25/the-unesco-chair-in-urban-landscape-at-universite-de-montreal-builds-bridges/">UNESCO Chair in Urban Landscape</a> brings together scientific and citizen knowledge to identify and implement concrete actions over the next decade, across the entire St. Lawrence watershed, but focusing more on inhabited areas near the banks of the river.</p>
<p>The project will develop a number of landscape and ecosystem design strategies, which address ecosystem integrity and sustainability. It also aims to re-examine constitutional, legislative and regulatory frameworks, as well as the social norms, that define our collective relationship to this vast expanse of water.</p>
<h2>Flooding and erosion</h2>
<p>In recent years, climate change has increased the risk of flooding along the river and its tributaries, due to rising sea levels and increasing rainfall throughout the river basin. In an effort to reduce flood risks, riverbanks have been reinforced. But the stabilization techniques that protect private land and industrial sites from water level fluctuations reduce biodiversity and limit public accessibility.</p>
<figure class="align-center ">
<img alt="A row of houses along a riverbank" src="https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473652/original/file-20220712-30699-qtvy73.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Riprap stabilization and riverbank protection techniques along the St. Lawrence River reduces the shorlines’ biodiversity.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>If <a href="https://www.ipcc.ch/sr15/">global temperatures continue to increase to 1.5 C or 2 C above pre-industrial levels</a>, sea levels will also rise. Building residential neighbourhoods and industrial sites near shorelines puts many lives at risk from flooding, and <a href="https://www.nature.com/articles/d41586-018-06827-x">could cause billions of dollars in property damage</a>.</p>
<p>All municipalities along the river will be affected, either directly or indirectly, by rising water levels.</p>
<p>In addition, a phenomenal amount of <a href="https://www.cbc.ca/news/canada/nova-scotia/ocean-pollution-seafloor-junk-bay-of-fundy-study-1.5360145">debris and chemicals are spread by the flow, polluting not only the river ecosystem</a>, but also the land and the groundwater in the catchment area. This accelerated process of riverbank erosion threatens a growing number of natural riverine habitats, promoting landslides and the release of toxic substances into the environment.</p>
<p>This is now well known among researchers and policymakers. However, despite <a href="https://www.planstlaurent.qc.ca/en/">excellent work</a> to assess the many risks and propose development strategies to mitigate them, there is currently no project that has a long-term development vision for the entire St. Lawrence River.</p>
<p>It therefore essential that current and future knowledge on natural and human risks be implemented quickly. We must radically rethink our relationship with the St. Lawrence River habitat, from the Great Lakes to the Atlantic Ocean.</p>
<h2>A global trend</h2>
<p>The first project of its kind in the world, Fluvialities, initiated in 2021-22, is part of an <a href="https://living-with-rivers.com/en/">overall trend towards worldwide governance of major rivers</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473651/original/file-20220712-26-jbm29t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">View of Montréal from the South Shore. Like Montrealers, the majority of Québec residents live on the banks of the St. Lawrence River.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>We are inspired by such projects as “<a href="https://archive.arch.ethz.ch/studio-basel/publications/books/switzerland-an-urban-portrait.html">Switzerland: an Urban Portrait</a>”, by Studio Basel, research on the <a href="https://submarinechannel.com/lagos-wide-close/">metropolis of Lagos, Nigeria, led by Dutch architect Rem Koolhaas</a>, the School of the Anthropocene, led by French geographer Michel Lussault, and Italian urban planner Paola Viganò’s <a href="https://www.youtube.com/watch?v=T2GvZAWwew4">vision for a horizontal metropolis</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/T2GvZAWwew4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Italian urbanist Paola Viganò’s vision for a horizontal metropolis.</span></figcaption>
</figure>
<p>These approaches echo a growing practice in the field of urban planning and landscape architecture. By tackling societal challenges on several levels, these disciplines are now generating solutions that benefit society and the environment while promoting economic development. Projects drawn from this knowledge are more likely to reach sustainability goals.</p>
<h2>A multidisciplinary network</h2>
<p>Through 2023-24, Fluvialities will be the subject of an initial consolidation phase. We aim to build a network of university researchers, non-profit organizations, representatives of local communities and companies concerned about the future of the river.</p>
<p>We expect to hold an initial public consultation on citizens’ aspirations in 2024-25. This is inspired by interactive democracy exercises on environmental issues recently <a href="https://www.conventioncitoyennepourleclimat.fr/en/">conducted in France</a> and <a href="https://www.climateassembly.uk">the United Kingdom</a>.</p>
<p>At the same time, we are building a digital atlas of the river’s scientific, social and cultural knowledge. These activities will include university and college teaching activities based on a research-creation approach where students participate in the process.</p>
<p>Educational teams of local and international experts will conduct planning and development workshops on different sections of the river as well as on comparable international contexts.</p>
<p>The sustainable and inclusive development of the St. Lawrence River deserves our attention. If its development continues in its current form, it will have a negative consequences for the people and the environment of North America. We must put in place a transnational strategy for the inclusive and sustainable development of the river and our society.</p><img src="https://counter.theconversation.com/content/187249/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shin Koseki ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>The sustainable and inclusive development of the St. Lawrence River is essential. A prolonged laissez-faire attitude will have harmful consequences on people and the environment.Shin Koseki, UNESCO Chair Professor in Urban Landscape, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1840642022-06-16T19:54:35Z2022-06-16T19:54:35ZClimate-fuelled wave patterns pose an erosion risk for developing countries<figure><img src="https://images.theconversation.com/files/469161/original/file-20220616-13059-tbwu7p.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6377%2C3853&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Durban, South Africa</span> <span class="attribution"><span class="source">Getty</span></span></figcaption></figure><p>The world’s coastlines are at the forefront of climate change. That’s because they’re constantly changing, and respond quickly to changes in climate. They’re particularly important because around <a href="https://www.jstor.org/stable/4299200">70%</a> of the world’s population live within 100km of the coast, and <a href="https://www.oecd.org/ocean/topics/ocean-shipping/">90%</a> of the world’s trade passes through ports on the coast. The global economy relies on our coastal systems functioning because of the volume of trade and commerce that takes place at or through the coastal zone.</p>
<p>Change and disruption do not fall evenly across the globe, however. Our <a href="https://www.nature.com/articles/s41558-022-01389-3">new research</a> is the first to find a group of coastal locations around the world highly vulnerable to one specific climate-driven change: stronger waves, or waves coming from a different direction, which may cause widespread coastal erosion.</p>
<p>These changes will affect major ports and coastal cities such as Lima, Cape Town, Durban and Mombasa, as well as broadly affecting the Pacific-facing east coasts of Peru and Chile, the Atlantic-facing west coasts of Namibia and South Africa, and the southeast coast of Kenya down to South Africa. </p>
<p>Many of these locations are in developing nations with low GDP, making it harder to adapt or reduce damage from these changes. While some areas will be able to respond better than others, the combined GDP of countries most affected is only about one percent of global GDP. This speaks to how climate change can act as an inequality amplifier, hitting the Global South the hardest. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="mombasa and sea" src="https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469162/original/file-20220616-21-vn8qsv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Coastal cities like Mombasa in Kenya may face unexpected coastal erosion from new wave patterns if emissions continue unabated.</span>
<span class="attribution"><span class="source">Getty</span></span>
</figcaption>
</figure>
<h2>What’s the link between climate change and wave strength?</h2>
<p>Our <a href="https://theconversation.com/climate-change-is-making-ocean-waves-more-powerful-threatening-to-erode-many-coastlines-160998">previous work</a> found climate change is already making waves more powerful, particularly in the Southern Hemisphere. </p>
<p>How? <a href="https://theconversation.com/curious-kids-why-are-there-waves-112015">Ocean waves</a> are generated by winds blowing along the ocean surface. If the sea surface becomes warmer, wind patterns change as well. In turn, this can alter the wave conditions across the world’s oceans.</p>
<p>But due to reasons such as the fact that oceans are heating at different rates in different places, wave conditions are not changing at the same rate everywhere. Some areas will be worse affected than others.</p>
<p>Why does this matter for humans on dry land? Because waves have shaped Earth’s coastlines for millions of years. Even small, sustained changes in waves can have long term consequences for our coasts and the people who rely on them. </p>
<p>That’s because waves control how much sand is moved along the coast, and where it is deposited. Changes to local wave climates could dramatically increase erosion in some areas, for instance, threatening human and natural use of the coasts as well as infrastructure and houses.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Waves and beach from above" src="https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=458&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=458&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469113/original/file-20220616-12840-iehxqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=458&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Waves move sand along beaches.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>To find out where they are changing the most, we applied wave tracking algorithms to models of future wave conditions. To model ocean waves in the future, we used <a href="https://en.wikipedia.org/wiki/Wind_wave_model">numerical wave models</a> driven by atmospheric conditions such as wind and air pressure, taken from <a href="https://en.wikipedia.org/wiki/General_circulation_model">global climate models</a> used by the Intergovernmental Panel on Climate Change. </p>
<p>Our work builds on <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093622">years of research</a> developing a method to track different wave conditions (or “wave climates”) globally. For example, the Southern Ocean wave climate is characterised by big, powerful waves with long wave periods as they circumnavigate the globe west to east. </p>
<p>By comparison, the wave climate of equatorial regions is typically lower energy, shorter wave period, and travels west to east. The characteristics of each wave climate is what we call their “signature” and this is what we track. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-is-making-ocean-waves-more-powerful-threatening-to-erode-many-coastlines-160998">Climate change is making ocean waves more powerful, threatening to erode many coastlines</a>
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<p>We use data from the last 19 years to identify the signature for each wave climate, and track how they will change under different emissions scenarios by the end of the century. By comparing the differences between present and future conditions across the world’s oceans, we can identify the areas likely to see the greatest changes in wave conditions.</p>
<h2>What about sea level rise?</h2>
<p>Until recently, most of the focus on coastal climate change impacts has been on <a href="https://theconversation.com/au/topics/sea-level-rise-36469">sea level rise</a>, which will affect low-lying areas and cities. </p>
<p>In the next few decades, however, changes in wave conditions are likely to be more important than sea level rise along millions of kilometres of the world’s sandy coastlines. </p>
<p>By itself, sea level rise does not cause erosion. Waves do. As the sea rises, waves can expand the reach and eat away at the beach and beyond. The net effect of wave power increasing and sea level rise will vary locally, however, because changes in wave conditions can either boost or dampen the effect of sea level rise on the coast, depending on how much sand is available and where it is moved to. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Eroded road near sea" src="https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469112/original/file-20220616-12-8vynqo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Stronger waves coupled with sea level rise will trigger major erosion in some places.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Cutting carbon emissions makes a difference</h2>
<p>Our modelling explored two scenarios. The first was a high emissions future world with little to no carbon emissions reduction, leading to global temperatures rising by over 4°C by the end of the century compared to pre-industrial levels. </p>
<p>The second was a low emissions scenario, where global warming is kept below 2°C by 2100, which requires deep and immediate reduction in global carbon emissions.</p>
<p>We found reducing emissions can have a significant impact on how much wave conditions change in the future. By keeping warming under 2°C, we found there would be almost no change in wave conditions for many of the coastal locations which we identified as particularly at risk in a 4°C world. </p>
<p>It is still not too late to avoid the worst impacts of climate change, but the window of opportunity is closing fast. We hope this research will help direct funding for coastal adaptation and resilience to the areas which will need it most.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-may-change-the-way-ocean-waves-impact-50-of-the-worlds-coastlines-121239">Climate change may change the way ocean waves impact 50% of the world’s coastlines</a>
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<img src="https://counter.theconversation.com/content/184064/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Mortlock is affiliated with Aon, Australia.</span></em></p><p class="fine-print"><em><span>Adrean Webb receives funding from Japan Society for the Promotion of Science and Ministry of Education, Culture, Sports, Science and Technology, Japan. </span></em></p><p class="fine-print"><em><span>Itxaso Odériz received funding from JSPS KAKENHI (19K15099, 19H00782), Integrated Research Program for Advancing Climate Models (TOUGOU Program: JPMXD0717935498) supported by MEXT of Japan, and from CEMIE-Océano, CONACYT-SENER Sustentabilidad Energética project.</span></em></p><p class="fine-print"><em><span>Nobuhito Mori receives funding from JSPS KAKENHI (19K15099, 19H00782) and Integrated Research Program for Advancing Climate Models (TOUGOU Program: JPMXD0717935498) supported by MEXT of Japan.
</span></em></p><p class="fine-print"><em><span>Rodolfo Silva receives funding from CEMIE-Océano, CONACYT-SENER Sustentabilidad Energética project.</span></em></p><p class="fine-print"><em><span>Tomoya Shimura receives funding from Japan Society for the Promotion of Science and Ministry of Education, Culture, Sports, Science and Technology, Japan. </span></em></p>Climate change is changing wave patterns and strength. Bigger waves combined with sea level rise will hit coasts hard – but only in some countries.Thomas Mortlock, Senior Analyst at Aon Reinsurance Solutions and Adjunct Fellow, Macquarie UniversityAdrean Webb, Associate Professor, Tokyo Institute of TechnologyItxaso Odériz, Posdoctoral researcher, Universidad de CantabriaNobuhito Mori, Professor, Kyoto UniversityRodolfo Silva, Professor, Universidad Nacional Autónoma de México (UNAM)Tomoya Shimura, Associate professorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1836042022-05-26T18:07:37Z2022-05-26T18:07:37ZRivers can suddenly change course – scientists used 50 years of satellite images to learn where and how it happens<figure><img src="https://images.theconversation.com/files/465160/original/file-20220524-11-8sp9rh.jpg?ixlib=rb-1.1.0&rect=17%2C4%2C3000%2C2380&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite image of the Irrawaddy River delta in Myanmar, a major rice growing area.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/VUwQed">European Space Agency</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Throughout history, important cities around the world have flourished along river banks. But rivers can also be destructive forces. They routinely flood, and on rare occasions, they can abruptly shift pathways. </p>
<p>These “channel-jumping” events, which are called avulsions, have caused some of the deadliest floods in human history. Avulsions on China’s Yellow River killed <a href="https://hakaimagazine.com/news/suddenly-river-runs-through-it/">over 6 million people</a> in the late 19th and early 20th centuries. Similar events have been linked to the <a href="https://doi.org/10.1002/gea.20057">decline of Mesopotamian civilization</a> along the Tigris and Euphrates rivers in what is now Iraq, Kuwait, Turkey and Syria.</p>
<p>In a <a href="https://www.science.org/doi/10.1126/science.abm1215">2022 published study</a>, I worked with colleagues to map the global distribution of avulsions on river fans and deltas. We used satellite images of over 100 rivers from 1973 to the present, providing a half-century of bird’s-eye views of global river evolution. </p>
<p>We discovered 113 river avulsion events in temperate, tropical and dry climates. Of these events, 33 were on <a href="https://www.nationalgeographic.org/encyclopedia/alluvial-fan/">alluvial fans</a>. These land forms develop when rivers flow out of mountains or canyons onto an open plain or into the ocean and spread out, depositing dirt and gravel in a triangle-shaped area. </p>
<p>The other 80 events occurred on <a href="https://www.nationalgeographic.org/encyclopedia/delta/">river deltas</a> – fertile, low-lying regions where slower-moving rivers branch into many channels that empty into lakes or the ocean, creating networks of wetlands. We used this novel data set to answer a simple question: What determines where avulsions happen? </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/H-f49djgg9s?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Mississippi River has changed course repeatedly over the past 7,000 years, depositing sediment that created much of the land of southern Louisiana.</span></figcaption>
</figure>
<h2>Water seeks the lowest path</h2>
<p>Avulsions occur because of sediment deposition. Over time, rivers deposit sediment at the avulsion site, choking up the river with sediment. Water always flows downhill, so as its current course becomes increasingly blocked, it eventually jumps to a new location. </p>
<p>Much like earthquakes, river avulsions happen periodically in the same places. They disperse sediment and water across the rivers’ flood plains, producing these formations’ characteristic triangular shape. </p>
<p>One recent example occurred in 2008, when the Kosi River in India <a href="https://www.indiawaterportal.org/articles/anatomy-flood-case-kosi-2008">shifted its course</a> by over 60 miles (100 kilometers) in a matter of days, displacing over 3 million people. </p>
<p>In the U.S., the Mississippi River has <a href="https://www.nps.gov/vick/learn/nature/river-course-changes.htm">changed course many times</a> over the past 7,000 years. Today, a multi-dam <a href="https://www.katc.com/news/louisiana-flooding/2019/06/05/how-the-old-river-control-structure-tames-the-might-mississippi/">control structure</a> in central Louisiana keeps it from jumping its banks and joining with the Atchafalaya River, but scientists have warned that a mega-flood could <a href="https://www.nola.com/news/environment/article_dc220244-81cf-560a-bee3-3d5ed2d5e8ef.html">overwhelm these barriers</a>, causing widespread economic damage across southern Louisiana. </p>
<p>A river may not change course more than once over many decades, or even centuries. Scientists’ understanding of where these events occur is poor, and rests largely on a handful of <a href="https://doi.org/10.1002/2014GL061918">detailed observations on large deltas</a>, plus laboratory and computer models. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/DZ6vr9IWjCg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In this lab experiment, a river delta is built through repeated avulsions. As the river emerges from the canyon (left side), it slows and deposits sediment. When the river’s path becomes blocked, it changes course and drops sediment in new areas, creating a fan-shaped delta over time.</span></figcaption>
</figure>
<h2>Three kinds of avulsions</h2>
<p>Our global database revealed three distinct types of avulsions. First, the 33 avulsions on alluvial fans occurred when the rivers exited canyons. Once the rivers no longer flowed through confined valleys, they were able to spill over to one side or another toward the lowest ground.</p>
<p>The 80 avulsions that happened on deltas were influenced by forces in their backwaters. A river’s backwater is the zone where the speed of the current is affected by the presence of the ocean or lake at the river’s end. In this zone, the river current either slows down or speeds up in response to changing flood conditions. Scientists can estimate the backwater length from the size and slope of the river. </p>
<p>For example, the Mississippi River has a backwater length of nearly 300 miles (480 kilometers), which means that the speed of its flow is affected by the Gulf of Mexico all the way to a point north of Baton Rouge, Louisiana. Steeper rivers can have a backwater length scale as short as 0.6 miles (1 kilometer). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two rivers converge with dams separating them." src="https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465165/original/file-20220524-22-2k506t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Old River Control Structure complex in central Louisiana was built to keep the Mississippi River (left) from diverting into the Atchafalaya River, which runs off to the bottom right. Three dams allow 30% of the Mississippi’s flow to spill into the Atchafalaya and keep the rest flowing down the Mississippi’s current course (lower left to upper right).</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Old_River_Control_Structure#/media/File:Old_River_Control_Structure_Complex.jpg">US Army Corps of Engineers/Wikipedia</a></span>
</figcaption>
</figure>
<p>When a river is flowing normally, it slows down in its backwater stretch and drops sediment onto the riverbed. However, when floods occur, the larger volume of faster-moving water erodes the riverbed. </p>
<p>This effect starts at the river’s mouth and moves upstream, in the opposite direction from the water’s flow, erasing some of the sedimentation that has built up prior to the flood. Ultimately, this interplay between sedimentation and erosion causes the river to choke up with sediment at a location that roughly coincides with the backwater length. </p>
<p>Our database showed that 50 of the 80 avulsion events that occurred on deltas happened approximately at the backwater length. For example, the <a href="https://www.britannica.com/place/Catatumbo-River">Catatumbo River</a> in South America changed course in 1982 about 6.5 miles (10.5 kilometers) inland from the point where it flows into Venezuela’s Lake Maracaibo – close to its backwater length, which is 8.5 miles (13.7 kilometers). </p>
<h2>Some rivers can change course far upstream</h2>
<p>However, we also discovered a new class of avulsions on deltas that did not reflect either valley confinement or the backwater length. These rivers changed course far upstream from the point where they were affected by the lakes or oceans at their mouths. </p>
<p>These deltas were either on steep tropical islands like Madagascar and Papua New Guinea or in desert environments such as Eritrea. In these places, rivers carry exceptionally large quantities of sediment during floods.</p>
<p>When the rivers flood, they erode their beds starting at their mouths and working backward far upriver, similar to large rivers like the Mississippi. However, the combination of long typical flood durations and exceptionally high sediment loads during floods enables the erosion to progress far upstream. As a result, these rivers can change course well above the backwater zone where avulsions happen in large coastal rivers. </p>
<h2>More water, more sediment</h2>
<p>Our description of these three types of avulsions provides the first framework for predicting where rivers will change course on fans and deltas worldwide. These findings have crucial implications, especially for river deltas, which are home to <a href="https://doi.org/10.1038/s41467-020-18531-4">some 340 million people around the world</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo showing the Nile and its delta brightly lit at night." src="https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465369/original/file-20220525-18-ybplza.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An aerial view of the Nile River delta at night from the International Space Station. Metropolitan Cairo is the bright area at the base of the fan.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/sites/default/files/images/537063main_nileatnight_full.jpg">NASA</a></span>
</figcaption>
</figure>
<p>Most deltas are only a few feet above sea level, and some are very densely populated, such as the Mekong and Ganges-Brahmaputra deltas. Our results show that avulsion sites on deltas can move from their historic locations to new areas. Rapid sea level rise can move avulsion sites inland on deltas, exposing new communities to catastrophic flood risks. </p>
<p>We also found that rivers in our second group – those where avulsions occur in the backwater zone – can shift into the third group, where avulsions happen significantly farther upstream. We find that this can happen if the typical duration of flooding on a river or the river’s sediment supply changes. </p>
<p>Climate change is already <a href="https://www.ipcc.ch/2021/08/09/ar6-wg1-20210809-pr/">increasing flooding</a> in many parts of the world and washing more sediments into rivers. Land use changes, such as converting forests to farmlands, also are increasing sediment loads. In my view, it is imperative to understand how such changes can affect dynamic, volatile river systems – and the people who live around them – well into the future.</p><img src="https://counter.theconversation.com/content/183604/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vamsi Ganti receives funding from the National Science Foundation, and the donors of the American Chemical Society Petroleum Research Fund. </span></em></p>Millions of people around the world live on river deltas and are vulnerable when those rivers shift direction. A new study shows why and where these events, called avulsions, happen.Vamsi Ganti, Assistant Professor of Geography, University of California, Santa BarbaraLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1837252022-05-25T20:16:48Z2022-05-25T20:16:48ZHow plate tectonics, mountains and deep-sea sediments have maintained Earth’s ‘Goldilocks’ climate<p>For hundreds of millions of years, Earth’s climate has warmed and cooled with natural fluctuations in the level of carbon dioxide (CO₂) in the atmosphere. Over the past century, <a href="https://theconversation.com/humanity-is-compressing-millions-of-years-of-natural-change-into-just-a-few-centuries-170525">humans have pushed CO₂ levels</a> to their highest in 2 million years – <a href="https://www.sciencedirect.com/science/article/pii/S1674927818300376">overtaking natural emissions</a> – mostly by burning fossil fuels, causing ongoing global warming that may make parts of the globe uninhabitable.</p>
<p>What can be done? As Earth scientists, we look to how natural processes have recycled carbon from atmosphere to Earth and back in the past to find possible answers to this question.</p>
<p>Our <a href="https://www.nature.com/articles/s41586-022-04420-x">new research</a> published in Nature, shows how tectonic plates, volcanoes, eroding mountains and seabed sediment have controlled Earth’s climate in the geological past. Harnessing these processes may play a part in maintaining the “<a href="https://www.abc.net.au/news/science/2016-02-22/goldilocks-zones-habitable-zone-astrobiology-exoplanets/6907836">Goldilocks</a>” climate our planet has enjoyed.</p>
<h2>From hothouse to ice age</h2>
<p><a href="https://theconversation.com/we-are-heading-for-the-warmest-climate-in-half-a-billion-years-says-new-study-73648">Hothouse and icehouse climates</a> have existed in the geological past. The Cretaceous hothouse (which lasted from roughly 145 million to 66 million years ago) had atmospheric CO₂ levels above 1,000 parts per million, compared with around 420 today, and temperatures up to 10°C higher than today. </p>
<p>But Earth’s climate began to <a href="https://www.eurekalert.org/news-releases/911139">cool around 50 million years ago</a> during the <a href="https://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx">Cenozoic Era</a>, culminating in an <a href="https://theconversation.com/the-last-ice-age-tells-us-why-we-need-to-care-about-a-2-change-in-temperature-126923">icehouse climate</a> in which temperatures dropped to roughly 7°C cooler than today.</p>
<p>What kickstarted this dramatic change in global climate?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=196&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=196&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=196&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=246&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=246&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=246&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Earth evolved from a hothouse climate in the Cretaceous Period (left) to an icehouse climate in the following Cenozoic Era (right), leading to inland ice sheets.</span>
<span class="attribution"><span class="source">F. Guillén and M. Antón / Wikimedia commons</span></span>
</figcaption>
</figure>
<p>Our suspicion was that Earth’s tectonic plates were the culprit. To better understand how tectonic plates store, move and emit carbon, we built a computer model of the tectonic “carbon conveyor belt”.</p>
<h2>The carbon conveyor belt</h2>
<p>Tectonic processes release carbon into the atmosphere at mid-ocean ridges - where two plates are moving away from each other - allowing magma to rise to the surface and create new ocean crust.</p>
<p>At the same time, at ocean trenches - where two plates converge - plates are pulled down and recycled back into the deep Earth. On their way down they carry carbon back into the Earth’s interior, but also release some CO₂ via volcanic activity. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=264&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=264&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=264&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=331&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=331&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=331&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Earth’s tectonic carbon conveyor belt shifts massive amounts of carbon between the deep Earth and the surface, from mid-ocean ridges to subduction zones, where oceanic plates carrying deep-sea sediments are recycled back into the Earth’s interior. The processes involved play a pivotal role in Earth’s climate and habitability.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>Our model shows that the Cretaceous hothouse climate was caused by very fast-moving tectonic plates, which dramatically increased CO₂ emissions from mid-ocean ridges. </p>
<p>In the transition to the Cenozoic icehouse climate tectonic plate movement slowed down and volcanic CO₂ emissions began to fall. But to our surprise, we discovered a more complex mechanism hidden in the conveyor belt system involving mountain building, continental erosion and burial of the remains of miscroscopic organisms on the seafloor.</p>
<h2>The hidden cooling effect of slowing tectonic plates in the Cenozoic</h2>
<p>Tectonic plates slow down due to collisions, which in turn leads to mountain building, such as the Himalayas and the Alps formed over the last 50 million years. This should have reduced volcanic CO₂ emissions but instead our carbon conveyor belt model revealed increased emissions. </p>
<p>We tracked their source to carbon-rich deep-sea sediments being pushed downwards to feed volcanoes, increasing CO₂ emissions and cancelling out the effect of slowing plates. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/waGHSfs_YRg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows plate motions, carbon storage within tectonic plates and carbon degassing along mid-ocean ridges and subduction zones through time. Our carbon model shows these processes alone cannot explain global cooling in the Cenozoic Era. The effects of rock erosion, not shown here, played a key role. Arrows indicate plate motion speed.</span></figcaption>
</figure>
<p>So what exactly was the mechanism responsible for the drop in atmospheric CO₂? </p>
<p>The answer lies in the mountains that were responsible for slowing down the plates in the first place and in carbon storage in the deep sea. </p>
<p>As soon as mountains form, they start being eroded. Rainwater containing CO₂ reacts with a range of mountain rocks, breaking them down. Rivers carry the dissolved minerals into the sea. Marine organisms then use the dissolved products to build their shells, which ultimately become a part of carbon-rich marine sediments. </p>
<p>As new mountain chains formed, more rocks were eroded, speeding up this process. Massive amounts of CO₂ were stored away, and the planet cooled, even though some of these sediments were subducted with their carbon degassing via arc volcanoes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photographs showing white cliffs rising from the sea." src="https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=443&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=443&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=443&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The limestone of the White Cliffs of Dover is an example of carbon-rich marine sediment, composed of the remains of tiny calcium carbonate skeletons of marine plankton.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:White_Cliffs_of_Dover_02.JPG">I Giel / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Rock weathering as a possible carbon dioxide removal technology</h2>
<p>The Intergovernmental Panel on Climate Change (IPCC) <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-3/">says</a> large-scale deployment of carbon dioxide removal methods is “unavoidable” if the world is to reach net-zero greenhouse gas emissions.</p>
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Read more:
<a href="https://theconversation.com/on-top-of-drastic-emissions-cuts-ipcc-finds-large-scale-co-removal-from-air-will-be-essential-to-meeting-targets-180663">On top of drastic emissions cuts, IPCC finds large-scale CO₂ removal from air will be "essential" to meeting targets</a>
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<p>The weathering of igneous rocks, especially rocks like basalt containing a mineral called olivine, is very efficient in reducing atmospheric CO₂. Spreading olivine on beaches could <a href="https://www.theguardian.com/environment/2021/jun/23/cloud-spraying-and-hurricane-slaying-could-geoengineering-fix-the-climate-crisis">absorb up to a trillion tonnes of CO₂ from the atmosphere</a>, according to <a href="https://www.vesta.earth/">some estimates</a>. </p>
<p>The speed of current <a href="https://climate.nasa.gov/evidence/">human-induced warming</a> is such that reducing our carbon emissions very quickly is essential to avoid catastrophic global warming. But geological processes, with some human help, may also have their role in maintaining Earth’s “Goldilocks” climate.</p>
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<p><em>This study was carried out by researchers from the University of Sydney’s <a href="https://www.earthbyte.org/">EarthByte Group</a>, The University of Western Australia, the University of Leeds and the Swiss Federal Institute of Technology, Zurich using <a href="https://www.gplates.org">GPlates</a> open access modelling software. This was enabled by Australia’s National Collaborative Research Infrastructure Strategy (NCRIS) via <a href="https://www.auscope.org.au/">AuScope</a> and The Office of the Chief Scientist and Engineer, NSW Department of Industry.</em></p><img src="https://counter.theconversation.com/content/183725/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dietmar Müller receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Adriana Dutkiewicz receives funding from the Australian Research Council (FT190100829). </span></em></p><p class="fine-print"><em><span>Andrew Merdith receives funding from MSCA-IF project 893615. </span></em></p><p class="fine-print"><em><span>Christopher Gonzalez received funding from Australian Research Council. </span></em></p><p class="fine-print"><em><span>Sabin Zahirovic receives funding from the Australian Research Council (DE210100084). </span></em></p><p class="fine-print"><em><span>Tobias Keller previously received funding from the European Research Council and from the Swiss National Science Foundation.</span></em></p><p class="fine-print"><em><span>Weronika Gorczyk receives funding from Australian Research Council and Minerals Research Institute Of Western Australia</span></em></p><p class="fine-print"><em><span>Jo Condon is affiliated with AuScope, a federally funded and non-profit NCRIS organisation that supports the development of GPlates software used in the research described in this article.</span></em></p><p class="fine-print"><em><span>Ben Mather does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New modelling shows how tectonic plate movements, carbon-rich deep-sea sediment, and mountain weathering have regulated Earth’s climate.Dietmar Müller, Professor of Geophysics, University of SydneyAdriana Dutkiewicz, ARC Future Fellow, University of SydneyAndrew Merdith, Research fellow, University of LeedsBen Mather, Research fellow, University of SydneyChristopher Gonzalez, Research Fellow, The University of Western AustraliaSabin Zahirovic, Postdoctoral Research Associate, University of SydneyTobias Keller, Senior Scientist in Computational Geosciences, Swiss Federal Institute of Technology ZurichWeronika Gorczyk, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1786892022-05-24T14:20:49Z2022-05-24T14:20:49ZOil hazards aren’t the main worry of Nigeria’s coastal residents: toilets are<figure><img src="https://images.theconversation.com/files/464764/original/file-20220523-30932-jh0y53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Adekunle Ajayi/Nur Photo via Getty Images. </span> </figcaption></figure><p>Nigeria’s coastal areas are known to present environmental hazards and risks. Oil exploration and exploitation is one <a href="https://www.tandfonline.com/doi/pdf/10.1080/09542299.2008.11073770">source</a> of these hazards. Oil spillage, gas flaring, air and water pollution and agricultural land contamination are serious problems in the region, with <a href="https://ehp.niehs.nih.gov/doi/abs/10.1289/isee.2021.P-059">implications</a> for human and environmental health. </p>
<p>Flooding and erosion are additional sources of danger in the region. Damage from floods is <a href="http://www.ijsit.com/admin/ijsit_files/FLOODING%20AND%20ITS%20EFFECT-CASE%20STUDY%20OF%20PARTS%20OF%20DELTA%20STATE,%20SOUTH-SOUTH%20NIGERIA_IJSIT_4.6.14.pdf">extensive</a>. </p>
<p>Poor sanitation is a third hazard. Poor sanitation practices, poor location of facilities like toilets and kitchens, and the contamination of water sources in oil producing communities expose residents to <a href="https://www.afro.who.int/news/who-supports-delta-state-fight-against-cholera-outbreak">cholera</a>, typhoid, malaria and dysentery. </p>
<p>Residents’ perceptions of the environmental hazards have not been well explored. It’s important to understand perceptions because they drive behaviour. In looking for ways to avoid, prepare for and respond to hazards and disasters, it is useful to understand what motivates people’s actions.</p>
<p>Research has shown that people take action on threats <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7122361/">based</a> on their personal perception of the risk. Perception, in turn, depends on the level of information people have about the risk, personal experience of past events and socioeconomic attributes. It’s also influenced by the quantity of losses people think they can avoid, absorb and tolerate. The <a href="https://www.ipcc.ch/site/assets/uploads/2018/03/SREX-Chap2_FINAL-1.pdf">type</a> of hazard makes a difference. So does people’s trust in the capability of authorities.</p>
<p>Therefore, in <a href="https://www.sciencedirect.com/science/article/pii/S2212420921000601?via%3Dihub">our study</a> we sought to understand what influences the perceptions of people in Delta State when it comes to environmental risks. Understanding what drives their actions could help in finding ways to avoid or cope with risks and disasters.</p>
<p>We found that residents were less concerned about oil induced hazards and risks, or floods and erosion, than they were about the lack of sanitation amenities like drains and toilets. They perceived oil and flood risks as normal parts of their lives, not as major risks. Some even contributed to those problems by, for example, stealing oil. </p>
<p>What they were most worried about was being vulnerable to things like snakebites, reptile invasion, storm water diversion into their homes, collapse of buildings, spread of diseases from open defecation, and personal safety related to bathrooms and kitchens being located away from homes.</p>
<p>Many of the residential areas in the region have evolved without planning regulations. Residents haven’t always followed safe practices when building amenities. The resulting danger is an unsanitary environment. We suggest that government agencies ensure house owners adhere to building codes.</p>
<h2>Study of coastal towns</h2>
<p><a href="https://www.sciencedirect.com/science/article/pii/S2212420921000601?via%3Dihub">Our research</a> was carried out in the southern part of Nigeria over 18 months. We focused on three towns: Sapele, Oghara and Koko. The towns are involved in crude oil activities and are close to the ocean. They also face dangers from <a href="https://www.reuters.com/article/us-nigeria-spill-idUSKBN16857D">toxic waste dumping</a>. </p>
<p>In these towns, infrastructure such as roads, drainage and public toilets is inadequate and in very poor condition.</p>
<p>We sampled residential buildings from each town and gave questionnaires to 218 residents of these buildings. The questionnaire aimed to capture the socio-economic attributes of the people and their awareness of environmental hazards such as oil and sanitation. It also asked about the severity attached to risk emanating from hazards and responses to them.</p>
<p>Previous research has found that people’s perceptions of environmental hazards and risks are <a href="https://pubmed.ncbi.nlm.nih.gov/23278120/">influenced</a> by socioeconomic characteristics and by environmental awareness. The presence of amenities such as well-lit and tarred roads, location of emergency management agencies, electricity transformers and fire stations has also been found to be related to perceptions. We examined the impact of these factors on the way our respondents viewed environmental hazards and risks.</p>
<h2>What influences perceptions</h2>
<p>We found that a direct relationship exists between residents’ perception of environmental threats and infrastructure availability. Such infrastructure includes roads, drainage, public toilets, health centres, schools and electricity transformers. </p>
<p>The availability and location of toilets and drains scored highest among residents’ concerns. Location of kitchens was another issue. In most cases, toilets, bathrooms and kitchens are constructed detached from the main buildings, making residents more vulnerable to health risks. Such kitchens are vulnerable to infestation by flies, ants, cockroaches and other disease vectors. </p>
<p>We also discovered that people’s views have no relationship with efforts by the government, international oil companies and nongovernmental organisations to address threats. Such threats include oil pollution, gas flaring, hazardous waste, odour and erosion. This implies that people do not trust the capacities of these stakeholders to manage environmental hazards. They therefore engage in environmentally destructive and defiant behaviours such as crude oil theft, illegal oil refining and pipeline vandalism. </p>
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<strong>
Read more:
<a href="https://theconversation.com/three-things-that-can-go-wrong-at-an-illegal-oil-refinery-in-nigeria-182459">Three things that can go wrong at an illegal oil refinery in Nigeria</a>
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<p>The socioeconomic attributes of residents correlated with their views on environmental threats. These are attributes such as gender, age, educational status, household size, income, occupation and length of stay in the area. </p>
<p>Higher income, higher level of education, and longer length of stay increased concerns about environmental threats. This shows that the more people’s income and education level are enhanced, the more concerned they are about managing environmental hazards in their area. </p>
<h2>The way forward</h2>
<p>We recommend ways to enhance people’s perception of environmental hazards – and thus enhance safety practices.</p>
<p>Governments at all levels should improve the provision and maintenance of environmental amenities. </p>
<p>Government should also work with representatives of the people to effectively monitor and manage threats emanating from oil production activities. The key involvement of the representatives will instil trust and create a sense of belonging in the efforts to manage the threats.</p>
<p>Government and NGOs should provide environmental education for residents of the coastal towns. Residents need to know about the inherent harmful impacts of unsanitary environments and poor amenities. Education could be done through the media and the school curriculum.</p><img src="https://counter.theconversation.com/content/178689/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Seun Olowoporoku does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Some Niger Delta residents are less concerned about oil-induced hazards and risks, or floods and erosion. They are more worried about a lack of sanitation amenities.Seun Olowoporoku, Gradute Research Fellow, Obafemi Awolowo UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1820392022-05-12T09:02:55Z2022-05-12T09:02:55Z‘Like 20 tip trucks pouring sand on every metre-wide strip’: how extreme storms can replenish beaches, not just erode them<figure><img src="https://images.theconversation.com/files/462641/original/file-20220512-19-kvyhfz.jpg?ixlib=rb-1.1.0&rect=0%2C502%2C1845%2C1030&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> </figcaption></figure><p><em>Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this series, we’ve invited them to share their unique <a href="https://theconversation.com/au/topics/photos-from-the-field-92499">photos from the field</a>.</em></p>
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<p>Extreme storms can cause devastating erosion and leave beachfront houses <a href="https://www.abc.net.au/news/2021-07-16/wamberal-beach-erosion-one-year-on/100295364">teetering on cliff edges</a>. But our <a href="https://www.nature.com/articles/s43247-022-00437-2">new research</a>, published today, finds storms might also help replenish beaches by bringing in new sand from deeper waters.</p>
<p>We studied three extreme storms in Australia, the United Kingdom and Mexico. One, in Sydney in 2016, <a href="https://www.youtube.com/watch?v=e4DxqUshKh4">famously ripped a swimming pool</a> away from a property overlooking the coastline. </p>
<p>For the first time, we’re able to show just how much new sand can be added to a beach in a single storm alone – over 400,000 cubic metres in some cases. That’s equivalent to the <a href="https://www.nature.com/articles/s43017-020-00109-9">typical volumes of sand</a> engineers use to nourish beaches artificially.</p>
<p>As sea levels rise, this natural form of beach replenishment might be an important factor in offsetting some of the damaging effects of climate change on beaches. Yet, with little knowledge of exactly how much sand is moving around offshore, predicting the future of beaches in the coming decades is extremely difficult.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462626/original/file-20220512-19-bzoz4c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Damaged houses at Collaroy Beach, Sydney in the wake of an extreme storm in June 2016.</span>
<span class="attribution"><span class="source">UNSW Water Research Laboratory</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462627/original/file-20220512-12-arf332.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">While extreme storms can cause major erosion to beachfront properties, they can also bring in new sand from deeper water.</span>
<span class="attribution"><span class="source">UNSW Water Research Laboratory</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Wave after wave</h2>
<p>Violent storm waves strip beaches of sand above the waterline, which often erodes sand dunes. In deeper waters, however, these same waves help stir up sediment lying dormant on the seabed. This sand is then pushed towards the shore and settles as the storm passes.</p>
<p>To study the three storms in Australia, the UK and Mexico, we used high-resolution monitoring equipment including twin engine airplanes, drones and jet skis mounted with an echo-sounder for measuring the seabed.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=367&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=367&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=367&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=462&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=462&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462621/original/file-20220512-22-qljf6d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=462&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The UK survey team measuring sand volumes along the coast of Cornwall.</span>
<span class="attribution"><span class="source">University of Plymouth</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=347&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=347&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=347&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=436&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=436&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462623/original/file-20220512-16-pm0lu1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=436&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A combination of high-resolution survey equipment was used to measure changes to the beach.</span>
<span class="attribution"><span class="source">University of Plymouth</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In Australia, we measured Narrabeen Beach in Sydney. In the UK, we monitored the impact of <a href="https://www.bbc.com/news/uk-26170904">several storms during the winters of 2013-2014</a> and 2015-2016, at Perranporth beach in Cornwall. And in northwest Mexico, we recorded the impact of the 2018-2019 winter on La Mision Beach.</p>
<p>In the time-lapse video below, you can see just how quickly the water can encroach on beachfront houses during extreme storms. Beneath the water surface, however, huge volumes of sand is also moving about.</p>
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<img src="https://figshare.com/ndownloader/files/8066051/preview/8066051/preview.gif" width="100%">
<figcaption>A time-lapse of severe coastal erosion at Narrabeen-Collaroy Beach (SE Australia) during the June 2016 East Coast Low.<br>Source: Mitchell Harley (author provided)</figcaption>
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<p>By capturing the three-dimensional seabed changes for each event, we could quantify for the first time the precise sand volumes mobilised during these extreme storms.</p>
<p>To give an indication of the scale of beach change, the amount of sand added to the beach resulting from the stormy periods was on the order of 100 cubic metres for every metre length of beach – that’s like 20 tip trucks pouring sand on every metre-wide strip.</p>
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<em>
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Read more:
<a href="https://theconversation.com/the-seas-are-coming-for-us-in-kiribati-will-australia-rehome-us-172137">The seas are coming for us in Kiribati. Will Australia rehome us?</a>
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<p>As the beaches spanned several kilometres, this amounted to 130,000 cubic metres for La Mision beach, 400,000 cubic metres for Narrabeen and 420,000 cubic metres for Perranporth.</p>
<p>The time-lapse video below is of Wamberal Beach during a storm in 2020. While it wasn’t included in our study, it’s another great example of how large storm waves cause abrupt changes to beaches. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/lSjjG9zpqBg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Source: UNSW Water Research Laboratory (author provided)</span></figcaption>
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<h2>Rethinking coastal erosion</h2>
<p>Exactly how a coastline might change due to sea-level rise is a key question facing coastal managers, as they plan for the escalating impacts of climate change.</p>
<p>The Intergovernmental Panel for Climate Change <a href="https://www.ipcc.ch/report/ar6/wg1/">projects</a> global sea levels to rise up to 76 centimetres by 2100, under a middle-of-the-road emissions scenario where global temperatures rise 2.1-3.5°C. </p>
<p>The response of the coast to sea-level rise has previously been estimated using an approach known as the Bruun rule. This rule states that for a given metre of sea-level rise, the coastline is expected to retreat between around 20m to over 100m, <a href="https://essd.copernicus.org/articles/11/1515/2019/">depending on the steepness of the coast</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462654/original/file-20220512-11-54h9h7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">UNSW researcher Chris Drummond launching a drone to survey the beach in Sydney.</span>
<span class="attribution"><span class="source">UNSW Research Laboratory</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Using the Bruun rule, global sea-level rise caused by climate change has been <a href="https://www.nature.com/articles/s41558-020-0697-0?from=article_link">projected to</a> result in losing almost half the world’s sandy beaches by 2100. However, <a href="https://www.nature.com/articles/s41558-020-00934-2">not all coastal scientists share this view</a>.</p>
<p>Let there be no doubt: sea-level rise is a tragic consequence of climate change, and it poses an existential threat to many coastal communities, especially for island nations in the Pacific. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=316&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=316&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=316&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=398&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=398&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462652/original/file-20220512-26-gb6u6j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=398&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mexico’s La Mision beach, on a calm day. In the winter of 2018-2019, research found that storms pushed 130,000 cubic metres of new sand into the beach system.</span>
<span class="attribution"><span class="source">Autonomous University of Baja California</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>What our new research confirms is that the Bruun rule approach is overly simplistic, as it doesn’t take into account <a href="https://www.sciencedirect.com/science/article/pii/S0964569122001557">the many complex local factors</a> about how individual beaches respond to sea-level rise. </p>
<p>This includes the amount of sand stored in deeper water immediately off the coast, and its potential to replenish beaches during extreme weather events.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462635/original/file-20220512-11-kvyhfz.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Understanding how sand moves along the coast is critical for better coastal planning.</span>
<span class="attribution"><span class="source">UNSW Water Research Laboratory</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Improving predictions in an uncertain future</h2>
<p>While this research has focused only on three extreme storm sequences, it shows that <a href="https://theconversation.com/why-some-beaches-including-in-queensland-are-getting-bigger-despite-rising-sea-levels-180964">understanding how sediment moves along the coast</a> is fundamental to planning for climate change impacts.</p>
<p>There are two ways we can significantly improve long-term predictions of coastal change in this uncertain future:</p>
<ol>
<li><p><a href="https://www.environment.nsw.gov.au/research-and-publications/our-science-and-research/our-research/water/offshore-mapping">upscaling efforts in mapping the seabed</a> to learn how much sediment is presently stored in the deeper coastal waters </p></li>
<li><p>increasing routine coastal monitoring of the entire nearshore system, from the sand dunes down to deeper waters. This is currently carried out by <a href="https://coastalmonitoring.org/southwest/">UK coastal observatories</a>. </p></li>
</ol>
<p>A greater understanding of sand movements off the coast, combined with computer modelling, can better forecast future shorelines. This will give coastal managers the information needed to make critical long-term planning decisions for communities.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-some-beaches-including-in-queensland-are-getting-bigger-despite-rising-sea-levels-180964">Why some beaches, including in Queensland, are getting bigger despite rising sea levels</a>
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<hr>
<img src="https://counter.theconversation.com/content/182039/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mitchell Harley receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Gerd Masselink receives funding from NERC.</span></em></p>As sea levels rise, this natural form of beach replenishment might be an important factor in offsetting some of the damaging effects of climate change on beaches.Mitchell Harley, Scientia Senior Lecturer, UNSW SydneyGerd Masselink, Professor of Coastal Geomorphology, University of PlymouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1767312022-05-08T12:22:53Z2022-05-08T12:22:53ZThe window of opportunity to address increasing drought and expanding drylands is vanishing<figure><img src="https://images.theconversation.com/files/458719/original/file-20220419-20-s904jc.jpg?ixlib=rb-1.1.0&rect=17%2C98%2C5973%2C3898&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Portugal has seen little rain since October 2021. By the end of January, 45 per cent of the country was enduring 'severe' or 'extreme' drought conditions.</span> <span class="attribution"><span class="source">(AP Photo/Sergio Azenha)</span></span></figcaption></figure><p><a href="https://doi.org/10.1073/pnas.2002411117">Chile, Argentina</a> and the <a href="https://doi.org/10.1038/s41558-022-01290-z">American West</a> are in the midst of a decade-long, megadrought — the driest conditions those regions have seen in a century. And many areas in <a href="https://www.agr.gc.ca/atlas/maps_cartes/canadianDroughtMonitor/monthlyAssessments/en/2022/cdm_2201_mn_en.pdf">Western Canada</a> and the <a href="https://droughtmonitor.unl.edu/">United States</a> are experiencing extreme drought — a once in 20-year event. </p>
<p>Drought makes agriculture less productive, reduces crop yields and increases heat-related deaths. It adds to conflict and migration, as <a href="https://www.ipcc.ch/srccl/chapter/chapter-3/">marginalized people are dispossessed of their land</a>. In short, it leaves people more vulnerable. </p>
<p>Drought is part of natural climate variability, but it is also one of the many outcomes of climate change that is increasing in frequency and intensity. <a href="https://climate.nasa.gov/effects/">Droughts that used to occur in dry regions once every 10 years are now projected to occur more than four times a decade</a>, if the Earth’s average temperature warms by 4 C. </p>
<p>Unless countries dramatically reduce their emissions from burning coal, oil and natural gas, we are bound to overshoot the goal of limiting global warming to 1.5 C. Dryland areas could <a href="https://plaintextipcc.com/IPCC_AR6_WGII_Paper_3.html">expand by a quarter and encompass half of the Earth’s land area</a>, including parts of the Prairies.</p>
<p>Governments need to acknowledge that changes are already happening to dryland areas and that others can no longer be avoided, even with reduced emissions. We need to see better strategies to respond to wildfire, water scarcity and conflict, land degradation and desertification, if we are to reduce the loss of livelihoods and life from drought. </p>
<h2>Big climate changes are coming</h2>
<p><a href="https://www.usgs.gov/special-topics/drought/science/dryland-ecosystems">Drylands</a> are <a href="https://www.ipcc.ch/srccl/chapter/chapter-2/">warming twice as fast as humid areas</a>. Scientists predict that in the next 50 years, between <a href="https://doi.org/10.1073/pnas.1910114117">one billion and three billion people will be living in temperatures exceeding the climate range that has served humanity for more than 6,000 years</a>, or migrating elsewhere.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/too-many-people-not-enough-food-isnt-the-cause-of-hunger-and-food-insecurity-179168">'Too many people, not enough food' isn't the cause of hunger and food insecurity</a>
</strong>
</em>
</p>
<hr>
<p>Livelihoods and life will change fundamentally in these areas. Animal husbandry — such as livestock production — <a href="https://www.theguardian.com/global-development/2022/feb/18/somalia-crowded-camps-drought-worsens">will no longer be possible as increasing temperatures lead to the widespread death of animals</a>. And city infrastructure wasn’t built to handle intense flood events, which are <a href="https://doi.org/10.1038/s41598-019-38537-3">causing damage</a> and <a href="http://www.doi.org/10.4236/wjet.2017.53B013">increasing in many dryland areas</a>.</p>
<figure class="align-center ">
<img alt="A dead tree stump in front of a sandy landscape and a shallow pool of water in the background." src="https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461616/original/file-20220505-17-h29ycc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The dry lake bed of the Wickiup Reservoir in Oregon, in September 2021.</span>
<span class="attribution"><span class="source">(AP Photo/Nathan Howard)</span></span>
</figcaption>
</figure>
<h2>Big human changes are also coming</h2>
<p>Current climate adaptation efforts to near-term drought and flood events tend to be reactive, incremental and small. For example, Yorkton, Sask., responded to three consecutive flood events with some infrastructure change, but <a href="https://doi.org/10.3390/w14081186">enduring social learning has been lost as time passes</a>.</p>
<p>These short-sighted interventions mean vulnerable and marginalized people suffer most. Recurring drought reduces the availability of drought-risk reduction supports such as crop insurance by making insurance premiums more expensive, <a href="https://www.ewg.org/research/crop-losses-climate-crisis-cost-billions-dollars-insurance-payouts">possibly unattainable to many farmers</a>. </p>
<p>Governments must start implementing policies that aim to reduce the future impacts of drought and build farmer resilience. They might offer solutions to wind erosion and dust management or launch campaigns to reduce water consumption and promote the restoration or reclamation of landscapes. They could <a href="https://doi.org/10.3390/su132212463">embrace landscape heterogeneity strategies</a> — varieties of crops and patches of non-cultivated land — that allow bees and pollinators to thrive. After wildfires, policies and funding could <a href="https://www.ipcc.ch/srccl/chapter/chapter-3/">accelerate restoration by planting trees and vegetation</a> for wind breaks, as well as encourage farmers to plant drought-tolerant food crops.</p>
<p>Assessing the risk of climate events such as drought, flood or fire and their impacts before they occur allows for the assessment of the appropriate division of public and private responsibilities in preventing, planning for, responding to these events when they do occur.</p>
<h2>Groundwater tipping point</h2>
<p>While increasing incremental adaptation is important, large systemic change or transformational adaptation may be necessary to address worsening climate risks. These adaptations might include developing and implementing water storage technologies, changes to grazing and farming practices to preserve soil and behavioural changes to reduce water usage. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-ancient-water-management-techniques-may-help-prairie-farmers-experiencing-drought-168920">How ancient water management techniques may help Prairie farmers experiencing drought</a>
</strong>
</em>
</p>
<hr>
<p>There may also be residual risks that adaptation can’t address, as well as maladaptation — actions that unintentionally increase the risk of adverse outcomes due to climate change. For instance, <a href="https://doi.org/10.1038/s41598-019-40155-y">groundwater is a source of irrigation in many parts of the world and its depletion may have passed a tipping point where it cannot be recharged by precipitation</a>. </p>
<p>In water-scarce regions, <a href="https://www.fao.org/3/i7754e/i7754e.pdf">farmers may use low-quality water resources (called marginal quality waters)</a>, such as wastewater or drainage water, that may be high in salts, pathogens and heavy metals, to irrigate their crops. This can lead to salt accumulating in the soil and <a href="https://doi.org/10.1038/s41558-018-0313-8">can make the land unusable for agriculture</a>, which can then have <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/salinization">consequences for food security</a>. </p>
<p>In India, for example, hectares of land are projected to become unusable by 2050, at a cost of US$3 billion. The global economic losses of salt-induced land degradation are estimated at <a href="https://doi.org/10.3389/fsufs.2020.533781">US$27.3 billion per year</a>. In California, lack of irrigation water could cause <a href="https://www.businessinsider.com/california-water-shortage-drought-could-cause-farm-food-prices-rise-2021-6">food prices to rise globally</a>.</p>
<p>While the world’s governments consider ways to reduce emissions to limit global warming, adaptation and resilience must remain high on their list of priorities. The world is on course to overshoot its climate targets and, as the window of opportunity closes, these polices have become increasingly necessary.</p><img src="https://counter.theconversation.com/content/176731/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Margot Hurlbert receives funding from the Social Sciences and Humanities Research Council Canada.</span></em></p>If the world overshoots its climate targets, drought could cause dryland areas to expand by a quarter and encompass half the Earth’s land area, threatening lives and livelihoods.Margot Hurlbert, Canada Research Chair, Climate Change, Energy and Sustainability, University of ReginaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1755082022-02-01T15:27:53Z2022-02-01T15:27:53ZCan the UK’s crumbling coasts be saved from erosion?<figure><img src="https://images.theconversation.com/files/443566/original/file-20220131-116292-1qfua0h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Lois GoBe / shutterstock</span></span></figcaption></figure><p>Erosion is constantly reshaping coastlines as land is swept into the sea, sometimes along with buildings and infrastructure. The UK has some of the fastest eroding coastlines in Europe. Of the mainland’s 17,000km of coastline, around <a href="https://www.semanticscholar.org/paper/Impacts-of-climate-change-on-coastal-erosion-Masselink-Russell/f68b65b0a584d2eedcfd7d61aa25bcedec7f1799?p2df">2,900km (17%)</a> is affected by erosion. </p>
<p>Defending this entire coastline would be prohibitively expensive and destroy many of the things we love about the coast – few want to see boulders dumped on their local beach or large stretches of concrete wall. So instead of asking how UK coastlines can be “saved” from erosion, we need to instead consider how they can be managed in a sustainable, holistic way that protects people who live along the coast and allows them to adapt to change.</p>
<p>A number of sewage treatment works, landfill sites and railway lines are already <a href="https://www.ukclimaterisk.org/independent-assessment-ccra3/technical-report/">prone to significant flooding</a>, while seawater can flow over defences during storms, contaminating agricultural land and groundwater supplies. Infrastructure such as these will become more at risk as rising seas cause increased erosion and flooding.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A house on a clifftop viewed from below" src="https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443770/original/file-20220201-17-manmjw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Eroding cliffs creep towards a doomed house in Happisburgh, Norfolk.</span>
<span class="attribution"><span class="source">Philip Bird / shutterstock</span></span>
</figcaption>
</figure>
<p>Despite coastline management plans and adaptation measures, such as raising flood defences or managed retreat, the risks are not removed entirely and erosion has continued to <a href="https://www.tandfonline.com/doi/full/10.1080/08920753.2022.2022971?src=">exacerbate hazards</a> like storm surges and landslides. Minimising damage and improving the safety of coastal communities is vitally important.</p>
<h2>Defences v erosion</h2>
<p>Erosion and deposition of sediment are continuously changing the shape of the UK, with the east coast losing several hundred kilometres of land over the past half century. The ever-changing coastline requires maps to be regularly updated using the latest GPS measurements and satellite images. These observations represent a historical snapshot in time, and trying to predict what the coastline will look like in 50 years is difficult as climate change and rising seas are accelerating erosion rates. </p>
<p>Erosion is a major issue, particularly in smaller towns and villages along the UK’s southern and eastern coasts. Barton-on-Sea, a small coastal town in Hampshire, is one such example where residents are worried about their safety due to <a href="https://www.mdpi.com/2073-4441/9/12/905">landslides and high erosion rates</a>. Several meters of frontage have crumbled into the sea and the entire seafront is now classified as highly vulnerable to erosion. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Eroding cliff viewed from below" src="https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443754/original/file-20220201-17-qbutns.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Barton-on-Sea’s eroding cliffs viewed from below.</span>
<span class="attribution"><span class="source">Komali Kantamaneni</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Extensive stretches of <a href="https://www.bbc.co.uk/news/uk-england-humber-53056955">rock armour</a> (large boulders that absorb the force of waves) and <a href="https://climate-adapt.eea.europa.eu/metadata/adaptation-options/groynes-breakwaters-and-artificial-reefs">groynes</a> (structures built from the shore into the sea, designed to trap sediment) were established to provide protection. However, these protections concentrate wave energy in adjacent sites and starve them of sediment leading to accelerated erosion further down the coast. These defences are also unlikely to be effective against stronger storms and higher seas in the future.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Eroding cliffs beside the sea" src="https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443748/original/file-20220201-13-xvzpdg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">…and the same erosion viewed from the clifftop.</span>
<span class="attribution"><span class="source">Komali Kantamaneni</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Erosion management strategies like this are often divisive, as sediment removed from one section of coastline frequently supplies sand for beaches in another. Beaches provide income from tourism and protection from erosion and flooding. Barton-on-Sea is not the only case where halting erosion in one area has accelerated it in another, and poorly planned coastal defences can have far-reaching detrimental impacts. </p>
<h2>Coastal vulnerability and hotspots</h2>
<p>One of us (Komali Kantamaneni) developed an <a href="https://www.sciencedirect.com/science/article/abs/pii/S0964569117304222">method to compare coastal vulnerability in different areas</a> and identified 11 hotspots where the UK coast was most vulnerable to erosion, and where such erosion would be most economically damaging. These hotspots included towns like Skegness and Great Yarmouth in England and Port Talbot and Aberystwyth in Wales. Together, these areas contain <a href="https://www.sciencedirect.com/science/article/pii/S0964569116301843">£22 billion</a> worth of homes, offices, public buildings, infrastructure and other assets. Flooding, erosion and storm surges in these towns would threaten more than 100,000 people and 50,000 properties.</p>
<p>As coastal areas are increasingly settled, erosion is becoming a bigger risk to society. Towns like Aberystwyth are particularly <a href="https://link.springer.com/article/10.1007/s11069-016-2413-y">vulnerable to strong waves</a>, often several metres high. New developments and redevelopments in the town are exposing more people to the effects of erosion, leading to greater economic losses from flooding and storm damage. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of UK with dots representing vulnerable hotspots." src="https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=766&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=766&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=766&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=963&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=963&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443767/original/file-20220201-26-1ob6gb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=963&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Economic vulnerability to erosion of selected ‘hotspots’.</span>
<span class="attribution"><span class="source">Komali Kantamaneni</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Sites such as <a href="https://www.confused.com/home-insurance/living-on-the-edge">Hornsea, Camber Sands, Sunderland, Bognor and Withernsea</a> have already lost several hundred meters of coastline, and much of their coastline will crumble into the sea in the next 20 years.</p>
<p>There is, of course, still significant uncertainty about how vulnerable different stretches of the coastline are to erosion. Differing geologies, coastal defences, wave properties and weather make every site respond differently to the effects of climate and land-use change. </p>
<p>Regions vulnerable to erosion need to take steps to reduce the impact of associated hazards like flooding or landslides. Interventions need to be sympathetic to the needs of locals, those down coast and the environment. If we fail to do this, we will encounter ever-increasing societal costs and environmental destruction.</p><img src="https://counter.theconversation.com/content/175508/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Komali Kantamaneni receives funding from British Council and Newton Fund. </span></em></p><p class="fine-print"><em><span><a href="mailto:andr3@bgs.ac.uk">andr3@bgs.ac.uk</a> receives grant funding from UK Research and Innovation, the Natural Environment Research Council and the British Council. </span></em></p><p class="fine-print"><em><span>Luiza C Campos receives funding from the UK Space Agency, Innovate UK, UCL Grand Challenges, and UCL Health of the Public.</span></em></p>Around 17% of the mainland coastline is affected.Komali Kantamaneni, Senior Research Fellow, Faculty of Science and Technology, University of Central LancashireAndrew Barkwith, Principal Numerical Modeller, British Geological SurveyLuiza C Campos, Associate Professor of Environmental Engineering, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1718352021-12-01T13:31:40Z2021-12-01T13:31:40ZAfrica’s growing road network may affect ecosystems: we reviewed the evidence<figure><img src="https://images.theconversation.com/files/434161/original/file-20211126-23-ufi94k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The road leading to the Etosha National Park East Gate at Fort Namutoni, Etosha National Park, Namibia.</span> <span class="attribution"><span class="source">Getty Images/ Alexander Hafemann</span></span></figcaption></figure><p>The mission to <a href="https://au.int/en/agenda2063/overview">integrate African economies</a> relies on the development and construction of major <a href="https://www.afdb.org/en/documents/document/cross-border-road-corridors-109949">infrastructure</a>, from roads to railways and ports across the continent. For instance, the 1,900km Nacala corridor aims to connect the landlocked regions of Zambia and Malawi, as well as the interior of Mozambique, to the Nacala port on the Indian Ocean. </p>
<p>Many researchers <a href="https://www.nature.com/articles/nature13717">claim</a> these large-scale road developments will have detrimental impacts on natural ecosystems. They are concerned about a reduction in habitat availability and connectivity. Roads can also lead to changes in land use, create illegal access into previously inaccessible areas, and result in conflict between people and wildlife.</p>
<p>Despite concern and speculation about the environmental impacts of future road development in Africa, there has up to now been very little systematic evaluation of evidence of these impacts.<br>
We decided to fill this gap. In a <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2ad9">systematic review</a> of existing literature, we extracted and synthesised information on about 270 reported effects of roads on ecosystems. We also identified underlying mechanisms inside and outside protected areas in different sub-regions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map with lines" src="https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=510&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=510&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=510&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=640&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=640&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433968/original/file-20211125-25-1vfzi2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=640&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Nacala Corridor is one of 17 major corridors proposed for development across the African continent. It’s one of several corridors proposed to connect East and Southern African countries and will be 1900km long, 971km of which is for road infrastructure. The colour associated with the road corridor (line segment) describes how the road was financed.</span>
<span class="attribution"><span class="source">African Development Bank 2019</span></span>
</figcaption>
</figure>
<p>This helped us build a greater understanding of road impacts in sub-Saharan Africa, as well as the conditions under which future roads might pose a significant threat.</p>
<h2>The impacts of roads</h2>
<p>We found the reported effects of roads were usually related to land cover (change in type or degradation) and biodiversity (impacts on species composition or distribution). </p>
<p>Our findings suggest that the presence of roads, even inside protected areas, may pose a significant threat to species. The interactions between roads and species were not the same in all regions. Roads in and around protected areas had more negative impacts in central Africa than in southern Africa.</p>
<p>In many instances, roads were associated with a decrease in animal abundance. The main reasons were that roads were a barrier to the <a href="https://theconversation.com/kenyas-huge-railway-project-is-causing-environmental-damage-heres-how-159813">movement of animals</a>, and they gave hunters and poachers access to previously unreachable habitats. Some road systems restricted the distribution range of animals. </p>
<p>But not all species responded in the same way. Some animals – like gorillas, bovids, carnivores and sometimes elephants – did not always avoid areas close to roads. Instead, they used roads as corridors for movement or even as foraging sites. In most published studies in our review, however, these mechanisms were usually speculated and required additional rigorous long-term studies for validation.</p>
<p>The review showed that roads, especially major ones, also had a strong influence on land use patterns. When roads created connections to previously inaccessible land, markets, cities and economic opportunities, they stimulated activities such as agriculture and logging. Roads also increased land degradation in many areas, often triggering erosion and soil loss.</p>
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Read more:
<a href="https://theconversation.com/nairobis-new-expressway-may-ease-traffic-woes-but-mostly-for-the-wealthy-170164">Nairobi's new expressway may ease traffic woes – but mostly for the wealthy</a>
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<h2>What to expect</h2>
<p>Our review revealed that the road-effect zone was typically between 1km and 7km for larger mammals. Animals in these zones may be forced to restrict their movement and thus reduce their home range size.</p>
<p>Future road development will most likely promote landscape transformation processes as far as 10km away from roads. Secondary road effects (such as further road development), as seen in the <a href="https://pubmed.ncbi.nlm.nih.gov/19748151/">Amazon</a>, can extend far deeper into core natural habitats. Road development may promote local economic activities and transitions from farmland to built-up areas. Cropland expansion can be expected around major roads that provide access to markets. New roads may increase logging, causing substantial deforestation and a change of land use to large scale agriculture.</p>
<p>If not constructed and managed carefully, roads may lead to erosion, soil loss and flooding in many areas. </p>
<h2>Addressing the impacts of roads</h2>
<p>Where the potential impacts of future road development have not been considered and development has already started or completed, it may be late for conservation efforts in some areas, especially if formal protection status is not allocated fast enough.</p>
<p>Intervention at the design and construction phases of road development is critical for mitigating many of the effects we found in this study. Early phases should identify alternative routes to avoid areas of high ecological value. Given the size of the transportation network envisaged for the African continent, our study calls for a pan-African response. </p>
<p>When road development cannot be avoided in ecologically sensitive areas, effective mitigation strategies need to be developed. Conservation planners and environmental impact assessment practitioners play a vital role in this process. </p>
<p>There are some well researched measures to be found in the <a href="https://onlinelibrary.wiley.com/doi/book/10.1002/9781118568170">Handbook for Road Ecology</a>. Other complex effects (such as illegal hunting and harvesting or land use changes) are often unintended consequences of roads and more difficult to address. They may depend on law enforcement and policy.</p>
<p>If the past is an indication of the future, new road development will have a strong influence on species distribution and land cover patterns in sub-Saharan Africa. Identifying how these impacts develop allows planners to better predict where and under what conditions roads might be a serious problem for different species and ecosystems more broadly.</p><img src="https://counter.theconversation.com/content/171835/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lavinia Perumal received funding from the National Research Foundation (NRF), Austrian Federal Ministry of Education, Science and Research (BMBWF) and the South African Department of Science and Technology (DST) . </span></em></p><p class="fine-print"><em><span>Mark New receives funding from a number of national and international research funders, including the South African National Research Foundation, the International Development Research Centre, UK Research and Innovation, the AXA Research Fund and the BNP-Paribas Foundation. The research described in this article was supported by NRF and BMBWF.</span></em></p><p class="fine-print"><em><span>Wei Liu received funding from Austrian Federal Ministry of Education, Science and Research (BMBWF).</span></em></p><p class="fine-print"><em><span>Matthias Jonas does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The presence of roads, even inside protected areas, may pose a significant threat to species.Lavinia Perumal, PhD candidate Department of Environmental & Geographical Science, University of Cape TownMark New, Director, African Climate and Development Initiative, University of Cape TownMatthias Jonas, Senior Research Scholar Exploratory Modeling of Human-natural Systems Research Group - Advancing Systems Analysis Program, International Institute for Applied Systems Analysis (IIASA)Wei Liu, Guest Research Scholar, International Institute for Applied Systems Analysis (IIASA)Licensed as Creative Commons – attribution, no derivatives.