tag:theconversation.com,2011:/uk/topics/vegetation-2636/articlesVegetation – The Conversation2023-11-17T20:56:02Ztag:theconversation.com,2011:article/2177862023-11-17T20:56:02Z2023-11-17T20:56:02ZPlants are likely to absorb more CO₂ in a changing climate than we thought – here’s why<figure><img src="https://images.theconversation.com/files/560095/original/file-20231116-23-ylmksg.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4493%2C2991&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aerial-top-view-forest-tree-rainforest-2033096327">Olga Danylenko/Shutterstock</a></span></figcaption></figure><p>The world’s vegetation has a remarkable ability to absorb carbon dioxide (CO₂) from the air and store it as biomass. In doing so, plants slow down climate change since the CO₂ they take up does not contribute to global warming. </p>
<p>But what will happen under more advanced climate change? How will vegetation respond to projected changes in atmospheric CO₂, temperatures and rainfall? Our <a href="http://www.science.org/doi/10.1126/sciadv.adh9444">study</a>, published today in Science Advances, shows plants might take up more CO₂ than previously thought. </p>
<p>We found climate modelling that best accounted for the processes that sustain plant life consistently predicted the strongest CO₂ uptake. The most complex model predicted up to 20% more than the simplest version. </p>
<p>Our findings highlight the resilience of plants, and the importance of planting trees and preserving existing vegetation to slow climate change. While this is good news, it doesn’t let us off the hook in the fight against climate change. The rapid increase in atmospheric CO₂ means we must still cut emissions.</p>
<figure class="align-center ">
<img alt="A person holds a small sapling ready to be planted in the soli with a spade and trees in the background" src="https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560100/original/file-20231117-17-cjovq1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mass tree planting can help slow climate change but won’t on its own keep warming within acceptable limits.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/new-life-81582967">EduardSV/Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/carbon-budget-for-1-5-c-will-run-out-in-six-years-at-current-emissions-levels-new-research-216459">Carbon budget for 1.5°C will run out in six years at current emissions levels – new research</a>
</strong>
</em>
</p>
<hr>
<h2>What happens to the CO₂ plants take up?</h2>
<p>Plants take up CO₂ through photosynthesis. This process uses the Sun’s energy to convert – or “fix” – CO₂ from the air into the sugars plants use for growth and metabolic activity. </p>
<p>Plants release around half of that CO₂ back to the atmosphere via respiration relatively quickly. The other half is used for growth and stays in the plant biomass for longer – months to centuries. </p>
<p>That biomass will eventually die and decompose. Part of the carbon will be released again to the atmosphere, but other parts will enter the soil where it can stay for hundreds of years. </p>
<p>So, if plants take up more CO₂, it’s likely more carbon will be stored in vegetation and soils. This “land sink” of carbon has indeed increased over the past few decades as the <a href="https://essd.copernicus.org/articles/14/4811/2022/">annual global carbon budget assessment</a> has shown. </p>
<p>What’s more, the increasing land carbon sink has largely been attributed to the <a href="https://www.pnas.org/doi/10.1073/pnas.1407302112">beneficial effects of rising atmospheric CO₂ on plant photosynthesis</a>. This is important because that carbon stored in plants and soils slows the increase in atmospheric CO₂ and therefore global warming. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three line graphs showing the rate of increase in atmospheric CO2 and the extent of the land sink and ocean sink" src="https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=223&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=223&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=223&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=280&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=280&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560090/original/file-20231116-21-zi2n16.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=280&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Main components of the global carbon cycle, showing the rate of increase in atmospheric CO₂ and the extent of the land sink and ocean sink.</span>
<span class="attribution"><a class="source" href="https://www.globalcarbonproject.org/carbonbudget/">Global Carbon Project 2022</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/in-20-years-of-studying-how-ecosystems-absorb-carbon-heres-why-were-worried-about-a-tipping-point-of-collapse-179554">In 20 years of studying how ecosystems absorb carbon, here's why we're worried about a tipping point of collapse</a>
</strong>
</em>
</p>
<hr>
<h2>A gap in current climate models</h2>
<p>But how do we know how much carbon is taken up and stored on land? Even more challenging, how can we predict what happens in the future? </p>
<p>One attempt to answer these questions is to use so-called terrestrial biosphere models. These models encapsulate our understanding of how plants function and how they respond to changes in climate. </p>
<p>For example, we know from experiments that plants <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3040.2007.01641.x">photosynthesise more under higher CO₂ concentrations</a> but <a href="https://academic.oup.com/jxb/article/62/3/869/478813">less when they don’t have enough water</a>. Models translate all this knowledge into mathematical equations and allow them to interact with each other. </p>
<p><em>All</em> this knowledge? Well, not really, and that was the motivation for our research. While today’s terrestrial biosphere models include <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001453">a plethora of processes</a>, they do not necessarily account for all mechanisms and processes that we know exist. There might not be enough data or information available to confidently represent a process across the entire globe, or it might just be difficult – conceptually or technically – to include it in models. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1359095003763589122"}"></div></p>
<h2>What did the study look at?</h2>
<p>We included three of those neglected processes into the well-established <a href="https://gmd.copernicus.org/articles/11/2995/2018/">Australian terrestrial biosphere model</a>. We accounted for:</p>
<ol>
<li>how efficiently CO₂ can move inside the leaf</li>
<li>how plants adjust to changes in their surrounding temperature</li>
<li>how they distribute nutrients most economically. </li>
</ol>
<p>We used the most recent data and research publications to include the processes as realistically as possible. We then confronted the model with a <a href="https://www.carbonbrief.org/explainer-the-high-emissions-rcp8-5-global-warming-scenario/">strong climate change scenario</a> and looked at how much CO₂ plants will take up until the end of this century. </p>
<p>We repeated this experiment with eight different versions of the model. The simplest version did not account for any of the three physiological mechanisms. The most complex version accounted for all three. </p>
<p>The results were surprisingly clear: the more complex the model, the higher the predicted CO₂ uptake by plants. Model versions that accounted for at least two mechanisms (those with greater ecological realism) consistently predicted the strongest CO₂ uptake – up to 20% more than the simplest version. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/no-more-excuses-restoring-nature-is-not-a-silver-bullet-for-global-warming-we-must-cut-emissions-outright-186048">No more excuses: restoring nature is not a silver bullet for global warming, we must cut emissions outright</a>
</strong>
</em>
</p>
<hr>
<h2>What does this mean for climate action?</h2>
<p>For modellers this is important news. It tells us our current models, which are usually at the lower end of this complexity range, likely underestimate future CO₂ uptake by plants.</p>
<p>These results suggest plants could be pretty resilient to even severe climate change. </p>
<p>However, we only looked at this from a plant physiological angle. Other processes in models are still oversimplified, such as the impacts of, and recovery from, fires and droughts. We clearly need to better capture these processes to get a more complete picture of how effectively plants will absorb CO₂ in the future. </p>
<p>And last but not least, because plants help fight climate change, it’s essential to conserve existing plant biomass and restore lost vegetation. </p>
<p>But while plants might even be more industrious helpers than previously assumed, they will never do the heavy lifting for us. It is still up to us humans to fight climate change by drastically cutting fossil fuel emissions. There is no shortcut.</p><img src="https://counter.theconversation.com/content/217786/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jürgen Knauer 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>Climate modelling that best accounts for the processes that sustain plant life predicts plants could absorb up to 20% more CO₂ than the simplest version predicted.Jürgen Knauer, Postdoctoral Research Fellow, Hawkesbury Institute for the Environment, Western Sydney UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2135902023-10-25T10:49:23Z2023-10-25T10:49:23ZHow climate change is affecting the seasons<figure><img src="https://images.theconversation.com/files/555566/original/file-20231024-29-a074ma.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C3686%2C3637&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/beautiful-autumnal-scenery-tree-tunnel-regents-747085630">I Wei Huang/Shutterstock</a></span></figcaption></figure><p>Autumn has finally arrived in the UK following an <a href="https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2023/2023_05_september_heatwave.pdf">unusually sunny September</a>. The days are growing shorter, the temperature cooler, and the leaves are changing colour. </p>
<p>The delayed onset of autumn in 2023 is not a one off. It’s actually part of a broader trend in which the shift from summer to winter is happening later in the year. My <a href="https://www.researchgate.net/publication/259844410_C_Jeganathan_J_Dash_and_PM_Atkinson_2014_Remotely_sensed_trends_in_the_phenology_of_northern_high_latitude_terrestrial_vegetation_controlling_for_land_cover_change_and_vegetation_type_Remote_Sensing_o">own research</a> that I’ve carried out over the past 13 years points towards climate change as the likely culprit.</p>
<p>One of the most noticeable effects of climate change is the changing patterns of vegetation seasonality around us. This includes the timing of important biological events such as bud burst, the appearance of the first leaves, flowering and leaf fall.</p>
<p>In general, the appearance of the first leaf marks the arrival of spring, while leaf fall signals the beginning of autumn. The timing of these events is changing, particularly in the northern hemisphere, where spring appears to be starting earlier and autumn’s onset is being delayed.</p>
<p>Traditionally, monitoring vegetation seasonality involved meticulously documenting these seasonal events year after year. The earliest records of spring events in the UK date back to 1736, when naturalist <a href="https://www.britannica.com/science/phenology#:%7E:text=Robert%20Marsham%E2%80%99s%20observations">Robert Marsham</a> began recording the timing of spring events in Norwich, England. </p>
<p>Today, satellite data has become an essential tool for tracking changes in vegetation seasonality. This data can be used to estimate vegetation vigour (an indicator of vegetation’s condition, strength and lushness). Changes can then be used to identify the start and end of each growing season.</p>
<h2>Longer growing seasons</h2>
<p>Climate researchers now have nearly five decades of satellite observations at their disposal. Analysis of this data reveals that spring has advanced by approximately 15 days, while autumn has been delayed by a similar amount. The overall outcome has been the extension of the growing season by an entire month over the past three decades.</p>
<p>The shift in the timing of the seasons is particularly pronounced at higher latitudes. Vegetation situated more than 55° north of the equator, such as in the larch forests of northern Russia, has shown a trend towards an extended growing season, increasing by up to one day per year.</p>
<p>A longer growing season is not necessarily a bad thing. It means a longer period of photosynthesis, which theoretically could boost <a href="https://www.britannica.com/technology/carbon-sequestration">net carbon uptake</a> – although there is <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022JG006900">no concrete evidence</a> for this yet.</p>
<p>But an earlier onset of the growing season exposes plants to the risk of damage from spring frosts and an increased vulnerability to summer drought. <a href="https://www.science.org/doi/10.1126/sciadv.aba2724">Research</a> has found that an early spring in central and northern Europe in 2018 promoted increased vegetation growth. This, in turn, contributed to soil losing its moisture quickly, amplifying summer drought conditions.</p>
<figure class="align-center ">
<img alt="A view of a coniferous forest with a sea bay and hills in the distance." src="https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/555571/original/file-20231024-29-9r2jaf.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 shift in the timing of the seasons is particularly pronounced at higher latitudes.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/beautiful-autumn-landscape-view-larch-trees-2207472441">Andrei Stepanov/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Role of climate change</h2>
<p>Temperature is <a href="https://www.nature.com/articles/nclimate3277">one of the primary factors</a> influencing vegetation growth at high northerly latitudes. So, an earlier onset of spring and a later arrival of autumn are probably driven by the rising global mean temperature. Since 1981, the global mean temperature has increased by <a href="https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202213">0.18°C per decade</a>.</p>
<p>Nonetheless, the influence of temperature on the duration of the growing season may change depending on the type of vegetation. In ecosystems primarily dominated by forests, a warmer climate <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022JG006900">can lead to</a> more photosynthesis and increased vegetation productivity. </p>
<p>On the other hand, in a warmer climate, more water evaporates from the Earth’s surface, drying out the soil. This could adversely affect the growth of plants with shallow roots, such as grasses and herbaceous plants.</p>
<p>Another consequence of climate change is the increased frequency of droughts during the peak of the growing season. Drought conditions result in severe water stress for plants, leading to the premature shedding of leaves or a change in their colour, a phenomenon often referred to as a “false autumn”. </p>
<p>The UK <a href="https://www.bbc.co.uk/news/science-environment-62582186">experienced such conditions</a> in August 2022, when there was an early leaf fall and the browning of leaves, as the country grappled with an <a href="https://www.reuters.com/world/uk/extreme-weather-warning-force-britain-new-heatwave-hits-2022-08-11/">extreme heatwave</a>.</p>
<p>A longer and drier growing season can also increase the risk of forest fires. A <a href="https://www.science.org/doi/10.1126/science.1128834">US study</a> from 2006 revealed a significant surge in wildfire activity within the forests of the northern Rockies from the mid-1980s. This change was closely linked to increased spring and summer temperatures and an earlier spring snowmelt.</p>
<figure class="align-center ">
<img alt="Yellow and orange maple leaves on the ground in the sunlight." src="https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/555574/original/file-20231024-21-pk0kuk.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">Trees sometimes shed their leaves early when under stress.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/yellow-orange-maple-leaves-forest-on-1988839673">MVolodymyr/Shutterstock</a></span>
</figcaption>
</figure>
<p>Climate change is having a clear impact on vegetation growth and seasonality. But the extent and severity of its impact varies depending on the type of plant and where it grows.</p>
<p>The availability of satellite data spanning the past 50 years is a valuable resource for capturing changes in the duration of the vegetation growing season. This data is helping scientists quantify the scale and consequences of these changes, providing insights into how plants are responding to our warming climate.</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>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 20,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/213590/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jadu Dash 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>Autumn is arriving later in the year – climate change is probably to blame.Jadu Dash, Professor of Remote Sensing in Geography and Environmental Science, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2117122023-08-17T19:42:11Z2023-08-17T19:42:11ZA changing climate, growing human populations and widespread fires contributed to the last major extinction event − can we prevent another?<p>Over the past decade, deadly wildfires have become increasingly common because of both <a href="https://www.scientificamerican.com/article/climate-change-is-escalating-californias-wildfires/">human-caused climate change</a> and <a href="https://www.nytimes.com/2023/08/13/us/hawaii-wildfire-factors.html">disruptive land management practices</a>. Southern California, where the three of us live and work, has been <a href="https://ktla.com/news/the-cities-where-wildfires-threaten-the-most-homes-in-california/">hit especially hard</a>.</p>
<p>Southern California also experienced a wave of wildfires 13,000 years ago. These fires permanently transformed the region’s vegetation and <a href="https://www.science.org/doi/10.1126/science.abo3594">contributed to Earth’s largest extinction</a> in more than 60 million years.</p>
<p>As <a href="https://www.ioes.ucla.edu/person/emily-lindsey/">paleontologists</a>, <a href="https://nhm.org/person/dunn-regan">we have</a> a <a href="https://scholar.google.com/citations?user=_FveDz4AAAAJ&hl=en">unique perspective</a> on the long-term causes and consequences of environmental changes, both those linked to natural climate fluctuations and those wrought by humans. </p>
<p><a href="https://www.science.org/doi/10.1126/science.abo3594">In a new study</a>, published in August 2023, we sought to understand changes that were happening in California during the last major extinction event at the <a href="https://www.britannica.com/science/Pleistocene-Epoch">end of the Pleistocene</a>, a time period known as the Ice Age. This event wiped out <a href="https://www.smithsonianmag.com/science-nature/what-happened-worlds-most-enormous-animals-180964255/">most of Earth’s large mammals</a> between about 10,000 and 50,000 years ago. This was a time marked by dramatic climate upheavals and rapidly spreading human populations. </p>
<h2>The last major extinction</h2>
<p>Scientists often call the past 66 million years of Earth’s history the Age of Mammals. During this time, our furry relatives took advantage of the <a href="https://www.nhm.ac.uk/discover/how-an-asteroid-caused-extinction-of-dinosaurs.html">extinction of the dinosaurs</a> to become the dominant animals on the planet. </p>
<p>During the Pleistocene, Eurasia and the Americas teemed with enormous beasts like woolly mammoths, giant bears and dire wolves. Two species of camels, three species of ground sloths and five species of large cats <a href="https://tarpits.org/research-collections/tar-pits-collections/mammal-collections">roamed what is now Los Angeles</a>.</p>
<p>Then, abruptly, they were gone. All over the world, the large mammals that had characterized global ecosystems for tens of millions of years disappeared. North America <a href="https://www.doi.org/10.1146/annurev.ecolsys.34.011802.132415">lost more than 70%</a> of mammals weighing more than 97 pounds (44 kilograms). South America lost more than 80%, Australia nearly 90%. Only Africa, Antarctica and a few remote islands retain what could be considered “natural” animal communities today.</p>
<p>The reason for these extinctions remains obscure. For decades, paleontologists and archaeologists have debated potential causes. What has befuddled scientists is not that there are no obvious culprits but that there are too many. </p>
<p>As the last ice age ended, a warming climate led to altered weather patterns and the reorganization of <a href="https://doi.org/10.1016/j.quascirev.2015.08.029">plant communities</a>. At the same time, human populations were rapidly increasing and <a href="https://www.worldhistory.org/article/1070/early-human-migration/">spreading around the globe</a>. </p>
<p>Either or both of these processes could be implicated in the extinction event. But the fossil record of any region is usually too sparse to know exactly when large mammal species disappeared from different regions. This makes it difficult to determine whether habitat loss, resource scarcity, natural disasters, human hunting or some combination of these factors is to blame.</p>
<h2>A deadly combination</h2>
<p>Some records offer clues. <a href="https://tarpits.org/">La Brea Tar Pits</a> in Los Angeles, the world’s richest ice age fossil site, preserves the bones of thousands of large mammals that were trapped in viscous asphalt seeps <a href="https://resolver.caltech.edu/CaltechAUTHORS:20191203-160736818">over the past 60,000 years</a>. Proteins in these bones can be precisely dated <a href="https://doi.org/10.1016/j.quageo.2014.03.002">using radioactive carbon</a>, giving scientists unprecedented insight into an ancient ecosystem and an opportunity to illuminate the timing – and causes – of its collapse. </p>
<p>Our recent study from La Brea Tar Pits and <a href="https://en.wikipedia.org/wiki/Lake_Elsinore">nearby Lake Elsinore</a> has unearthed evidence of a dramatic event 13,000 years ago that permanently transformed Southern California’s vegetation and <a href="https://www.science.org/doi/10.1126/science.abo3594">caused the disappearance</a> of La Brea’s iconic mega-mammals. </p>
<p>Sediment archives from the lake’s bottom and archaeological records provide evidence of a deadly combination – a warming climate <a href="https://doi.org/10.1002/jqs.3018">punctuated by decadeslong droughts</a> and rapidly rising human populations. These factors pushed the Southern California ecosystem to a tipping point. </p>
<p><a href="https://www.doi.org/10.1126/sciadv.1501682">Similar combinations</a> of climate warming and human impacts have been blamed for ice age extinctions elsewhere, but our study found something new. The catalyst for this dramatic transformation seems to have been an unprecedented increase in wildfires, which were probably set by humans. </p>
<p>The processes that led to this collapse are familiar today. As California warmed coming out of the last ice age, the landscape became drier and forests receded. At La Brea, herbivore populations declined, probably from a combination of human hunting and habitat loss. Species associated with trees, like camels, disappeared entirely. </p>
<p>In the millennium leading up to the extinction, mean annual temperatures in the region <a href="https://doi.org/10.1016/j.epsl.2019.03.024">rose 10 degrees Farenheit</a> (5.5 degrees Celsius), and the lake began evaporating. Then, 13,200 years ago, the ecosystem entered a 200-year-long drought. Half of the remaining trees died. With fewer large herbivores to eat it, dead vegetation built up on the landscape. </p>
<p>At the same time, human populations began expanding across North America. And as they spread, people brought with them a powerful new tool – fire. </p>
<p>Humans and our ancestors have used fire for <a href="https://www.science.org/content/article/artificial-intelligence-may-have-unearthed-one-world-s-oldest-campfires">hundreds of thousands of years</a>, but fire has <a href="https://www.firescience.gov/projects/09-2-01-9/supdocs/09-2-01-9_Chapter_3_Fire_Regimes.pdf">different impacts in different ecosystems</a>. Charcoal records from Lake Elsinore reveal that before humans, fire activity was low in coastal Southern California. But 13,200 to 13,000 years ago, as human populations grew, fire in the region increased by an order of magnitude. </p>
<p>Our research suggests that the combination of heat, drought, herbivore loss and human-set fires had pushed this system to a <a href="https://www.nature.com/articles/nature11018">tipping point</a>. At the end of this period, Southern California was covered in chaparral plants, which thrive after fires. A new fire regime had become established, and the iconic La Brea megafauna had disappeared.</p>
<h2>Lessons for the future</h2>
<p>Studying the causes and consequences of the Pleistocene extinctions in California can provide valuable context for understanding today’s climate and biodiversity crises. A similar combination of climate warming, expanding human populations, biodiversity loss and human-ignited fires that characterized the ice age extinction interval in Southern California are <a href="https://www.doi.org/10.1126/science.abb0355">playing out again today</a>.</p>
<p>The alarming difference is that temperatures today are rising <a href="https://www.scientificamerican.com/article/todays-climate-change-proves-much-faster-than-changes-in-past-65-million-years/">10 times faster</a> than they did at the end of the ice age, primarily because of the burning of fossil fuels. This human-caused climate change has contributed to a fivefold increase in fire frequency and intensity and the amount of area burned in the state of California in the <a href="https://doi.org/10.1029/2019EF001210">past 45 years</a>. </p>
<p>While California is now <a href="https://earthobservatory.nasa.gov/images/148908/whats-behind-californias-surge-of-large-fires">famous for extreme fires</a>, our study reveals that fire is a relatively new phenomenon in this region. In the 20,000 years leading up to the extinction, the Lake Elsinore record shows very low incidence of any fire even during comparable periods of drought. Only after human arrival does fire become a regular part of the ecosystem. </p>
<p>Even today, <a href="https://www.businessinsider.com/pge-caused-california-wildfires-safety-measures-2019-10">downed power lines</a>, campfires and <a href="https://www.nytimes.com/2020/09/07/us/gender-reveal-party-wildfire.html">other human activities</a> start <a href="https://doi.org/10.1071/WF18026">over 90%</a> of wildfires in coastal California. </p>
<p>The parallels between the late Pleistocene megafaunal extinctions and today’s environmental crises are striking. The past teaches us that the ecosystems we depend upon are vulnerable to collapse when stressed by multiple intersecting pressures. Redoubling efforts to eliminate greenhouse gas emissions, prevent reckless fire ignitions and preserve Earth’s remaining megafauna can help avert another, even more catastrophic transformation.</p><img src="https://counter.theconversation.com/content/211712/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emily Lindsey receives funding from the National Science Foundation, which funded some of the research reported in this article. </span></em></p><p class="fine-print"><em><span>Lisa N. Martinez receives funding from the National Science Foundation and the UCLA Endowed Chair in Geography of California and the American West. </span></em></p><p class="fine-print"><em><span>Regan E. Dunn receives funding from National Science Foundation and NASA. </span></em></p>New findings from the La Brea Tar Pits in southern California suggest human-caused wildfires in the region, along with a warming climate, led to the loss of most of the area’s large mammals.Emily Lindsey, Associate Curator, La Brea Tar Pits; Adjunct Faculty, Institute of the Environment and Sustainability, UCLA, University of California, Los AngelesLisa N. Martinez, Ph.D. Candidate in Geography, University of California, Los AngelesRegan E. Dunn, Adjunct Professor of Earth Sciences, USC Dornsife College of Letters, Arts and SciencesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2013632023-06-07T17:44:04Z2023-06-07T17:44:04ZThe invisible effects of human activity on nature<figure><img src="https://images.theconversation.com/files/515229/original/file-20230314-2080-67ctev.JPG?ixlib=rb-1.1.0&rect=27%2C0%2C4573%2C3414&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lake surrounding a mining site in Northern Québec.</span> <span class="attribution"><span class="source">(Maxime Thomas)</span></span></figcaption></figure><p>Discussions at the recent COP15 biodiversity conference in Montréal highlighted once again the <a href="https://www.unep.org/news-and-stories/story/cop15-ends-landmark-biodiversity-agreement">impact of human activities on wildlife</a>. Many species are <a href="https://doi.org/10.1016/j.scitotenv.2022.158038">forced to migrate</a>, <a href="https://www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/">are seeing their populations declining, or worse, are finding themselves on the brink of extinction</a>. For example, the populations of woodland caribou (<em>Rangifer tarandus</em>) are declining <a href="https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/caribou-specific-populations-2014/part-2.html">as a result of the damage of logging on their habitat</a>.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.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>
<p><strong>This article is part of <em>La Conversation Canada’s</em> series <a href="https://theconversation.com/ca-fr/topics/foret-boreale-138017">The boreal forest: A thousand secrets, a thousand dangers</a></strong></p>
<p><br><em>La Conversation Canada invites you to take a virtual walk in the heart of the boreal forest. In this series, our experts focus on management and sustainable development issues, natural disturbances, the ecology of terrestrial wildlife and aquatic ecosystems, northern agriculture and the cultural and economic importance of the boreal forest for Indigenous peoples. We hope you have a pleasant — and informative — walk through the forest!</em></p>
<hr>
<p>However, the consequences of human activities are not always visible. Before being driven into decline, <a href="https://doi.org/10.1111/j.1365-294X.2007.03484.x">some species are able to adapt to disturbances in their habitat</a> — but only up to a point. This is particularly true of plants, which cannot move to avoid disturbances in their environment, and as a result, are necessarily subjected to the impact of human activities. </p>
<p>Our work in forest ecology at the Université du Québec en Abitibi-Témiscamingue (UQAT) is allowing us to demonstrate the invisible effects of human activities on boreal flora. </p>
<h2>Adapting, but not without consequences…</h2>
<p>The capacity of plants to adapt is actually a double-edged sword. On the one hand, it makes it possible to put off a decline in their populations due to human activity. On the other hand, it can lead researchers to underestimate the consequences that human activities are having on the environment.</p>
<p>When a species adapts to disturbances in its habitat, its nutritional and medicinal properties may change. This is because plants respond to these disturbances by producing chemical compounds. <a href="https://www.canada.ca/en/health-canada/services/food-nutrition/reports-publications/food-safety/glycoalkaloids-foods.html">Some of these compounds can have harmful effects on the health of the humans who consume them</a>. In the boreal forest, this can take the form of toxins in the seeds of <a href="https://m.espacepourlavie.ca/en/biodome-flora/ground-hemlock">ground hemlock</a> and the leaves of <a href="https://espacepourlavie.ca/en/biodome-flora/sheep-laurel">sheep laurel</a>.</p>
<p><a href="https://doi.org/10.1016/j.jarmap.2018.11.004">However, other compounds are sought after for their benefits to human health</a>. For example, antioxidants, which are highly valued in food for their health benefits, have the primary function of <a href="https://doi.org/10.1007/978-981-10-5254-5_1">protecting plants from sunlight and various pollutants</a>. One example of these is <a href="http://www5.agr.gc.ca/resources/prod/doc/misb/fb-ba/nutra/pdf/polyphenols_eng.pdf">polyphenols, found in some boreal forest berries, such as blueberries and cranberries</a>.</p>
<h2>…especially for Indigenous communities</h2>
<p>People whose diet consists of wild plants are particularly affected by the changes in chemical composition that take place when plants are adapting to disturbances in their habitat. This is the case for Indigenous communities, who <a href="https://mackiki.uqat.ca/index.php">gather dozens of species in their traditional territories for food and medicinal purposes</a>.</p>
<p>To study how the adaptation of plants affects their chemical properties, we conducted a project in partnership with three Indigenous communities in northwestern Québec. Members of the communities suggested that we work on <a href="https://espacepourlavie.ca/en/biodome-flora/labrador-tea">Labrador tea</a> because of its cultural importance and medicinal uses. Labrador tea leaves are <a href="https://doi.org/10.1186/1746-4269-8-7">used in infusion to treat many ailments, such as osteoarthritis, diabetes or kidney problems</a>. <a href="https://doi.org/10.1016/j.jep.2015.12.021">The leaves contain antioxidants</a> called flavonoids in <a href="https://doi.org/10.1002/pca.1203">large quantities</a>.</p>
<figure class="align-center ">
<img alt="Labrador tea plants in the forest" src="https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508419/original/file-20230206-21-5q16bp.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">Labrador tea is an understory plant, 30 to 120 centimetres tall. It is found in moist forest environments in Canada and the northern United States.</span>
<span class="attribution"><span class="source">(Maxime Thomas), provided by the author</span></span>
</figcaption>
</figure>
<h2>Disturbances have different effects</h2>
<p>The members of the communities we met expressed their concerns about the consequences of two human disturbances on their territories: hydroelectric transmission lines and the exploitation of mining sites. The hydroelectric transmission lines create an artificial opening in the forest, which overexposes the plants to the sun. Mining sites <a href="https://doi.org/10.1007/s11157-017-9453-y">generate heavy metal pollution</a>. In both cases, <a href="https://doi.org/10.1155/2013/162750">Labrador tea plants adapt by producing flavonoids</a>.</p>
<figure class="align-center ">
<img alt="Labrador tea plants under a hydroelectric transmission line" src="https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508420/original/file-20230206-21-nh0rng.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">Plants under hydroelectric lines are much more exposed to the sun than in the surrounding forest.</span>
<span class="attribution"><span class="source">(Maxime Thomas), provided by the author</span></span>
</figcaption>
</figure>
<p>After analyzing the chemical composition of Labrador tea plants sampled from the territories of three Indigenous communities, we found contrasting effects of human disturbances. On the one hand, plants under hydroelectric transmission lines produced more flavonoids to protect themselves from the sun. On the other hand, plants near mining sites produced less flavonoids, due to a degradation of their metabolism by heavy metals.</p>
<p>However, before jumping to the conclusion that plants under hydroelectric transmission lines are healthier, other factors need to be considered. For example, chemicals potentially harmful to human health, such as <a href="https://doi.org/10.1093/annhyg/meh106">triclopyr</a> or <a href="https://www.cbc.ca/news/canada/new-brunswick/transmission-line-herbicide-1.3221418">glyphosate</a>, may be used to maintain hydroelectric transmission lines.</p>
<p>The flavonoid analysis only tells part of the story, so further analysis of factors such as the content of plant pollutants would be needed to gain a full picture of the effects of human disturbance on plant properties.</p>
<p>Biodiversity is important for the functioning of ecosystems, and also for the services it provides to humans. Indigenous peoples <a href="https://e360.yale.edu/features/native-knowledge-what-ecologists-are-learning-from-indigenous-people">have extensive knowledge of plants and their environment</a>, which should be valued. </p>
<p>Human disturbances affect the plants, the benefits they provide and the Indigenous knowledge that depends on them.</p><img src="https://counter.theconversation.com/content/201363/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Les auteurs ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'ont déclaré aucune autre affiliation que leur organisme de recherche.</span></em></p>Human activities can affect plants and have consequences for the human populations that consume them.Maxime Thomas, Doctorant en sciences de l'environnement, Université du Québec en Abitibi-Témiscamingue (UQAT)Hugo Asselin, Professeur titulaire, Université du Québec en Abitibi-Témiscamingue (UQAT)Mebarek Lamara, Professeur, Université du Québec en Abitibi-Témiscamingue (UQAT)Nicole Fenton, Professeure, écologie végétale/Professor, plant ecology, Université du Québec en Abitibi-Témiscamingue (UQAT)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2013652023-05-10T14:32:14Z2023-05-10T14:32:14ZForest fires: North America’s boreal forests are burning a lot, but less than 150 years ago<figure><img src="https://images.theconversation.com/files/514735/original/file-20230310-24-i3qohj.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C1637%2C748&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite image of a forest fire in July 2021 in northern Saskatchewan (Wapawekka Hills). The image covers an area of about 56 kilometres in width and is based on Copernicus Sentinel data.</span> <span class="attribution"><span class="source">(Pierre Markuse), CC BY 2.0</span></span></figcaption></figure><p>Unseasonably hot and dry weather conditions <a href="https://cwfis.cfs.nrcan.gc.ca/maps/fw?type=fdr&year=2023&month=5&day=5">in early May 2023</a> led to dozens of forest fires <a href="https://earthobservatory.nasa.gov/images/151313/fires-scorch-western-canada">in western Canada</a>. As of May 6, the Alberta government declared a <a href="https://edmonton.ctvnews.ca/alberta-declares-state-of-emergency-due-to-unprecedented-start-to-wildfire-season-1.6387641">state of emergency over wildfires</a>, and at the time of writing this article, <a href="https://www.cbc.ca/news/canada/edmonton/alberta-wildfires-environment-weather-extreme-1.6835352">nearly 30,000 people had to be evacuated</a>. Although it is too early to establish a precise assessment of this extreme episode, recent research allows us to place it in a broader context.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.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>
<p><strong>This article is part of <em>La Conversation Canada’s</em> series <a href="https://theconversation.com/ca-fr/topics/foret-boreale-138017">The boreal forest: A thousand secrets, a thousand dangers</a></strong></p>
<p><br><em>La Conversation Canada invites you to take a virtual walk in the heart of the boreal forest. In this series, our experts focus on management and sustainable development issues, natural disturbances, the ecology of terrestrial wildlife and aquatic ecosystems, northern agriculture and the cultural and economic importance of the boreal forest for Indigenous peoples. We hope you have a pleasant — and informative — walk through the forest!</em></p>
<hr>
<p>In North American boreal forests, several million hectares can go up in smoke in a single year. On the other hand, these forest fires can seem almost negligible for several consecutive years. During the past 60 years, <a href="https://doi.org/10.1139/cjfr-2018-0293">the area annually affected by forest fires has increased</a>, presumably because of climate change. Or at least that’s part of the explanation. </p>
<p>However, to better understand the long-term trends it is important to take a step back. This is the work our team of forest and fire ecology specialists recently carried out. </p>
<p><a href="https://doi.org/10.1071/WF22090">The results of our research</a> contradict the common wisdom about North American boreal forests — that they burned more in the past than they do today. But before we go into more detail about this, we feel it’s important to provide some background and context.</p>
<h2>What causes a forest fire?</h2>
<p>Scientists have been asking this question for a long time. Thanks to research carried out in the last few decades, the answer can now be summed up by three factors: vegetation, weather, and triggers.</p>
<p>Vegetation, which can be thought of as fuel, <a href="https://doi.org/10.1111/nph.12322">is a determining factor</a>. For example, large areas of dense coniferous forest are more likely to burn down than are deciduous forests with wetter undergrowth, or less dense forests. </p>
<p><a href="https://natural-resources.canada.ca/climate-change/impacts-adaptations/climate-change-impacts-forests/forest-change-indicators/fire-weather/17776">Meteorological factors also influence the flammability of fuels</a>; dry, windy conditions are highly conducive to the ignition and spread of fires. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?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">Burned forest landscape in 2010 in the Radisson region (northern Quebec).</span>
<span class="attribution"><span class="source">(Guillaume Avajon)</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>However, this combination of favourable conditions, itself, is not enough to generate a forest fire; there also needs to be a trigger. There are two types of triggers: lightning and humans. Although humans have been the cause of most fires started in recent decades in Canada, <a href="https://doi.org/10.1038/nclimate3329">lightning has actually been responsible for the largest area of burned forest</a>.</p>
<h2>Impacts on society</h2>
<p>When we hear about forest fires in the media, the news is usually tragic for communities. As a recent example, during the <a href="https://globalnews.ca/news/3138183/fort-mcmurray-wildfire-named-canadas-news-story-of-2016/">2016 Fort McMurray disaster</a>, some 600,000 hectares went up in smoke and over 88,000 people were evacuated. </p>
<p>Fires also have an economic impact on the forestry industry, as they consume millions of trees originally destined for mills. Moreover, fires accelerate climate change, as the burning of vegetation causes a massive release of CO2 into the atmosphere.</p>
<h2>A strong influence on ecosystems, but not necessarily negative</h2>
<p>The landscape we see a few weeks after a fire often looks apocalyptic. Forest fires leave significant traces on ecosystems and biodiversity. This is the case for certain species such as the Woodland Caribou, which depend on the presence of mature coniferous forests to survive. Fires <a href="https://doi.org/10.1016/j.gecco.2022.e02294">are therefore a threat to its survival</a>.</p>
<p>But, on the other hand, fires have always been part of forests, and are sometimes even essential to their ecological functioning. Most of the time, the burned landscape will gradually give way to vigorous young trees, which grow into a mature forest <a href="https://doi.org/10.1126/science.abf3903">in some 50 to 100 years</a>. Some tree species are even dependent on fire <a href="https://doi.org/10.1111/brv.12855">to regenerate and as a result, maintain themselves</a>. This is the case notably of <a href="https://doi.org/10.1139/x92-062">jack pine and black spruce</a>, which the forestry industry loves.</p>
<p>Many animal species are also fond of burned forests. Charred tree trunks provide food for <a href="https://doi.org/10.1071/WF08109">certain insect species</a>, such as the <a href="https://bugguide.net/node/view/573401/bgpage">black long-horned beetle</a>. Insects in turn provide abundant food for birds, like <a href="https://doi.org/10.1016/j.biocon.2009.01.022">black-backed woodpeckers</a>, which use snags (dead standing trees whose roots are still anchored to the ground) to nest.</p>
<p>In other words, fires are neither entirely good, nor entirely bad. It depends on your point of view. Additionally, as is often the case, it is also a question of balance…</p>
<h2>Reconstructing the history of fires over the last centuries</h2>
<p>Accurate records required to reconstruct the history of forest fires in Canada only go back to the 1960s. So how can we reconstruct the history of burned areas over the last few centuries? We can use the information contained in the trees themselves, and more specifically, their age. </p>
<p>In boreal forests, fire is a dominant natural disturbance. So, by determining the age of the oldest trees in a forest, provided these have not been cut down, <a href="https://doi.org/10.1078/1125-7865-00015">we can figure out the last time a forest burned</a>.</p>
<h2>A downward trend in burned areas over the past few centuries</h2>
<p>We gathered 16 studies that had independently applied the same method to different areas across North American boreal forests, from Alaska to Québec. After reanalysis of all this data in what scientists call a “meta-analysis,” <a href="https://doi.org/10.1071/WF22090%22%22">the results</a> are striking: North American boreal forests burned much more 150 years ago than they do today. In the earliest period covered by our data, between 1700 and 1850, the annual area burned was between two and more than 10 times greater than what has been observed over the past 40 years.</p>
<p>What explains this long-term downward trend? It is difficult to say based on the current state of research. Obviously, climate change is one of the suspects. The period from 1700 to 1850 was the end of what is known as the Little Ice Age, a period known for being colder, but probably also drier and, therefore, more conducive to fires. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map" src="https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=308&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=308&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=308&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=387&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=387&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=387&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mapping of fires (red on map) in North American boreal forests (green area on map) since 1960. The graph on the left shows the total area burned per year in millions of hectares. Over this recent period, there is both a large variability from year to year, and also a slight upward trend. Infographic by Victor Danneyrolles based on https://cwfis.cfs.nrcan.gc.ca/ha/nfdb for Canada and https://fire.ak.blm.gov for Alaska.</span>
<span class="attribution"><span class="source">(Victor Danneyrolles)</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>The vegetation could also have changed and become less flammable, particularly as a result of cuts by the logging industry over the 20th century. Also during the 20th century the technological and financial means allocated to firefighting continued to increase, culminating in the 1970s with the appearance of <a href="https://simpleflying.com/canadair-cl-215-scooper-history/">water bomber aircraft</a>. Fire suppression policies could therefore have also played a role in reducing fires in some areas. </p>
<p>However, fires began to decline as early as the 19th century, long before human communities had a significant impact on the North American boreal forest environment. It seems more likely that climate change is the primary cause of the decrease in fires, superimposed by the impacts of human activity.</p>
<p>We hope new research will soon allow us to answer these questions. A better understanding of why fires have decreased or increased over the past few centuries will give us a head start in predicting what to expect from future climate change.</p><img src="https://counter.theconversation.com/content/201365/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Raphaël Chavardès has received funding from Fonds de recherche du Québec - Nature et technologie (FRQNT).</span></em></p><p class="fine-print"><em><span>Yves Bergeron has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and Fonds de recherche du Québec - Nature et technologie (FRQNT).</span></em></p><p class="fine-print"><em><span>Victor Danneyrolles 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>North America’s boreal forests have been burning a lot, probably more and more over the past 60 years. Yet the long-term trend indicates that they are burning less than they were 150 years ago.Victor Danneyrolles, Professeur-chercheur en écologie forestière, Université du Québec à Chicoutimi (UQAC)Raphaël Chavardès, Postdoctoral fellow, Université du Québec en Abitibi-Témiscamingue (UQAT)Yves Bergeron, Professeur écologie et aménagement forestier, Université du Québec en Abitibi-Témiscamingue (UQAT)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1963982023-01-25T11:39:11Z2023-01-25T11:39:11ZLarge mammals shaped the evolution of humans: here’s why it happened in Africa<p>That humans originated in Africa is <a href="https://www.sciencedaily.com/releases/2007/05/070509161829.htm">widely accepted</a>. But it’s not generally recognised how unique features of Africa’s ecology were responsible for the crucial evolutionary transitions from forest-inhabiting fruit-eater to savanna-dwelling hunter. These were founded on earth movements and aided physically by Africa’s seasonal aridity, bedrock-derived soils and absence of barriers to movements between north and south. </p>
<p>These features promoted extensive savanna grasslands marked by erratic rainfall, regular fires and abundant numbers of diverse grazing and browsing animals. </p>
<p>My lifelong studies have focused on the ecology of Africa’s large herbivores and their effects on savanna vegetation. In my <a href="https://www.cambridge.org/za/academic/subjects/life-sciences/evolutionary-biology/only-africa-ecology-human-evolution">recent book</a>, by linking pre-existing threads together for the first time, I explain how distinctive features of these animals’ ecology, founded on Africa’s physical geography, enabled the adaptive changes that led ultimately to modern humans.</p>
<p>What emerges is the realisation that this amazing evolutionary transformation could only have occurred in Africa. This recognition emphasises the deep cultural legacy formed by Africa’s large mammal heritage for all of humankind.</p>
<h2>Ape-men</h2>
<p>Starting during the late Miocene, around 10 million years ago, a plume of molten magma, hot liquid material from deep inside the Earth, pushed eastern parts of Africa upward. This led to rifting of the Earth’s crust, volcanic eruptions and soils enriched in mineral nutrients from the lava and ash. Grassy savannas spread and animals adapted increasingly to graze this vegetation component. Apes from that time were forced to spend less time up in trees and more time walking upright on two legs. </p>
<p>Progressive reductions in rainfall, restricting plant growth and worsening dry season aridity, forced the early ape-men, (<a href="https://www.nature.com/scitable/knowledge/library/australopithecus-and-kin-145077614/"><em>Australopithecines</em></a>), to change their diet. They went from eating mainly fruits from forest trees to consuming underground bulbs and tubers found between the widely spaced trees. These were tough to extract and chew. </p>
<p>This led to the emergence through evolution of the genus <a href="https://www.maropeng.co.za/content/page/paranthropus"><em>Paranthropus</em></a> (colloquially “nutcracker man”), characterised by huge jaws and teeth. By about a million years ago they were gone. Apparently, the effort of extracting and processing these well-defended plant parts became too formidable. </p>
<h2><em>Homo habilis</em></h2>
<p>Around 2.8 million years ago, another lineage split off from the australopithecines, reversing the trend towards robust dentition. This lineage used stones chipped to serve as tools. These were used to scrape flesh from carcasses of animals killed by carnivores, and crack open long bones for their marrow content. This transition in ecology was sufficiently momentous to warrant a new generic name: <em>Homo</em>, specifically <em>habilis</em> (“handy-man”). </p>
<p>These first humans thus became scavengers on animal left-overs. They most probably exploited a time window around midday when the killers – mainly sabre-tooth cats – were resting, before hyenas arrived nocturnally to devour the leftovers. Walking upright freed their arms to carry bones away to be processed in safe sites to augment the plant-based dietary staples. </p>
<p>To facilitate such midday movements, <em>Homo habilis</em> lost its body hair; this made it possible for them <a href="https://www.nature.com/articles/nature03052">to be active</a> under conditions when fur-covered animals would soon over-heat. </p>
<h2><em>Homo erectus</em></h2>
<p>Several hundred thousand years of progressive advancements in upright walking and brain capacity led to the next major adaptive shift, exemplified by improvements in the design of stone tools. Stone cores became shaped on both sides to aid the processing of animal carcasses.</p>
<p>This led to the emergence of <a href="https://humanorigins.si.edu/evidence/human-fossils/species/homo-erectus"><em>Homo erectus</em></a> around 1.8 million years ago. These early humans had become efficient hunters. Consequently, meat and bones became reliable food resources year-round. </p>
<p>A division of labour came about. Men hunted; women gathered plant parts. This required a home base and more elaborate forms of communication about planned excursions, laying the foundations for language. </p>
<h2><em>Homo sapiens</em></h2>
<p>After 800,000 years ago, fluctuations in heat and aridity became more extreme in Africa. Finely crafted stone tools defined the transition into the Middle Stone Age, coupled with the emergence of modern <em>Homo sapiens</em> in Africa around 300 thousand years ago.</p>
<p>But despite its hunting prowess <em>Homo sapiens</em> had declined to precarious numbers in Africa by around 130,000 years ago, following an especially severe ice age. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2945812/">Genetic evidence indicates</a> that the entire human population across the continent shrank to fewer than 40,000 individuals, spread thinly from Morocco in the north to the Cape in the far south. </p>
<p>One remnant survived by inhabiting caves along the southern Cape coast, exploiting marine resources. This reliable food source fostered further advances in tool technology, and even the earliest art. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/south-africas-blombos-cave-is-home-to-the-earliest-drawing-by-a-human-103017">South Africa's Blombos cave is home to the earliest drawing by a human</a>
</strong>
</em>
</p>
<hr>
<p>The use of bows and arrows as weapons, along with spears, probably contributed crucially to the expansion of humans beyond Africa around 60,000 years ago. They spread onward through Asia and into Europe, displacing the Neanderthals. </p>
<h2>Only in Africa</h2>
<figure class="align-center ">
<img alt="A herd of large brown wildebeest is spread out across a grassy landscape, chewing the grass" src="https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505536/original/file-20230120-24-vwc5k1.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">Wildebeest grazing on the Serengeti Plains in Tanzania.</span>
<span class="attribution"><span class="source">Norman Owen-Smith</span></span>
</figcaption>
</figure>
<p>As outlined in my book, it was the abundance specifically of medium and large grazers in fertile savannas, concentrated near water in the dry season, that enabled the evolutionary transformation of a relatively puny ape into a feared hunter in Africa.</p>
<p>Africa’s high-lying interior plateau generated the seasonal dryness that restricted plant growth through its eastern and southern regions. Widespread volcanically derived soils were sufficiently fertile to foster the spread of medium-large grazers adapted to digest dry grass efficiently.</p>
<p>These especially abundant herbivores crowded around remaining waterholes, providing sufficient remnants of flesh and marrow to make scavenging a reliable means to overcome shortages of edible plant parts during the dry season. The increased dependence on meat to supplement a plant-based diet led to social coordination between male hunters and female gatherers, which in turn promoted advances in communication and tool technology supported by expanding cranial capacity. </p>
<p>If Africa had remained largely low-lying and leached of nutrients like most of South America and Australia, this would not have been possible.</p>
<p>Africa’s mobile grazers, such as wildebeest, are currently <a href="https://www.science.org/doi/10.1126/science.aay3049">being squeezed out of their sanctuaries</a> by expanding human settlements. These animals represent a global cultural heritage, having being pivotal to our evolutionary origins. We must ensure that sufficient space remains in Africa to enable their persistence despite burgeoning human populations.</p><img src="https://counter.theconversation.com/content/196398/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Norman Owen-Smith previously received funding from Sough Africa's National Research Foundation</span></em></p>Africa’s large mammal heritage has formed a deep cultural legacy for all of humankind.Norman Owen-Smith, Emeritus Research Professor of African Ecology, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1847172022-08-10T13:56:20Z2022-08-10T13:56:20ZSt. Lawrence River zones that are hostile to invasive species can be refuges for native fish<figure><img src="https://images.theconversation.com/files/476114/original/file-20220726-10610-10p0fp.jpeg?ixlib=rb-1.1.0&rect=27%2C27%2C4573%2C3421&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The round goby is an invasive fish that has become established in the St. Lawrence River over the past two decades, following its introduction into the Great Lakes.</span> <span class="attribution"><span class="source">(Cristina Charette)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Biological invasions are among the main factors contributing to the significant <a href="https://academic.oup.com/bioscience/article/48/8/607/232411">decline in biodiversity worldwide</a>. </p>
<p>Several invasive species, such as the zebra mussel (<em>Dreissena polymorpha</em>) are native to the Ponto-Caspian region, which includes the Black, Caspian and Azov Seas, and were imported to North America by transoceanic ships. These species are known to have disrupted ecosystems around the world, including those of the Great Lakes and St. Lawrence River.</p>
<p>However, the impacts of Ponto-Caspian invaders on native biodiversity, although significant, appear to have been <a href="https://link.springer.com/article/10.1007/s10530-009-9490-8">less extensive in the St. Lawrence River than in the Great Lakes</a>. This phenomenon might be explained by the river’s weaker conductivity.</p>
<p>Conductivity is the ability of water to conduct an electric current, which results from a concentration of dissolved minerals. It is highly dependent on salinity, the concentration of all salts dissolved in water.</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">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<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>Invasive species that originate from the Ponto-Caspian region have evolved in brackish waters, which are less salty than seawater, but still rich in essential minerals. When they are introduced into habitats that are low in minerals, or weaker conductivity as in the river, these species have difficulty surviving.</p>
<p>We are studying how conductivity gradients in the St. Lawrence River promote aquatic diversity in the presence of invasive species. These gradients provide native species with habitats that are unfavourable for invasive species.</p>
<h2>The round goby invades the St. Lawrence</h2>
<p>The round goby (<em>Neogobius melanostomus</em>), Ponto-Caspian invader, is an established fish that has become widespread in the St. Lawrence River <a href="https://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/212">within the past two decades following its introduction into the Great Lakes</a>. It has disrupted coastal fish communities because it <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.2011.03157.x">reproduces quickly and frequently, is highly adaptable to various habitat conditions, and behaves aggressively</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-L_24ur8Irw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The round goby is an invasive fish found in the St. Lawrence River.</span></figcaption>
</figure>
<p>The presence of the goby has been associated with the <a href="https://www.reabic.net/aquaticinvasions/2018/AI_2018_Morissette_etal.pdf">decline of several native fish species, such as the Johnny Darter</a>, and the spread of certain fish diseases, such as <a href="https://www.quebec.ca/en/agriculture-environment-and-natural-resources/animal-health/animal-diseases/viral-hemorrhagic-septicemia">viral hemorrhagic septicemia</a>. There is also evidence that the round goby contributes to the spread of <a href="https://meridian.allenpress.com/jwd/article/42/3/479/120902/TOXICITY-OF-CLOSTRIDIUM-BOTULINUM-TYPE-E">avian botulism</a> and the bioaccumulation of contaminants, such as <a href="https://bioone.org/journals/journal-of-great-lakes-research/volume-33/issue-1/0380-1330(2007)33%5b46%3aHNSILE%5d2.0.CO%3b2/How-Non-native-Species-in-Lake-Erie-Influence-Trophic-Transfer/10.3394/0380-1330(2007)33%5B46:HNSILE%5D2.0.CO;2.short">mercury, in the aquatic food chain</a>.</p>
<p>In addition, these impacts are expected to worsen with climate change, as round goby growth rates <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.2011.03157.x">will increase faster</a> with the rise of water temperatures in the Great Lakes and St. Lawrence River.</p>
<p>Most of the ecological impacts of the round goby on native fish and macroinvertebrate communities (animals without a spine and visible to the naked eye) appear to depend on its density and invasion status. <a href="https://www.sciencedirect.com/science/article/abs/pii/S0380133022000338?via%3Dihub">The impacts will be greater in areas where the species has been present in large numbers</a> and for a long time.</p>
<p>Since the spatial distribution of several invasive species (including zebra mussels) in the St. Lawrence River appears to be influenced by the water conductivity gradient, it is debatable whether this habitat characteristic represents a limiting factor in the invasion of freshwater environments by the round goby.</p>
<h2>A matter of refuge</h2>
<p>Environmental heterogeneity, namely the variation in the physical and ecological characteristics of the landscape, can play an important role in maintaining the diversity and abundance of native species in goby-invaded ecosystems. In fact, <a href="https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.1311">this diversity can generate refuges for native species in the face of biological invasion when environmental conditions</a>, such as water conductivity, restrict the abundance and impact of invaders by limiting their survival.</p>
<p>There are compelling studies — but of a limited number — on the Great Lakes that suggest that <a href="https://www.sciencedirect.com/science/article/abs/pii/S0380133009002032?via%3Dihub">wetlands (seagrass beds and marshes) are unfavourable to some key aquatic invaders</a>, notably the round goby.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457173/original/file-20220408-42947-fnto70.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">Goby harvesting in the St. Lawrence River.</span>
<span class="attribution"><span class="source">(Cristina Charette)</span></span>
</figcaption>
</figure>
<p>Our work has also shown that both habitat types, the conductivity gradient and local wetlands, limit round goby dominance. Even in places where they are present in large numbers, wetlands help mitigate their negative effects on native communities. This may be linked to the structuring effects of vegetation, which provide favourable conditions for maintaining fish and macroinvertebrate diversity.</p>
<h2>Important tools for biodiversity conservation</h2>
<p>The results of this study, while highly relevant to the risk assessment and management of round goby, were based on observations of a limited portion of the St. Lawrence River. Two major fish inventories along the St. Lawrence, the Fish Identification Nearshore Survey (FINS) and the <a href="https://catalogue.ogsl.ca/en/dataset/17b68796-fcd2-4888-8653-ecbcaadc8a91">Ichthyological Monitoring Network (RSI)</a>, conducted by the River Institute and the Québec Department of Forestry, Wildlife and Parks, respectively, now provide the opportunity to test the phenomenon on a much larger spatial scale — practically the entire freshwater portion of the St. Lawrence River.</p>
<p>Our research is one of the few freshwater studies to date that has addressed the essential but little-known role of refuges in an ecosystem with diverse environmental conditions. In addition to reducing the effects of the invasion on native biodiversity, these areas ensure their sustainability. The mitigation of the presence and quantity of the round goby in the St. Lawrence River by low-conductivity waters and the presence of wetlands present a conservation tool that can contribute to the preservation of this culturally and socio-economically important river system.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457694/original/file-20220412-10942-fm0wg8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The round goby, an invasive fish with significant impacts in the St. Lawrence River.</span>
<span class="attribution"><span class="source">(Stephany Hildebrand)</span></span>
</figcaption>
</figure>
<p>In addition, the relationship between goby abundance and water conductivity is a simple but informative tool in assessing the risk to habitats that are not yet colonized by the round goby (such as the St. Lawrence River tributaries) that may harbour fish species at risk, including the eastern sand darter (<em>Ammocrypta pelludica</em>), the channel darter (<em>Percina copelandi</em>) and the pugnose shiner (<em>Notropis anogenus</em>).</p>
<p>Our research highlights the importance of preserving a wide variety of natural habitats, including wetlands, for their beneficial effects in mitigating the negative impacts of biological invasions on freshwater biodiversity. </p>
<p>In particular, we recommend protecting the St. Lawrence River wetlands as a critical step in sustaining this ecosystem resource.</p>
<p><em>Matthew Windle of the River Institute provided data and contributed to the project. Louis Astorg developed ideas, directed and implemented the first study of our research.</em></p><img src="https://counter.theconversation.com/content/184717/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alison Derry is a member of the Interuniversity Group in Limnology (GRIL). She has received funding from the Fonds de recherche du Québec (FRQNT) - nature et technologies and from the Natural Sciences and Engineering Research Council of Canada (NSERC), Alliance project with the River Institute.</span></em></p><p class="fine-print"><em><span>Cristina Charette is a member of the Interuniversity Research Group in Limnology (GRIL). She has received funding from the Fonds de recherche du Québec - nature et technologies (FRQNT) and Mitacs.</span></em></p><p class="fine-print"><em><span>Olivier Morissette is a member of Aquatic Resources Quebec (RAQ). He has received funding from the Quebec Research Fund (FRQNT) - nature and technologies and the Natural Sciences and Engineering Research Council of Canada (NSERC).</span></em></p>Wetlands can help limit the spread of the voracious round goby, an invasive species that has infiltrated the Great Lakes and has become widespread in the St. Lawrence River.Alison Derry, Professeure agrégée, Université du Québec à Montréal (UQAM)Cristina Charette, PhD Candidate, Université du Québec à Montréal (UQAM)Olivier Morissette, Assistant professor, Université du Québec à Chicoutimi (UQAC)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1829252022-06-14T12:30:47Z2022-06-14T12:30:47ZLandsat zooms in on cities’ hottest neighborhoods to help combat the urban heat island effect<figure><img src="https://images.theconversation.com/files/467780/original/file-20220608-219-184ack.jpg?ixlib=rb-1.1.0&rect=24%2C0%2C2708%2C1755&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A street fan provides relief on a hot summer day in New York City.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/nala-pabong-holds-her-daughter-nala-fonseca-up-to-a-fan-to-news-photo/1194893">Stephen Chernin/Getty Images</a></span></figcaption></figure><p>Spend time in a city in summer and you can feel the urban heat rising from the pavement and radiating from buildings. Cities are generally hotter than surrounding rural areas, but even within cities, some residential neighborhoods get dangerously warmer than others just a few miles away.</p>
<p>Within these “<a href="https://www.sciencedirect.com/science/article/pii/0098300495000335">micro-urban heat islands</a>,” communities can experience heat wave conditions well before officials declare a heat emergency.</p>
<p>I use Earth-observing satellites and population data to map these hot spots, often on projects with NASA. Satellites like those in the <a href="https://landsat.gsfc.nasa.gov/">the Landsat program</a> have become crucial for pinpointing urban risks so cities can prepare for and respond to extreme heat, <a href="https://www.weather.gov/hazstat/">a top weather-related killer</a>. </p>
<p>Among the many things we’ve been able to track with increasingly detailed satellite data is that the hottest neighborhoods are typically low-income and often have <a href="https://doi.org/10.1029/2021EF002016">predominantly Black or Hispanic</a> residents.</p>
<h2>Two types of urban heat, both dangerous</h2>
<p>The urban heat island effect was first described in 1818, over 200 years ago, in “<a href="http://urban-climate.org/documents/LukeHoward_Climate-of-London-V1.pdf">The Climate of London</a>” by Luke Howard, an early pioneer of meteorology. </p>
<p>There are two distinct types of urban heat island: the atmospheric urban heat island and the surface urban heat island. They are measured in different ways.</p>
<figure class="align-center ">
<img alt="Two maps of the same area of Indianapolis, one showing the satellite view of pavement, buildings and greenery and the other showing the surface temperature differences, which range from 68.6 over water to 118.6" src="https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=329&fit=crop&dpr=1 600w, https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=329&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=329&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=413&fit=crop&dpr=1 754w, https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=413&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/467782/original/file-20220608-23-5os7jg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=413&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The image on the right shows the surface urban heat island of Indianapolis in July 2019. Note the higher-density built areas in red are much warmer than the cooler, more vegetated areas in blue.</span>
<span class="attribution"><span class="source">NASA/USGS Landsat</span></span>
</figcaption>
</figure>
<p>The atmospheric urban heat island, the phenomenon described by Howard, is simply the warmer air in urban areas relative to cooler air in outlying locations.</p>
<p>The surface urban heat island is the result of surfaces made up of heat-absorbing materials, such as asphalt, concrete and metal. Such materials are highly effective absorbers of heat energy from the Sun, and their surfaces warm rapidly and in turn emit the absorbed energy. You can feel the heat when you touch them. </p>
<p>The surface urban heat island directly contributes to the atmospheric urban heat island and is usually most intense on sunny days. Urbanization also contributes to the heat island effect through deforestation and the removal of other vegetation that would provide some cooling.</p>
<h2>Where communities faces the highest heat</h2>
<p>With <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">rising global temperatures</a> increasing the <a href="https://nca2018.globalchange.gov/chapter/2/">likelihood of dangerous heat waves</a>, cities need to know which neighborhoods are at high risk. Excessive heat <a href="https://www.cdc.gov/climateandhealth/pubs/extreme-heat-final_508.pdf">can lead to</a> dehydration, heat exhaustion, heat stroke and even death with prolonged exposure, and the most at-risk residents often lack financial resources to adapt.</p>
<figure class="align-center ">
<img alt="Map of Chicago showing how heat deaths clustered in the urban core during the 1995 heat wave." src="https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=541&fit=crop&dpr=1 600w, https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=541&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=541&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=680&fit=crop&dpr=1 754w, https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=680&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/467759/original/file-20220608-12-ivlytb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=680&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The July 1995 Chicago heat wave was blamed for over 739 deaths in a five-day period. Most victims were poor and elderly people who lacked air conditioning or feared opening windows because of crime. This figure shows the location of heat-related deaths clustered in areas of higher surface urban heat intensity.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1016/j.apgeog.2008.11.004">Daniel P. Johnson</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Satellite instruments can identify communities vulnerable to extreme heat because they can measure and map the surface urban heat island in high detail.</p>
<p>For example, industrial and commercial zones are frequently among the hottest areas in cities. They typically have <a href="https://doi.org/10.1371/journal.pone.0249715">fewer trees to cool the air</a> and more pavement and buildings to retain and radiate heat.</p>
<p>Certain residential layouts are also more prone to higher surface temperatures than others. These neighborhoods usually have minimal vegetation, and homes are <a href="https://www.nytimes.com/interactive/2019/08/09/climate/city-heat-islands.html">built close together, with more roads and sidewalks</a> and little green space. Often, especially in northern climates, homes in these neighborhoods were built with materials such as <a href="https://temperaturemaster.com/how-to-keep-a-brick-house-cool-in-the-summer/">brick that retain heat</a> to keep occupants warmer in the winter. Communities with many <a href="https://doi.org/10.1016/0098-3004(95)00033-5">apartment buildings and stores surrounded by parking lots</a> are also at high risk.</p>
<figure class="align-center ">
<img alt="Four kids in an inflatable pool on a sidewalk in an area of brick buildings, cement, pavement and no trees." src="https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/467777/original/file-20220608-13-dlxz8d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=489&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New York City kids in a mostly treeless neighborhood in the Bronx cool off in an inflatable pool.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/new-yorkers-cool-off-in-an-inflatable-pool-on-the-sidewalk-news-photo/81521128">Mario Tama/Getty Images</a></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two maps of New York City show how vegetation matches cooler areas by temperature." src="https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=294&fit=crop&dpr=1 600w, https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=294&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=294&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=370&fit=crop&dpr=1 754w, https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=370&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/467655/original/file-20220608-14-440sdy.png?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">Comparing maps of New York City’s vegetation and temperature shows the cooling effect of parks and neighborhoods with more trees.</span>
<span class="attribution"><a class="source" href="https://climate.nasa.gov/faq/44/can-you-explain-the-urban-heat-island-effect/">NASA/USGS Landsat</a></span>
</figcaption>
</figure>
<p>My research has found that on warm summer days, low-income communities of color can experience extreme heat conditions that are often more than 10 degrees Fahrenheit (5.5 C) warmer than surrounding areas. Other research has found <a href="https://www.nasa.gov/feature/goddard/2022/nasa-researcher-finding-ways-to-turn-down-the-heat-in-cities">similar differences</a> among neighborhoods and <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021EF002016#eft2854-bib-0007">stark racial and economic disparities</a> when it comes to heat exposure.</p>
<p>One <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021EF002016">recent study found</a> that the poorest areas were significantly hotter than the richest in 76% of urban U.S. counties. It also found that neighborhoods with large Black, Hispanic and Asian populations were in significantly hotter areas in 71% of counties, and that that difference remained even when adjusting for income. These areas tend to have less vegetation and a higher density of homes. </p>
<p>Another study looked at communities that had once been redlined, a discriminatory practice banks used in the early to mid-20th century to deny loans in racial and ethnic minority communities. Nationally, these <a href="https://www.mdpi.com/2225-1154/8/1/12">formerly redlined neighborhoods</a> were 4.6 F (2.6 C) warmer than nonredlined areas.</p>
<h2>50 years of Landsat</h2>
<p>Several <a href="https://earthdata.nasa.gov/learn/toolkits/disasters-toolkit/extreme-heat-data-toolkit">satellite systems</a> can now measure the surface urban heat island, but the Landsat program provides decades of continuous, comparable data in the detail necessary to examine variations within a city. That continuity helps scientists measure the impact of changes and track how development patterns <a href="https://doi.org/10.1016/j.scs.2021.103376">change a neighborhood’s heat profile</a>.</p>
<p>The first Landsat satellite was launched on July 23, 1972, with a sensor that collected data in green, red and near-infrared wavelengths that made it useful for mapping vegetation. Beginning with Landsat 4, launched in July 1982, scientists could map and measure thermal characteristics of Earth’s surface. Today, <a href="https://landsat.gsfc.nasa.gov/satellites/landsat-8/">Landsat 8</a> and <a href="https://landsat.gsfc.nasa.gov/satellites/landsat-9/">Landsat 9</a> are operating, and a <a href="https://landsat.gsfc.nasa.gov/satellites/landsat-next/">10th</a> is being developed.</p>
<h2>How cities can use this data to help</h2>
<p>There are numerous ways cities can use this data to help residents combat extreme heat.</p>
<p>In Indianapolis, local government and faith-based organizations have used <a href="https://www.sciencedirect.com/science/article/abs/pii/S014362281200032X">extreme heat vulnerability indices</a>, which use indicators of heat-health risk and past heat waves to highlight high-risk communities. Knowing which communities are likely to be at the highest risk allows them to guide outreach to the most vulnerable people both before and during periods of elevated temperatures.</p>
<p>New York’s “<a href="https://www1.nyc.gov/assets/orr/pdf/Cool_Neighborhoods_NYC_Report.pdf">Cool Neighborhoods NYC</a>” program includes strategically planting trees and vegetation to increase shade and evapotranspiration, which cools the surrounding area. It also discusses painting roofs and pavement light colors to reflect solar energy and educating at-risk communities about heat risk and ways they can get help.</p>
<figure class="align-center ">
<img alt="Map of Indianapolis showing how risk is pinpointed by a heat vulnerability index created by the author." src="https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=416&fit=crop&dpr=1 600w, https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=416&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=416&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=522&fit=crop&dpr=1 754w, https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=522&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/467554/original/file-20220607-24-wjln8z.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=522&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An extreme heat vulnerability index highlights areas that are more likely to experience heat-related illnesses and deaths. Darker browns indicate elevated risk. This index uses Landsat data to measure differences in surface temperature throughout the city, with socioeconomic indicators painting a highly accurate picture of community-level extreme heat health risk.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1016/j.apgeog.2012.04.006">Daniel P. Johnson</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>As the climate continues to warm and affect urban health, the Landsat satellites’ sensors are among our best tools for monitoring the thermal variations of the urban heat island. Such work also serves as one of the best examples of employing satellite-based measurements to monitor and implement response to public health threats.</p>
<p><em>This article was updated to highlight the 50th anniversary of the Landsat program.</em></p><img src="https://counter.theconversation.com/content/182925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel P. Johnson has received relevant funding from the National Aeronautics and Space Administration (NASA) and U.S. Centers for Disease Control and Prevention (U.S. CDC).</span></em></p>Extreme heat waves are putting lives in danger, with some of the hottest urban neighborhoods 10 degrees hotter or more than their wealthier neighbors. Often, these are communities of color.Daniel P. Johnson, Associate Professor of Geography, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1673672021-09-20T20:08:59Z2021-09-20T20:08:59ZClimate change is testing the resilience of native plants to fire, from ash forests to gymea lilies<figure><img src="https://images.theconversation.com/files/419732/original/file-20210907-21-zf7v0t.JPG?ixlib=rb-1.1.0&rect=138%2C24%2C3887%2C2993&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One year following the 2019/20 fires, this forest has been slow to recover.</span> <span class="attribution"><span class="source">Rachael Nolan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Green shoots emerging from black tree trunks is an iconic image in the days following bushfires, thanks to the remarkable ability of many native plants to survive even the most intense flames.</p>
<p>But in recent years, the length, frequency and intensity of Australian bushfire seasons have increased, and will worsen further <a href="https://www.ipcc.ch/assessment-report/ar6/">under climate change</a>. <a href="https://www.ipcc.ch/assessment-report/ar6/">Droughts and heatwaves are also projected to increase</a>, and climate change may also affect the <a href="https://doi.org/10.1007/s40725-018-0075-6">incidence of pest insect outbreaks</a>, although this is difficult to predict. </p>
<p>How will our ecosystems cope with this combination of threats? In our <a href="https://doi.org/10.1111/pce.14176">recently published paper</a>, we looked to answer this exact question — and the news isn’t good. </p>
<p>We found while many plants are really good at withstanding certain types of fire, the combination of drought, heatwaves and pest insects may push many fire-adapted plants to the brink in the future. The devastating Black Summer fires gave us a taste of this future. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/419743/original/file-20210907-27-18vhqlt.jpg?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"></a>
<figcaption>
<span class="caption">Examples of fire-adapted plants: prolific flowering of pink flannel flowers (upper left), new foliage resprouting on geebung (upper right), seed release from a banksia cone (lower left), and an old man banksia seedling (lower right).</span>
<span class="attribution"><span class="source">Rachael Nolan</span></span>
</figcaption>
</figure>
<h2>What happens when fires become more frequent?</h2>
<p>Ash forests are one of the most iconic in Australia, home to some of the <a href="https://theconversation.com/mountain-ash-has-a-regal-presence-the-tallest-flowering-plant-in-the-world-96021">tallest flowering plants</a> on Earth. When severe fire occurs in these forests, the mature trees are killed and the forest regenerates entirely from the seed that falls from the dead canopy. </p>
<p>These regrowing trees, however, do not produce seed reliably until they’re 15 years old. This means if fire occurs again during this period, the trees will not regenerate, and the ash forest will collapse. </p>
<p>This would have <a href="https://theconversation.com/ash-to-ashes-what-could-the-2013-fires-mean-for-the-future-of-our-forests-12346">serious consequences</a> for the carbon stored in these trees, and the habitat these forests provide for animals.</p>
<p>Southeast Australia has experienced <a href="https://www.tandfonline.com/doi/abs/10.1080/00049158.2013.848610">multiple fires since 2003</a>, which means there’s a large area of regrowing ash forests across the landscape, especially in Victoria. </p>
<p>The Black Summer bushfires burned parts of these young forests, and nearly 10,000 football fields of ash forest was at risk of collapse. Thankfully, <a href="https://www.youtube.com/watch?v=BEfCE22q8aU">approximately half of this area</a> was recovered through an artificial seeding program.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=227&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=227&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=227&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=286&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=286&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420717/original/file-20210913-15-9547bp.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=286&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ash to ashes: On the left, unburned ash forest in the Central Highlands of Victoria; on the right, ash forest which has been burned by a number of high severity bushfires in Alpine National Park. Without intervention, this area will no longer be dominated by ash and will transition to shrub or grassland.</span>
<span class="attribution"><span class="source">T Fairman</span></span>
</figcaption>
</figure>
<h2>What happens when fire seasons get longer?</h2>
<p>Longer fire seasons means there’s a greater chance species will burn at a time of year that’s outside the historical norm. This can have devastating consequences for plant populations. </p>
<p>For example, out-of-season fires, such as in winter, can <a href="https://doi.org/10.1016/j.jenvman.2019.01.083">delay maturation of the Woronora beard-heath</a> compared to summer fires, because of their seasonal requirements for releasing and germinating seeds. This means the species needs longer fire-free intervals when fires occur out of season. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/entire-hillsides-of-trees-turned-brown-this-summer-is-it-the-start-of-ecosystem-collapse-126107">Entire hillsides of trees turned brown this summer. Is it the start of ecosystem collapse?</a>
</strong>
</em>
</p>
<hr>
<p>The iconic gymea lily, a post-fire flowering species, is another plant under similar threat. <a href="https://doi.org/10.1016/j.envexpbot.2021.104634">New research</a> showed when fires occur outside summer, the gymea lily didn’t flower as much and changed its seed chemistry. </p>
<p>While this resprouting species might persist in the short term, consistent out-of-season fires could have long-term impacts by reducing its reproduction and, therefore, population size. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422061/original/file-20210920-47670-1lfpjwl.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">Out-of-season fires could have long-term impacts on gymea lilies.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>When drought and heatwaves get more severe</h2>
<p>In the lead up to the Black Summer fires, eastern Australia experienced the <a href="http://www.bom.gov.au/climate/current/annual/aus/2019/">hottest and driest year</a> on record. The drought and associated heatwaves triggered widespread canopy die-off. </p>
<p>Extremes of drought and heat can directly kill plants. And this increase in dead vegetation may <a href="https://doi.org/10.1071/WF15028">increase the intensity</a> of fires.</p>
<p>Another problem is that by coping with drought and heat stress, plants may deplete their stored energy reserves, which are vital for resprouting new leaves following fire. Depletion of energy reserves may result in a phenomenon called “<a href="https://doi.org/10.1002/ecm.1285">resprouting exhaustion syndrome</a>”, where fire-adapted plants no longer have the reserves to regenerate new leaves after fire.</p>
<p>Therefore, fire can deliver the final blow to resprouting plants already suffering from drought and heat stress.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420673/original/file-20210913-25-1wdcx7h.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">Drought stressed eucalypt forest in 2019.</span>
<span class="attribution"><span class="source">Rachael Nolan</span></span>
</figcaption>
</figure>
<p>Drought and heatwaves could also be a big problem for seeds. Many species rely on fire-triggered seed germination to survive following fire, such as many species of wattles, banksias and some eucalypts. </p>
<p>But drought and heat stress may reduce the number of seeds that get released, because they limit flowering and seed development in the lead up to bushfires, or trigger plants to release seeds prematurely. </p>
<p>For example, in Australian fire-prone ecosystems, <a href="https://doi.org/10.1002/ece3.973">temperatures between 40°C and 100°C</a> are required to break the dormancy of seeds stored in soil and trigger germination. But during heatwaves, soil temperatures can be high enough to <a href="https://doi.org/10.1002/ece3.973">break these temperature thresholds</a>. This means seeds could be released before the fire, and they won’t be available to germinate after the fire hits. </p>
<p>Heatwaves can also reduce the quality of seeds by deforming their DNA. This could reduce the success of seed germination after fire. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Burnt banksia" src="https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422059/original/file-20210920-19-rtohb4.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">Many native plants, such as banksia, rely on fire to germinate their seeds.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>What about insects? The growth of new foliage following fire or drought is <a href="https://doi.org/10.1111/j.1442-9993.1983.tb01516.x">tasty to insects</a>. If pest insect outbreaks occur after fire, they may remove all the leaves of recovering plants. This additional stress may push plants over their limit, resulting in their death. </p>
<p>This phenomenon has more typically been obverved <a href="https://doi.org/10.1111/j.1442-9993.1983.tb01516.x">in eucalypts following drought</a>, where repeated defoliation (leaf loss) by pest insects triggered dieback in recovering trees.</p>
<h2>When threats pile up</h2>
<p>We expect many vegetation communities will remain resilient in the short-term, including most <a href="https://doi.org/10.1111/1365-2745.13227">eucalpyt species</a>. </p>
<p>But even in these resilient forests, we expect to see some changes in the types of species present in certain areas and changes to the structure of vegetation (such as the size of trees). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/420657/original/file-20210913-12-1w0ymym.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">Resprouting eucalypts, one year on following the 2019-2020 bushfires.</span>
<span class="attribution"><span class="source">Rachael Nolan</span></span>
</figcaption>
</figure>
<p>As climate change progresses, many fire-prone ecosystems will be pushed beyond their historical limits. Our new research is only the beginning — how plants will respond is still highly uncertain, and more research is needed to untangle the interacting effects of fire, drought, heatwaves and pest insects. </p>
<p>We need to rapidly reduce carbon emissions before testing the limits of our ecosystems to recover from fire.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-remarkable-stories-of-flora-and-fauna-in-the-aftermath-of-australias-horror-bushfire-season-155749">5 remarkable stories of flora and fauna in the aftermath of Australia’s horror bushfire season</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/167367/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rachael Nolan receives funding from the Australian Research Council, NSW Rural Fire Service, ACT Parks and Conservation and the Hermon Slade Foundation. She is a member of the NSW Bushfire Risk Management Research Hub, which is supported by funds from the NSW Department of Planning, Industry and Environment.</span></em></p><p class="fine-print"><em><span>Andrea Leigh receives funding from the Australian Research Council. She is affiliated with The University of Technology Sydney. </span></em></p><p class="fine-print"><em><span>Mark Ooi receives funding from the ARC. and the Commonwealth Department of Agriculture, Water and the Environment. He is a member of the NSW Bushfire Risk Management Research Hub, which is supported by funds from the NSW Department of Planning, Industry and Environment.</span></em></p><p class="fine-print"><em><span>Ross Bradstock receives funding from the NSW Rural Fire Service and the NSW Department of Planning, Industry and Environment via the NSW Bushfire Risk Management Research Hub, the Bushfire and Natural Hazards CRC and the ARC.</span></em></p><p class="fine-print"><em><span>Tim Curran receives funding from the New Zealand Ministry for Business, Innovation and Employment (MBIE), Fire and Emergency New Zealand, the Miss E L Hellaby Indigenous Grasslands Research Trust, Marlborough District Council, and the Lincoln University Argyle Fund. Tim is the President of the New Zealand Ecological Society.</span></em></p><p class="fine-print"><em><span>Tom Fairman has received funding from Australian Research Council and has previously worked in forest management and research for the Victorian Government.</span></em></p><p class="fine-print"><em><span>Víctor Resco de Dios receives funding from MICINN and Velux Fundation. </span></em></p>Many plants are really good at withstanding bushfires, but the combination of drought, heatwaves and pest insects under climate change may push them to the brink.Rachael Helene Nolan, Postdoctoral research fellow, Western Sydney UniversityAndrea Leigh, Associate Professor, Faculty of Science, University of Technology SydneyMark Ooi, Senior Research Fellow, UNSW SydneyRoss Bradstock, Emeritus professor, University of WollongongTim Curran, Associate Professor of Ecology, Lincoln University, New ZealandTom Fairman, Future Fire Risk Analyst, The University of MelbourneVíctor Resco de Dios, Profesor de Incendios y Cambio Global en PVCF-Agrotecnio, Universitat de LleidaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1662162021-08-18T15:09:41Z2021-08-18T15:09:41ZRepairing ozone layer is also reducing CO₂ in the atmosphere – new study<figure><img src="https://images.theconversation.com/files/416734/original/file-20210818-23-19uzpwb.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5098%2C3548&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/view-earth-space-blue-planet-deep-296927024">Studio23/Shutterstock</a></span></figcaption></figure><p>Spring 2060. In dark glasses, a wide sunhat and with what little exposed skin left caked in sun cream, a child stares at the woodland across from their house. It looks scraggly and stunted, and with far fewer leaves than in the old photos she has seen. Still, no time to dwell on it: there’s a <a href="https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/sun-uv-and-cancer/the-uv-index-and-sunburn-risk">UV index</a> of 20 and she’s already spent five minutes outside.</p>
<p>Thankfully, this is not our future. Due to steps the world took in the 1980s to protect the <a href="https://ozone.unep.org/20-questions-and-answers">ozone layer</a>, a region of the upper atmosphere that absorbs the Sun’s harmful ultraviolet (UV) radiation, we have one less environmental problem to worry about.</p>
<p>In the mid-1970s, scientists realised that the ozone layer was being depleted by the growing use of <a href="https://gml.noaa.gov/hats/publictn/elkins/cfcs.html">chlorofluorocarbons</a> (CFCs) as refrigerants and as propellants in aerosol cans, among other applications. With the 1987 signing of the <a href="https://theconversation.com/uk/topics/montreal-protocol-3788">Montreal Protocol</a>, which was later strengthened by numerous amendments and ratified by 197 countries, the world phased out CFCs. Today, CFC levels in the atmosphere are <a href="https://agage.mit.edu/data/agage-data">falling</a> and the ozone layer is <a href="https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/#topics-5">beginning to recover</a>. </p>
<figure class="align-center ">
<img alt="A bin full of discarded aerosol cans." src="https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.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">CFCs are nontoxic and nonflammable, making them useful in everything from hair care to household cleaning.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/circa-1990-bucket-full-empty-aerosol-106925534">Joseph Sohm/Shutterstock</a></span>
</figcaption>
</figure>
<p>But what if the Montreal Protocol was never signed? What would the world we managed to avoid have looked like? This is the subject of <a href="https://www.nature.com/articles/s41586-021-03737-3">a new study</a> led by me with an international team of collaborators.</p>
<p>In earlier research, scientists showed there would have been thousands more <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2012.01223.x/full">skin cancer cases</a> in such a world, where the ozone layer is thinner and higher levels of UV radiation reach the planet’s surface. There would also have been <a href="https://www.pnas.org/content/104/12/4814">additional climate warming</a>, since CFCs, like carbon dioxide (CO₂), are also greenhouse gases, although far more potent. Our focus was on what could have happened to vegetation.</p>
<p>Like humans, plants are damaged when <a href="https://www.sciencedirect.com/science/article/abs/pii/000527289090156X">exposed to high UV levels</a>. Plants absorb CO₂ as they grow, but when UV radiation increases by 10%, <a href="https://pubs.rsc.org/en/content/articlelanding/2011/pp/c0pp90035d/">plants accrue 3% less biomass</a>. Without the Montreal Protocol, we estimated that UV levels would have been 4.5 times higher on average globally than today at the end of the century. We also estimated that by 2050, European, Asian and North American UV levels would be higher than they are in the present-day tropics. </p>
<p>Overall, this means that more of the CO₂ humans emit would have remained in the atmosphere, rather than being locked up in plants and the soil. And this extra CO₂ would have led to more global warming.</p>
<h2>A world without the Montreal Protocol</h2>
<p>Using computer models to represent the climate, the atmosphere’s chemistry, vegetation and the carbon cycle, we simulated two worlds. The first assumed that <a href="https://www.nature.com/articles/249810a0">the 1974 paper</a> alerting the world to the dangers of CFCs was never published and their use grows at <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.0610328104">3% a year</a>. The second is a world where CFCs are controlled and the ozone layer recovers, the world we live in now and are on track to inhabit. </p>
<p>Apart from the CFCs, the two simulated worlds are identical. In both, CO₂ and other greenhouse gas emissions follow an <a href="https://ar5-syr.ipcc.ch/topic_futurechanges.php#box_2_2">intermediate scenario</a> for the 21st century, which is one of several used to inform the UN’s <a href="https://theconversation.com/ipcc-report-how-to-make-global-emissions-peak-and-fall-and-whats-stopping-us-165830">Intergovernmental Panel on Climate Change reports</a>. </p>
<p>The world in which CFCs were phased out looks like what we would expect from <a href="https://theconversation.com/this-is-the-most-sobering-report-card-yet-on-climate-change-and-earths-future-heres-what-you-need-to-know-165395">warmer future climates</a>. Global temperatures increase, with all their <a href="https://theconversation.com/3-dangers-of-rising-temperatures-that-could-affect-your-health-now-105028">negative consequences</a>, but – as we expect for the real world – the ozone layer recovers to its historic levels by the middle of the century. In the other world, the <a href="https://www.earthobservatory.nasa.gov/features/WorldWithoutOzone">ozone layer drastically thins</a> and by the end of the century ozone concentrations everywhere fall below levels seen in the <a href="https://earthobservatory.nasa.gov/world-of-change/Ozone">Antarctic ozone hole</a>.</p>
<figure class="align-center ">
<img alt="A satellite image of the southern hemisphere depicting relative ozone levels in the atmosphere." src="https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.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">The Antarctic ozone hole recorded at its greatest extent in September 2006.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Montreal_Protocol#/media/File:NASA_and_NOAA_Announce_Ozone_Hole_is_a_Double_Record_Breaker.png">NASA</a></span>
</figcaption>
</figure>
<p>By the 2050s, because of UV damage, plants in the world where CFC use continues unabated absorb half the carbon they do in the world where CFCs were phased out. By the end of the century, plants in this high-CFC world absorb less than 15% of the carbon they do in the other world, resulting in 30% less carbon stored in plants and soils. This means 30% more CO₂ in the atmosphere by the end of the century, which adds 0.8°C more warming to the climate.</p>
<p>By itself, this 0.8°C would be enough to take current global temperatures (just over 1°C above the <a href="https://climate.nasa.gov/vital-signs/global-temperature/">pre-industrial average</a>) to beyond the 1.5°C level that represents the most ambitious target of the <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">Paris Agreement</a>. Adding the 1.7°C that would have resulted from the greenhouse effect of CFCs themselves means that an extra 2.5°C of warming was prevented by the Montreal Protocol.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four different world maps depicting declines in carbon uptake by plants across the 21st century." src="https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Plants would take up much less carbon worldwide by the late 21st century if CFC use continued unabated.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41586-021-03737-3">Young et al. (2021)/Nature</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While we have avoided the world from our simulations, threats to the ozone layer still exist. Some scientists favour counteracting climate change by emulating the global cooling effects of <a href="https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate">large volcanic eruptions</a> – injecting particles into the upper atmosphere in a process known as <a href="https://theconversation.com/should-we-engineer-the-climate-a-social-scientist-and-natural-scientist-discuss-104516">stratospheric sulphate geoengineering</a>. </p>
<p>But this could <a href="https://science.sciencemag.org/content/320/5880/1201.abstract">deplete the ozone layer</a>. Our study shows that the knock-on effect on the biosphere must be considered in any impact assessment of such actions. </p>
<p>For its effectiveness in acting on dire scientific warnings, it’s tempting to think of the Montreal Protocol as a model for <a href="https://ukcop26.org/">climate negotiations</a>. Yet with just a handful of companies making CFCs and alternative chemicals readily available, the ozone issue was far more straightforward than reducing emissions from fossil fuels.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/shrinking-hole-in-the-ozone-layer-shows-what-collective-action-can-achieve-62007">Shrinking hole in the ozone layer shows what collective action can achieve</a>
</strong>
</em>
</p>
<hr>
<p>Nevertheless, as well as protecting the ozone layer, the Montreal Protocol has itself been a phenomenally successful climate treaty. It has controlled not only the emissions of highly potent greenhouse gases like CFCs, but, as we have shown, it has avoided additional CO₂ levels through protecting the world’s plant life.</p><img src="https://counter.theconversation.com/content/166216/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Young receives funding from the Engineering and Physical Sciences Research Council. </span></em></p>New research shows how the Montreal Protocol protected vegetation, helping keep carbon out of the atmosphere.Paul Young, Senior Lecturer in Atmospheric and Climate Science, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1581002021-04-16T14:43:52Z2021-04-16T14:43:52ZUK land now stores 7% more carbon than 300 years ago – what that means for the environment<figure><img src="https://images.theconversation.com/files/395460/original/file-20210416-23-qpwjh5.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6720%2C4466&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/golden-sunset-sunrise-light-on-lone-1938816559">Stephen Bridger/Shutterstock</a></span></figcaption></figure><p>Limiting global warming to 1.5°C and avoiding the worst effects of climate change will take more than eliminating greenhouse gas emissions. The world will also need to capture and store a lot of carbon dioxide (CO₂) from the atmosphere. </p>
<p>Land offers one natural way of doing this. The soil and everything that grows in it, including all plants and trees, represents <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter06_FINAL.pdf">about half of all</a> organic carbon globally. This is the carbon that’s bound up in living and decaying matter, as opposed to rocks and minerals. Depending on how humans treat it, the land can act as a net sink or source of carbon, either slowing or accelerating climate change. Planting trees can lock carbon away while deforestation and tilling the soil in agriculture can release it. </p>
<p>Since the dawn of the Industrial Revolution, the UK has emitted about <a href="https://ourworldindata.org/co2/country/united-kingdom?country=%7EGBR">77 billion tonnes of CO₂</a>. But how much has the country’s land area absorbed over the same period? <a href="https://www.sciencedirect.com/science/article/pii/S2213305421000126#bib0030">Our new study</a> set out to find an estimate by modelling natural cycles of carbon, nitrogen and phosphorus. </p>
<p>We found that over the last 300 years, the UK’s land carbon store has grown by about 7%, with vegetation storing 13% more carbon and soil 5% more than it did in the 18th century. Carbon storage increased most in forests and heathlands, and fell by the greatest amount in areas which were converted to arable farmland. </p>
<p>So the UK’s land carbon sink is working harder today than it was three centuries ago. Is that a good thing? As it turns out, not really. </p>
<h2>Right direction, wrong reason</h2>
<p>Since 1700, land carbon storage in the UK has increased by 233 million tonnes. That’s equivalent to 855 million tonnes of CO₂. The UK is one of the world’s largest historical emitters of carbon, so this only equates to 1.1% of the nation’s estimated emissions over the same period. But there’s a bigger problem: land-based carbon stores in the UK are unlikely to continue growing in the future for several reasons. </p>
<p>The biggest driver of the increase was pollution. When fertilisers are used in agriculture or fossil fuels are burned, these processes release reactive forms of nitrogen into the atmosphere. This is deposited on the land when it rains. </p>
<p>Since the availability of nitrogen normally limits how much plants can grow, this additional nitrogen <a href="https://theconversation.com/carbon-catch-22-the-pollution-in-our-soil-78718">acts like extra fertiliser</a>, boosting the amount of carbon that vegetation can capture. More leaf and plant litter is produced, which rots and delivers carbon to the soil.</p>
<p>But areas which were converted to farmland showed steep declines in the size of their carbon stores. When land is cleared of vegetation, the carbon stored in it is lost. Even though farmers add more nitrogen to arable land through fertilisers, the crop plants that grow are harvested, and so their carbon doesn’t end up stored in the soil.</p>
<p>The net increase in the carbon that the UK’s land is storing came from the gains across natural habitats fertilised by nitrogen. These were only slightly larger than the carbon losses from land converted for agriculture. And plants won’t continue to respond to all the extra nitrogen from atmospheric pollution forever. Other factors, such as sunlight, or the availability of phosphorus and other important nutrients, will come into play and limit growth, restricting how much more carbon can be stored in vegetation. </p>
<p>To keep the land soaking up carbon this way, we’d need to continue releasing nitrogen into the atmosphere by burning fossil fuels and applying fertilisers to crops at the current rate. This isn’t a good solution. All that nitrogen seeps into waterways where it can deplete oxygen and kill aquatic wildlife. It also contributes to <a href="https://doi.org/10.1016/j.envpol.2021.117017">plant biodiversity loss</a>, as few plant species are adapted to cope with the extra nitrogen, which also increases the acidity of the soil.</p>
<p>Soil on arable farmland is still losing carbon, while gains in natural habitats are slowing. If these trends continue, the small net gain in carbon storage that we’ve observed across the UK since the 18th century could be reversed.</p>
<figure class="align-center ">
<img alt="Gnarled oak trees grow out of mossy boulders." src="https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395459/original/file-20210416-19-oz8sj1.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">A recent report suggested that just 7% of the UK’s woodlands are in a good condition.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/ancient-gnarled-stunted-oak-tree-trunks-213662014">Helen Hotson/Shutterstock</a></span>
</figcaption>
</figure>
<p>Continuing to pollute just to maintain this thin advantage is not an option. But the news isn’t all bad. Changing the way people manage the land by reducing or preventing soil tillage, switching crops grown regularly and adding ones which can fix nitrogen like legumes and using manure-based fertilisers that add organic matter can <a href="https://www.4p1000.org/">sequester carbon in agricultural soils</a>.</p>
<p>Housing, food and energy production: the demands on the world’s land are high, but they’re particularly acute in a small country like the UK. Practices like <a href="https://theconversation.com/britain-needs-to-grow-more-trees-are-sheep-farms-the-answer-145872">rewilding</a> – where land ecosystems are allowed to naturally regenerate – can help permanently shift more carbon into the land without polluting the environment. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-crisis-the-countryside-could-be-our-greatest-ally-if-we-can-reform-farming-126304">Climate crisis: the countryside could be our greatest ally – if we can reform farming</a>
</strong>
</em>
</p>
<hr>
<p>The country has a long way to go to meet its 2050 net zero emissions target, but taking better care of the UK’s soil is a critical first step.</p><img src="https://counter.theconversation.com/content/158100/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jess Davies receives funding from UKRI, Defra and the EU Commission. </span></em></p><p class="fine-print"><em><span>Victoria Janes-Bassett 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>Scientists need to know how much we can rely on the land to offset our emissions.Victoria Janes-Bassett, Senior Research Associate in Sustainable Land Management, Lancaster UniversityJess Davies, Chair Professor in Sustainability, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1575902021-03-30T18:55:52Z2021-03-30T18:55:52ZEven after the rains, Australia’s environment scores a 3 out of 10. These regions are struggling the most<figure><img src="https://images.theconversation.com/files/392089/original/file-20210328-19-uwnc5s.jpg?ixlib=rb-1.1.0&rect=0%2C16%2C5381%2C3587&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Improved weather conditions have pulled Australia’s environment out of its worst state on record, but recovery remains partial and precarious, <a href="http://www.ausenv.online/">new research</a> reveals.</p>
<p>Each year, we collate a vast number of measurements on the state of our environment. The data are collected in many different ways – including satellites, field stations and surveys – then combined to produce an overall national score.</p>
<p>A year ago, after prolonged drought and devastating bushfires, Australia’s environment scored a shocking 0.8 out of ten. Our new research shows nature started its long road to recovery in 2020, especially in New South Wales and Victoria. Some of the regions with the poorest scores have high levels of social disadvantage, which risks being further entrenched by environmental disasters such as drought, bushfire and heatwaves.</p>
<p>Nationally, Australia’s environmental condition score increased by 2.6 points last year, to reach a (still very low) score of 3.2. But overall conditions across large swathes of the country remain poor. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=476&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=476&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=476&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=598&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=598&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390898/original/file-20210322-19-1w6hdbn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=598&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Environmental Condition Score for 2020 by state and territory.</span>
<span class="attribution"><span class="source">ANU Fenner School</span></span>
</figcaption>
</figure>
<h2>Scores rising but still in the red</h2>
<p>From a long list of environmental indicators we report on, seven are selected to calculate an overall score for each region, as well as nationally.</p>
<p>These indicators – high temperatures, river flows, wetlands, soil health, vegetation condition, growth conditions and tree cover – are chosen because they allow a comparison against previous years. See the graphic below to find the score for your region.</p>
<p>The largest improvements occurred in NSW and Victoria thanks to good rains. The poorest conditions occurred in the Northern Territory and Western Australia, where there was little solace from dry conditions.</p>
<p>Comparing local government areas, the best conditions occurred in Nillubik Shire on the northern edge of Melbourne. In contrast, the worst conditions occurred in Katherine in the Northern Territory and in the Shire of Ngaanyatjarraku in remote WA.</p>
<hr>
<p><iframe id="tc-infographic-578" class="tc-infographic" height="850px" src="https://cdn.theconversation.com/infographics/578/d7af93fc2a78ca90970ef1fd79fec45649e6bc66/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<hr>
<style>
@media only screen and (max-width: 450px) {
iframe.box {display:none}
}
@media only screen and (min-width: 451px) and (max-width: 1460px) {
iframe.box {display:block}
}
</style>
<iframe class="box" src="https://flo.uri.sh/visualisation/5712794/embed" title="Interactive or visual content" frameborder="0" scrolling="no" style="width:100%;height:650px;" sandbox="allow-same-origin allow-forms allow-scripts allow-downloads allow-popups allow-popups-to-escape-sandbox allow-top-navigation-by-user-activation" width="100%" height="400"></iframe>
<h2>From drought to rain</h2>
<p>2020 started as badly as 2019 ended – with extreme temperatures, drought and fires, especially in Australia’s southeast. The Sydney suburb of Penrith was the hottest place on Earth on January 4 and, following the bushfires, Canberra had the most dangerous air quality in the world for several days. Clearly, climate change is already affecting our cities and nature.</p>
<p>By the end of summer, the high temperatures also caused another mass coral bleaching in the Great Barrier Reef – the third such event in five years. </p>
<p>Only in February-March did the weather turn, providing good and in some areas very plentiful rains – for example along the NSW coast. Later in the year officials declared an La Niña event – an ocean circulation pattern that normally encourages rainfall in Australia. </p>
<p>While rainfall was not extraordinarily high, it lifted most regions in eastern Australia out of extreme drought. Some parts of northern and western Australia missed out, however, and in some areas the drought deepened.</p>
<p>Taken as an average over the year and over the country, rainfall was 10% above the average for the previous two decades. The number of hot days – those reaching 35°C – was 11% or nine days more than the 20-year average.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=456&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=456&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390899/original/file-20210322-13-pfnj75.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=456&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Values for 15 environmental indicators in 2020, expressed as the change from average 2000-2019 conditions. Similar to national economic indicators, they provide a summary but also hide regional variations, complex interactions and long-term context.</span>
<span class="attribution"><span class="source">ANU Fenner School</span></span>
</figcaption>
</figure>
<p>The improved rainfall helped replenish dried soils, and national average soil moisture was close to average. Growth conditions for the NSW wheatbelt were the best in many years and tree cover increased in northern and eastern Australia. </p>
<p>The rain refilled many dams and reservoirs, especially in Canberra and Sydney. It also made some eastern rivers flow again, including the Darling River in NSW. But with such dry starting conditions, wetlands in inland eastern Australia filled only modestly and <a href="https://newsroom.unsw.edu.au/news/science-tech/waterbird-numbers-and-wetland-areas-declining-despite-temporary-relief-aerial">waterbird numbers</a> remained low.</p>
<p>Drought persisted across large swathes of inland northern and western Australia, where in some parts, vegetation growth conditions were the worst in decades. And the surplus rain was often not enough to reach wetlands, which continued to shrink. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wake-up-mr-morrison-australias-slack-climate-effort-leaves-our-children-10-times-more-work-to-do-157136">Wake up, Mr Morrison: Australia's slack climate effort leaves our children 10 times more work to do</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="New shoots in forest after fire" src="https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392093/original/file-20210328-13-1aykm1l.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">Signs of life: some parts of Australia have benefited from recent rain.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Bushfires: few but locally severe</h2>
<p>Fire activity in vast areas of inland Australia was very low, because a run of dry years did not leave much dry grass to burn. </p>
<p>Nationally, the total area burnt was 17 million hectares – 90% below the 20-year average. This led to 80 million tonnes of carbon emissions (43% below average).</p>
<p>Fire activity was not low everywhere. In southeast Australia, fires in <a href="http://wenfo.org/ausenv/#/2020/Burned_area/Grid/Actual/Local_Government%20Areas/bar,options/-37.49/147.33/7/none/Roadmap/Opaque">southern NSW, East Gippsland and the ACT</a> severely damaged forests and other ecosystems as well as people and property.</p>
<p>The full ecological damage of the Black Summer fires was not entirely apparent in 2020. That’s partly because COVID-19 restrictions made the situation difficult to assess.</p>
<p>The fires burned <a href="https://theconversation.com/six-million-hectares-of-threatened-species-habitat-up-in-smoke-129438">more than 80% of the habitat of 30 threatened species</a>, and may have been the death blow for several. Food shortages and <a href="https://theconversation.com/fire-ravaged-kangaroo-island-is-teeming-with-feral-cats-its-bad-news-for-this-little-marsupial-141201">feral cats</a> further reduced populations of surviving animals in the burnt ecosystems. </p>
<p>But some wildlife proved unexpectedly resilient. For example, a great effort by citizen scientists showed <a href="https://theconversation.com/australians-recorded-frog-calls-on-their-smartphones-after-the-bushfires-and-the-results-are-remarkable-146578">frogs rebounded well</a> after the rains. </p>
<p>Another 15 species were added to the Threatened Species List in 2020. In good news, three species were removed from the list, including two species of tree frogs that recovered from the global <a href="https://theconversation.com/deadly-frog-fungus-has-wiped-out-90-species-and-threatens-hundreds-more-113846">chytrid fungus</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-remarkable-stories-of-flora-and-fauna-in-the-aftermath-of-australias-horror-bushfire-season-155749">5 remarkable stories of flora and fauna in the aftermath of Australia’s horror bushfire season</a>
</strong>
</em>
</p>
<hr>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/xJme6rIBYys?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Stopping the slow train wreck</h2>
<p>The accelerating impacts of climate change will not stop here. New records will inevitably be broken. Heat, drought and fire will again damage our environment and lives. <a href="https://theconversation.com/existential-threat-to-our-survival-see-the-19-australian-ecosystems-already-collapsing-154077">Some ecosystems will be lost forever</a>. But even worse outcomes can be avoided – <em>if</em> the world can rein in greenhouse gas pollution. </p>
<p>There’s cause for cautious optimism. <a href="https://theconversation.com/bidens-senate-majority-doesnt-just-super-charge-us-climate-action-it-blazes-a-trail-for-australia-153090">International pressure</a> may force the Morrison government’s hand on climate action. <a href="https://theconversation.com/nsw-has-joined-china-south-korea-and-japan-as-climate-leaders-now-its-time-for-the-rest-of-australia-to-follow-149731">Several states</a> and territories have already taken decisive climate action. Low-emission energy and transport are advancing quickly. As individuals we can fly and drive less, get solar panels and divest from fossil fuel companies. </p>
<p>In the meantime, we must adapt to inevitable climate change and reduce other pressures on our ecosystems. Citizen scientists have proven essential in monitoring how individual species are faring – so download that app and enjoy nature even more. And plant a few <a href="https://theconversation.com/every-year-in-australia-nature-grows-8-new-trees-for-you-but-that-alone-wont-fix-climate-change-146922">trees</a> to help nature along.</p>
<p>Finally, pressure your local, state and national politicians. Ask them: how are you addressing vegetation loss, invasive pests and over-extraction from rivers? If you don’t like the answer, tell them, or try to vote them out.</p>
<p>With greater urgency and some luck, there is still much to be salvaged. </p>
<p>The full report and a video summary <a href="http://www.ausenv.online/">are available here</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/our-turtle-program-shows-citizen-science-isnt-just-great-for-data-it-makes-science-feel-personal-155142">Our turtle program shows citizen science isn't just great for data, it makes science feel personal</a>
</strong>
</em>
</p>
<hr>
<p><em>This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. It is supported by a philanthropic grant from the Paul Ramsay foundation. You can read the rest of the stories <a href="https://theconversation.com/au/topics/disaster-and-resilience-series-97537">here</a>.</em></p><img src="https://counter.theconversation.com/content/157590/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Australia’s Environment is produced by the ANU Fenner School for Environment & Society with support from TERN, an NCRIS-enabled National Research Infrastructure. Albert Van Dijk receives or has previously received funding from several government-funded agencies, grant schemes and programmes.</span></em></p><p class="fine-print"><em><span>Marta Yebra and Shoshana Rapley do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research shows nature started its long road to recovery in 2020 – especially in NSW and Victoria. But overall conditions across large swathes of the country remain poor.Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National UniversityMarta Yebra, Associate Professor in Environment and Engineering, Australian National UniversityShoshana Rapley, Research assistant, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1308762020-03-31T03:34:12Z2020-03-31T03:34:12ZIf you’re worried about bushfires but want to keep your leafy garden, follow these tips<figure><img src="https://images.theconversation.com/files/316116/original/file-20200219-10995-3lm921.jpg?ixlib=rb-1.1.0&rect=315%2C880%2C4088%2C2790&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock/autau</span></span></figcaption></figure><p>As we witnessed last summer, the number of houses destroyed during bushfires in Australia has not been stemmed by advances in weather forecasting, building design and the increased use of large water-bombing aircraft. </p>
<p><a href="https://www.abc.net.au/news/2020-02-19/australia-bushfires-how-heat-and-drought-created-a-tinderbox/11976134">At the latest count,</a> more than 3,500 homes were destroyed the summer just gone, which makes this the most destructive bushfire season in Australia’s history.</p>
<p>The principal reason for the continually high rate of destruction is that <a href="https://journals.ametsoc.org/doi/full/10.1175/2010WCAS1063.1" title="Influence of Location, Population, and Climate on Building Damage and Fatalities due to Australian Bushfire: 1925–2009">so many homes are being built close to bushland</a>. <a href="https://theconversation.com/a-history-of-vulnerability-putting-tasmanias-bushfires-in-perspective-11530">An estimated</a> 85% of all houses destroyed in bushfires in Australia are within 100m of the bush.</p>
<p>It follows that clearing vegetation around houses is at the <a href="https://www.cfa.vic.gov.au/plan-prepare/clearing-trees-and-vegetation">forefront of advice</a> <a href="https://www.qld.gov.au/environment/land/management/vegetation/disasters/fire/exempt">provided by fire authorities to homeowners</a> in bushfire-prone areas.</p>
<p>A home without trees and shrubs around it is the safest option during a bushfire. But realistically, many people will want to retain some vegetation. And there are ways to do this sensibly.</p>
<p><iframe id="z1G0C" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/z1G0C/3/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Is clearing bushland the solution?</h2>
<p><a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0029212" title="Land Management Practices Associated with House Loss in Wildfires">Research shows</a> houses close to bushland are more effectively protected by clearing trees and shrubs within approximately 40m of the home.</p>
<p>There are laws in most states and territories, such as New South Wales’ <a href="https://www.rfs.nsw.gov.au/news-and-media/media-releases/1050-vegetation-clearing-entitlement-code-of-practice-amendments">10/50</a> Vegetation Clearing Scheme, that permit this to some extent.</p>
<p>But if all homeowners in bushfire-prone areas exercised their right to clear trees and shrubs, places such as the Blue Mountains, Perth Hills, Mount Lofty Ranges, Dandenongs and our coastal towns like Mallacoota, Margaret River and Batemans Bay would be vastly different in character.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-a-bushfire-can-destroy-a-home-110795">How a bushfire can destroy a home</a>
</strong>
</em>
</p>
<hr>
<p>Residents and tourists are attracted to these areas for the aesthetics, privacy, wildlife and shade native trees and shrubs provide.</p>
<p>A <a href="https://academic.oup.com/ajae/article-abstract/97/1/299/135463" title="Capitalized Amenity Value of Native Vegetation in a Multifunctional Rural Landscape">study of rural-residential areas north of Melbourne</a> found property values were higher where there was a considerable cover of native vegetation. We not only like our native bush, we are prepared to pay for it.</p>
<p>Because many people value trees and shrubs around their homes, it is not realistic to expect uniformly low fuel loads within bushfire-prone parts of Australia.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/aflYso_0X68?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Can we have our cake and eat it?</h2>
<p>We analysed data collected before and after the 2009 Black Saturday Fires, in which 2,133 houses were destroyed.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0169204618300598" title="Options for reducing house-losses during wildfires without clearing trees and shrubs">We found that</a> the extent of “greenness” of vegetation surrounding homes had a bearing on whether the structure withstood fire.</p>
<p><a href="http://www.bom.gov.au/climate/austmaps/about-ndvi-maps.shtml">Greenness refers to</a> the extent to which plants are actively growing. Houses with trees and shrubs within 40m were slightly less likely to be destroyed if the vegetation had relatively high values of “greenness”, as compared to houses surrounded by vegetation with low greenness value. </p>
<p>This makes sense because greener vegetation, typically with higher moisture content, has lower flammability, requires more energy to ignite and therefore can reduce the intensity of a fire.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australian-building-codes-dont-expect-houses-to-be-fire-proof-and-thats-by-design-129540">Australian building codes don't expect houses to be fire-proof – and that's by design</a>
</strong>
</em>
</p>
<hr>
<p>Thus, watering your garden through summer, if this is feasible, or choosing plants with high moisture content (such as <a href="https://www.yates.com.au/plants/succulents">succulents</a>) may reduce the bushfire risk compared with the same amount of vegetation with a lower moisture content.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0169204618300598" title="Options for reducing house-losses during wildfires without clearing trees and shrubs">We also found</a> the risk to houses during bushfire was slightly less where trees and shrubs within 40m were not continuous, but instead arranged as discrete patches separated by a ground layer with low fuel hazard, such as mown grass.</p>
<p>As trees and shrubs become less continuous the heat transfer between patches becomes less efficient and the intensity of the fire is likely to decline.</p>
<p>Provided bushfires in your area come from a predictable direction, retaining more trees and shrubs downwind of this direction from your house <a href="https://www.sciencedirect.com/science/article/pii/S0169204618300598" title="Options for reducing house-losses during wildfires without clearing trees and shrubs">poses less risk</a> than the same cover of trees and shrubs retained upwind from your house.</p>
<p>This makes sense because <a href="https://theconversation.com/how-a-bushfire-can-destroy-a-home-110795">burning embers</a>, which are the main cause of house losses during bushfires, travel in the direction of the wind.</p>
<h2>You can’t eliminate risk from bushfires</h2>
<p>We must emphasise that while these strategies can strike a balance between retaining trees and shrubs and preparing for bushfires, they will not guarantee your home will survive a bushfire – especially <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0029212">in severe fire weather</a>.</p>
<p>So in addition to vegetation management, other strategies – such as building design, adequate insurance and evacuating early to a safer place – should be considered in every household’s bushfire planning.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/12-simple-ways-you-can-reduce-bushfire-risk-to-older-homes-122712">12 simple ways you can reduce bushfire risk to older homes</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/130876/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip Gibbons has received funding from the Australian Research Council and various Australian federal and state government agencies.</span></em></p><p class="fine-print"><em><span>Dr Geoff Cary receives funding from the Australian Research Council, the Australian Centre for International Agricultural Research (ACIAR), and the Bushfire and Natural Hazards CRC, and somewhat recently received funding from the National Health and Medical Research Council, Australian Greenhouse Office/Department of Climate Change Greenhouse Action in Regional Australia funding schemes, NSW Department of Environment & Conservation, and US National Science Foundation.</span></em></p>With a bit of sensible planning, you can retain plants close to your home without creating a huge bushfire risk.Philip Gibbons, Professor, Australian National UniversityGeoff Cary, Associate Professor, Bushfire Science, Fenner School of Environment and Society, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1250692019-10-11T09:38:32Z2019-10-11T09:38:32ZWhat science tells us about fire hazards facing Cape Town and its surrounds<figure><img src="https://images.theconversation.com/files/296410/original/file-20191010-188819-xmrl54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A fire rages through wetlands close to Cape Town in February 2017.</span> <span class="attribution"><span class="source">EPA/Nic Bothma</span></span></figcaption></figure><p>South Africa’s Cape Peninsula – home to the picturesque city of Cape Town – is part of the only region in the world with fynbos. Fynbos is the world’s <a href="https://thefynbosguy.com/fynbos-easy-introduction/">most diverse vegetation type</a> – even more so than tropical rainforests. </p>
<p>Cape Town city surrounds the Cape Peninsula, the south-western extremity of the African continent, the remaining natural areas forming part of Table Mountain National Park. </p>
<p>The city has encroached ever closer to nature, developing deeper into the mountain fynbos. Alien plantations have resulted in <a href="https://theconversation.com/invasive-alien-plants-in-south-africa-pose-huge-risks-but-they-can-be-stopped-94186">infestations of alien trees</a>. Some citizens have been careless with inappropriate construction on the urban edge by building too high up on the mountains. </p>
<p>On top of this, various factors have resulted in a failure to maintain the desired fire regime, particularly of fires at 12-15 year intervals. As a result there has been a dangerous build-up of vegetation – fuel loads – in some places. </p>
<p>The Western Cape is entering the summer season – its driest, given that rains fall in the winter. <a href="https://www.iol.co.za/capeargus/news/cape-faces-fire-catastrophe-as-experts-fear-citys-worst-fire-season-lies-ahead-33176036">Fears have been mounting</a> that this year’s fire season might be the worst on record. </p>
<p>As a group of climate scientists and fynbos ecologists, we provide some context and background to the threat, based on available scientific research. We also point to what steps can be taken to help mitigate runaway fires in the region.</p>
<h2>Fynbos and fire</h2>
<p>Fynbos is both <a href="https://www.researchgate.net/publication/248531724_Managing_fires_on_the_Cape_Peninsula_Dealing_with_the_inevitable">fire-dependent and fire-prone</a>. The Cape’s incredibly biodiverse fynbos plants need fire to survive and thrive. Fynbos animals have likewise adapted their life cycles to fire. For example, baby tortoises that hatch after the fire season with the first rains rely on the flush of green to survive.</p>
<p>Fynbos requires a burn every <a href="https://pdfs.semanticscholar.org/1dee/1185429d1ca8a7608e528a293559b55db436.pdf">12-15 years on average</a>, otherwise species can be lost. Fires at shorter intervals (for example, less than seven to eight years) would eliminate many shrub species, while longer intervals between fires (over 30 years) cause senescence and die-off.</p>
<p>For example, South Africa’s iconic proteas are threatened by too-frequent fires because they need time to <a href="http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000600005">build up seed reserves</a>. And sunbirds and sugarbirds are threatened because they <a href="https://www.researchgate.net/publication/225445942_Reduced_flower_visitation_by_nectar-feeding_birds_in_response_to_fire_in_Cape_fynbos_vegetation_South_Africa">require older fynbos as habitat</a>.</p>
<p>Fire frequency is not the only important factor. Season and weather conditions are also important. These affect fire intensity, which is important in stimulating germination of seeds stored in the soil. </p>
<h2>Risk factors</h2>
<p>Fire hazard is <a href="https://www.frames.gov/documents/behaveplus/publications/Countryman_1972_TheFireEnvironmentConcept_ocr.pdf">influenced by three factors</a>: fuel loads, the weather and an ignition source (such as lightning, cigarette butts or arson).</p>
<p>The danger of fires in the Cape region this season is therefore partly dependent on how the fynbos has been managed over the past few decades. Good management includes promoting natural fire regimes and maintenance of fire belts. </p>
<p>If we have managed fynbos well, an ignition point will not become a disaster.
Under what conditions might ignition prove dangerous? When there are high fuel loads with suitable fire weather, this can result in disastrously uncontrollable fires. </p>
<p>When do we get high fuel loads? In two scenarios: when fire has been suppressed in fynbos for too long, and when <a href="https://fireecology.springeropen.com/articles/10.1186/s42408-018-0001-0">alien trees</a> such as pines, wattle, hakea and gums have invaded fynbos.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296409/original/file-20191010-188797-1ek2jwt.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">Indigenous Fynbos burns in a bush fire next to the Atlantic Ocean in Misty Cliffs, Cape Town.</span>
<span class="attribution"><span class="source">EPA/Nic Bothma</span></span>
</figcaption>
</figure>
<h2>Areas of highest risk</h2>
<p>Given these factors, some areas of the Cape Peninsula constitute a higher fire hazard than others. The areas that <a href="http://www.photodestination.co.za/cape-aflame-cape-town-s-dance-with-fire.html">burned in a large fire in 2015</a> have lower fuel loads and thus pose little fire hazard. Areas that didn’t burn in the 2015 fire are a greater fire hazard.</p>
<p>The highest fire hazard of all would be the slopes above Kirstenbosch, Newlands and the Back Table (the back of Table Mountain), where fire has been <a href="https://www.ecologi.st/post/fire-shadows/">kept out</a> for over 40 years. Areas such as Cecilia and Tokai, on the urban edge of the southern suburbs of the city, with alien pine and gum plantations, are also a big hazard. </p>
<p>Given the magnitude of the fuel loads, ignition in these areas would likely result in a disastrous fire.</p>
<p>Fire weather is also important. Under perfect fire conditions, a fire would be unstoppable if it occurred in areas of high fuel loads. The <a href="http://www.auburn.edu/academic/forestry_wildlife/fire/weather_elements.htm">key weather drivers of fire hazard</a> include antecedent rainfall and soil moisture, temperature, relative humidity, wind speed and wind direction. These weather conditions play a role in the short lead-up to ignition, as well as when the fire is burning.</p>
<h2>Untangling natural variation and climate change</h2>
<p>There is also the issue of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5081606/pdf/pnas.201612926.pdf">anthropogenic climate change</a> – changes in climate brought about by human activities. </p>
<p>How might climate change affect fire hazard? The odds are good that this summer will be <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.4849">warmer than the average summer 20 years ago</a>. This is because global warming is making the average climate warmer by around <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/wcc.295">0.2°C per decade</a>. </p>
<p>But this is also true of recent preceding years, for example between 2015 and 2018. There is no evidence from a climatic point of view that this next fire season will have a higher hazard in terms of temperature than the past few years.</p>
<p>Most climate model projections agree that the Cape will <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/wcc.295">become drier in future</a>. But <a href="https://www.sajs.co.za/article/view/3952">observed trends up to now are insignificant and contradictory</a>. For example, a dry August and September may possibly leave vegetation this summer drier than in an average year. But, in fact, the Cape Town area is <a href="https://www.mdpi.com/2073-4441/9/11/876">much less dry than during the drought years of 2015-2017</a>.</p>
<p>When trying to understand anthropogenic climate change, we need to be able to separate it from natural variability. For example, if there is an active El Niño event, most regions of the world will be <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2014EO230013">warmer than normal</a>. To account for natural variability, we turn to seasonal forecasts.</p>
<p>Seasonal forecasts for this summer show varied results for temperature over the southwestern Cape. The <a href="http://www.weathersa.co.za/home/longrangeforecast">South African Weather Service</a> is suggesting a cooler than normal summer, and the <a href="https://www.ecmwf.int/en/forecasts/charts/catalogue/">European Centre</a> is indicating a warmer than average summer.</p>
<p>For rainfall this coming summer, where the occasional rain events might help reduce dryness in the fuel load, there is <a href="http://www.csag.uct.ac.za/2018/01/25/so-when-is-it-going-to-rain/">little skill</a> in seasonal forecasts. So it’s <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005GL023965">hard to say</a> whether a potential lack of rainfall during the summer will increase fire hazard.</p>
<p>In itself, this combination doesn’t suggest a significantly higher fire hazard next season than in previous years. Therefore there is no evidence to suggest that the next fire season in the Cape will be anything out of the ordinary. </p>
<p>Despite this, we should still be taking precautions.</p>
<h2>Precautions</h2>
<p>We suggest three actions: clear, manage and educate.</p>
<p>“Clear” refers to the removal of alien trees. Local residents can join alien clearing groups in their area. “Manage” refers to the need to support authorities on the Cape Peninsula – such as SANParks – to manage fynbos appropriately. This includes ensuring that, on average, 12-15 year prescribed burns happen. </p>
<p>And finally, education is needed to ensure that people understand climate variability versus climate change, as well as the relationship between fynbos and fires, so that future disasters can be avoided.</p><img src="https://counter.theconversation.com/content/125069/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alanna Rebelo receives funding for her postdoctoral research from the Danish International Development Agency (DANIDA).
Alanna Rebelo volunteers for the WESSA-affiliated Friends of Tokai Park community organisation. </span></em></p><p class="fine-print"><em><span>David Carlyle Le Maitre receives funding via contract research work as a Principal Researcher with the CSIR in Stellenbosch. He receives contract funding from various sources including the DEFF Natural Resources Managment Programmes and the Department of Environmental Affairs and Development Planning in the Western Cape.</span></em></p><p class="fine-print"><em><span>Mark New receives funding from the AXA Research Fund, the BNP Paribas Foundation's Climate Initiative, the International Development Research Centre, DANIDA and the National Research Foundation of South Africa, among others.</span></em></p><p class="fine-print"><em><span>Peter Johnston receives funding from the Water Research Commission and Australia Africa Universities Network.</span></em></p><p class="fine-print"><em><span>Petra Holden receives funding for her postdoctoral research from the Danish International Development Agency (DANIDA), the AXA Research Fund, and the BNP Paribas Foundation's Climate Initiative.</span></em></p><p class="fine-print"><em><span>Tiro Nkemelang receives funding from the AXA Research Fund.</span></em></p><p class="fine-print"><em><span>Tony Rebelo is affiliated with Friends of Tokai Park (a WESSA Friends group), Custodians of Rare and Endangered Wildflowers, SANParks Honorary Rangers, Western Leopard Toad Conservation Committee (chair), Botanical Society of South Africa, and is a researcher at the South African National Biodiversity Institute, Kirstenbosch, in the fields of Citizen Science, Restoration Ecology, Conservation Planning and Ecology. All my research funding, and intern support, is via SANBI.</span></em></p>The danger of fires in the Cape region this season is partly dependent on how the Fynbos has been managed over the past few decades.Alanna Rebelo, Postdoctoral researcher, Stellenbosch UniversityDavid Carlyle Le Maitre, Principal Researcher Ecosystem services assessment and mapping, Council for Scientific and Industrial ResearchMark New, Director, African Climate and Development Initiative, University of Cape TownPeter Johnston, Climate Scientist and Researcher, University of Cape TownPetra Brigitte Holden, Postdoctoral Research Fellow, University of Cape TownTiro Nkemelang, PhD student in African Climate Risk, University of Cape TownTony Rebelo, Scientist, South African National Biodiversity InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/993102018-07-04T09:15:35Z2018-07-04T09:15:35ZHow the land recovers from wildfires – an expert’s view<p>The apocalyptic images of desolate, scorched landscapes following the <a href="https://www.theguardian.com/uk-news/2018/jul/01/firefighters-from-seven-counties-fight-greater-manchester-moor-fires">wildfires in Greater Manchester and Lancashire</a> are hard to reconcile with the lush, picturesque moorland scenery that had existed just days before. While the <a href="https://www.theguardian.com/uk-news/2018/jun/27/saddleworth-moor-wildfire-army-called-in-to-tackle-fire">fight to extinguish these fires continues</a> – and <a href="https://www.independent.co.uk/news/uk/home-news/saddleworth-moor-fire-latest-updates-forecast-damage-manchester-a8421286.html">may do so for weeks</a> – our thoughts turn to the recovery of the affected area that now exceeds 2,000 hectares in size.</p>
<p>Words that have been used to describe the burnt areas in the media include “devastated”, “ravaged” and “barren” – but is this really the case? The question now is whether our moorlands, which are home to many rare and endangered species and play an important role in carbon and water storage, will be able to recover from this “relentless destruction”.</p>
<p>The full scale of the impact to wildlife and the moorland habitat will not be known until the blaze is out but some of the immediate effects are clear. Animals that could escape the flames, such as deer and mountain hares, have moved to more hospitable landscapes. But those with more limited mobility, for example small mammals, reptiles, amphibians and insects, may not have been so fortunate. </p>
<p>The timing has been particularly crucial for species of <a href="https://www.bbc.co.uk/news/science-environment-44643827">ground-nesting birds</a>, such as skylarks, meadow pipits, curlews and short-eared owls, whose nests and young are at risk of being burned. For plants, all vegetation above the ground will have been scorched and many seeds and root systems will have been destroyed by the heat. The fire may also be having effects on the soil – there have been reports of smouldering peat fires.</p>
<h2>Risk of extinction</h2>
<p>Severe fire can act as a steriliser, essentially resetting the successional clock (how an ecosystem progressively changes over time) in an area by reducing complex and established communities of fungi, microbes, plants and animals to bare soil. At extremes it can also heat and damage the soil’s structure and community of organisms, which may trigger irreversible erosion.</p>
<p>Of particular concern in these current fires is the burning and resultant loss of peat and its associated vegetation, which not only releases large quantities of greenhouse gases and accumulated pollutants (such as heavy metals) but also takes a long time to recover – peat forms at a rate of 0.5 to 1mm per year. As a consequence, the complex web of interactions between moorland species of vegetation is likely to take a long time to rebuild following such a severe fire, with some species possibly becoming locally extinct.</p>
<h2>Serious ecological consequences</h2>
<p>The influence of fire can also expand beyond the burnt area. Peatlands occur mainly in upland areas covering the headwaters of most major British rivers and, as such, fires can cause large amounts of organic carbon to be deposited into rivers. This may have significant <a href="https://www.journals.uchicago.edu/doi/full/10.1086/683426">negative effects</a> on river inhabitants.</p>
<p>Much of the scientific literature on the ecological effects of moorland fires focuses on small-scale, controlled fires. Such fires have been used to manage moorland for grouse shooting and may also be an effective conservation tool. For example, studies from five Peak District moors demonstrate that controlled fires are <a href="https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2664.2011.02052.x">important in maintaining plant diversity</a>. </p>
<p>The lack of controlled burning in the affected areas is suggested as a contributing factor to <a href="http://www.bbc.co.uk/news/amp/uk-england-manchester-44648348">the scale and intensity of the wildfires</a> with fuel loads having built up over time. The effects of severe, uncontrolled wildfires are less well understood but there is <a href="http://rstb.royalsocietypublishing.org/content/371/1696/20150342">growing evidence</a> that they can have very serious ecological consequences. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/225973/original/file-20180703-116143-1jt8p9b.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">Burnt out vegetation on the moors about Bolton, Greater Manchester.</span>
<span class="attribution"><span class="source">@PaulKeaveny</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Nature’s resilience</h2>
<p>But we must not to quickly write off the resilience of our moorland wildlife in the face of these fires. The earliest evidence of wildfires comes from <a href="https://pubs.geoscienceworld.org/gsa/geology/article-abstract/32/5/381/29429/charcoal-in-the-silurian-as-evidence-for-the?redirectedFrom=fulltext">420m years ago</a> and since then many species of plants and animals have developed ways to survive, regenerate and even take advantage of fire. Some species, such as <a href="https://nph.onlinelibrary.wiley.com/doi/full/10.1111/j.1469-8137.2012.04079.x">pine</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/21388378">banksia</a> trees, have gone so far as to become completely dependent upon fire to release their seeds and fulfil their life cycle.</p>
<p>In addition to natural fires, species from the moorlands of northern Europe have experienced frequent controlled burns for over 150 years. Moorland plants possess an array of strategies to persist through fire including re-sprouting from protected buds (for example, purple moor grass) and underground structures called rhizomes (such as bilberry), or regenerating from seeds (heather). </p>
<p>These survival mechanisms may come as a direct result of these human-driven management strategies. For example, heather seeds from fire managed heathlands <a href="http://rsbl.royalsocietypublishing.org/content/10/2/20131082.full">germinate more quickly when exposed to smoke</a> in comparison to those from other infrequently burnt habitats. As a result they are better able to make the most of the bare, nutrient-rich soil exposed by the fire. So the recovery of moorland vegetation on scorched land may be quicker particularly if assisted by patches of unburned vegetation.</p>
<p>It is the severity of these fires, which is yet unknown, that will be decisive to their ecological impact. Importantly, with upland fires becoming <a href="https://www.theguardian.com/world/2018/jun/29/more-saddleworth-style-fires-likely-as-climate-changes-scientists-warn">more frequent under climate change</a>, we must find a management solution, such as the use of regular burns to control fuel loads, that reduces the impact of wildfires and preserves these <a href="https://www.sciencedirect.com/science/article/pii/000632079400043P">internationally important ecosystems</a>.</p><img src="https://counter.theconversation.com/content/99310/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kimberley Simpson 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>How will important habitats recover from the wildfires which been blazing through moorland in northern England?Kimberley Simpson, PhD Student in Ecology, University of SheffieldLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/821852017-08-20T09:26:56Z2017-08-20T09:26:56ZGrowing more plants and trees can cut down the heat in Nigerian cities<figure><img src="https://images.theconversation.com/files/182436/original/file-20170817-28171-91a4q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Plants and trees cool themselves and the surrounding environment like this building in Paris, France. </span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Nigeria is regarded as a hot country. Average maximum temperature <a href="http://www.climatestotravel.com/climate/nigeria">can reach 38°C</a> - one of the hottest in sub Saharan Africa. In the last few years extreme heat and intense heatwaves have become a common experience in both rural and urban areas, showing that the country is getting hotter. This year, the Nigerian Meteorological Agency has <a href="http://www.vanguardngr.com/2017/03/nigerians-likely-experience-danger-heat-stress-2017-nimet/">warned</a> of an “above danger heat stress”.</p>
<p>These experiences are in line with <a href="http://ar5-syr.ipcc.ch/">projections</a> that the mean temperature of the planet is increasing, and expected to go on doing so. In Nigeria, the average air temperature is expected to rise by between 0.2 and 2.5°C over the next five decades, according to the <a href="https://www.researchgate.net/publication/229019531_General_overview_of_climate_change_impacts_in_Nigeria">UN’s Intergovernmental Panel on Climate Change</a>.</p>
<p>These increases can’t be overlooked. The effect is already being felt in cities which have developed what is known as <a href="http://www.sciencedirect.com/science/article/pii/S2352938517300381">“heat islands”</a>. These are urban areas that have higher temperatures than surrounding rural areas due to the fact that natural landscapes have been replaced by paved surfaces and buildings. </p>
<p>Some <a href="http://www.mdpi.com/2225-1154/3/4/775/htm">predict</a> that Nigerian cities may become too hot to live in.</p>
<p>Practical solutions are needed. One approach that’s been shown to work elsewhere is urban greening. This involves introducing trees and plants in places such as parks and gardens, streets, on walls and on top of roofs. By constantly releasing moisture into the atmosphere through their leaves, plants and trees cool themselves and the surrounding environment. This helps to reduce heat. This principle is well known and has been implemented in many European and <a href="http://www.sciencedirect.com/science/article/pii/S0169204610001234">North American cities</a>. </p>
<p>We <a href="http://www.sciencedirect.com/science/article/pii/S2212095513000084">studied</a> the temperatures inside and around two typical buildings in Akure, Nigeria. One of the buildings had trees around it while the other had none. The study was carried out for six months and spread across the two seasons (rainy and dry). It showed that tree shading had an impact on thermal conditions in buildings and their surroundings. </p>
<p>This evidence, alongside other research, shows that plants and trees need to be grown in the country’s cities. And everyone must play a part - individuals, households, communities, cities and states. </p>
<h2>Reducing temperatures and energy saving</h2>
<p>Our study showed that air temperature was higher and stayed that way for longer inside the building without vegetation, with indoor–outdoor temperature reaching a peak of 5.4°C for the unshaded building and 2.4°C for the tree-shaded one. The outdoor area around the tree-shaded building was cooler than around the unshaded one, irrespective of the season.</p>
<p>But the impact of the trees went beyond just the temperature. The cooler temperatures meant that there was less demand for indoor cooling like air-conditioners. </p>
<p>Two <a href="http://www.sciencedirect.com/science/article/pii/S0378778814004708">separate studies</a> done in Nigeria <a href="https://link.springer.com/article/10.1007/s12053-016-9449-4">show</a> that greening buildings can reduce the use of air-conditioning, leading to annual savings of about 34,500 NGN (US$218) in Akure and 17,255 NGN (US$162) in Owerri. These cities are in two different regions of Nigeria yet the results were similar.</p>
<p>Other studies support our research findings. A difference in the average <a href="https://www.ajol.info/index.php/ejesm/article/view/82353">temperature of 7.5°C</a> between spaces with trees and those without was recorded in Enugu, a city in South East Nigeria. In Abuja, researchers <a href="http://www.sciencedirect.com/science/article/pii/S2352938517300381">found</a> that bare surfaces and built-up areas had higher land surface temperatures while green surfaces maintained lower land surface temperatures. </p>
<p>Vertical greening systems like green walls in Lagos was found to have around 0.5°C reduction in <a href="http://www.sciencedirect.com/science/article/pii/S1877705815020986">temperature</a>. </p>
<h2>What must be done</h2>
<p>State and local governments have the main responsibility of introducing policies that would lead to more greening in Nigeria’s cities. In the last ten years <a href="https://www.pmnewsnigeria.com/2013/12/03/parks-and-gardens-development-the-lagos-example/">some states</a> and the Federal Capital Territory have <a href="http://fig.net/resources/proceedings/fig_proceedings/fig2010/papers/ts09e/ts09e_jibril_4638.pdf">built urban parks</a>. But much more needs to be done to significantly increase the amount of vegetation and green spaces in the country’s cities. Urban tree planting projects should be promoted on streets and beyond. </p>
<p>There should be programmes to plant trees in neighbourhoods and to create vegetated play parks, community gardens and other forms of green open spaces. Plants should also be planted in road setbacks and spaces within dual carriage ways. Vacant lots and derelict buildings can also be purposefully vegetated.</p>
<p>There should also be a push for gardens to be created – for food as well as aesthetic reasons – inside houses, on the roof or on the walls. Densely packed built environment in cities make space a challenge. But this can be overcome through plant growing techniques that use up little or no space. Good examples of vertical greening systems are <a href="https://www.youtube.com/watch?v=pzwUDz5Bifc">available in Mexico City</a>. </p>
<p>These examples provide proof that vegetation at the household and community level can directly influence temperature in the neighbourhood. We believe urban greening is a task that can, and must, be done.</p><img src="https://counter.theconversation.com/content/82185/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 organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Greening cities have a huge impact. The trees go beyond just lowering temperatures. They help decrease the demand for indoor cooling like air-conditioners saving money.Olumuyiwa Adegun, Lecturer, Department of Architecture, Federal University of Technology, AkureTobi Eniolu Morakinyo, Postdoctoral fellow at the Institute of Future Cities, Chinese University of Hong KongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/794192017-06-20T05:31:46Z2017-06-20T05:31:46ZLand clearing on the rise as legal ‘thinning’ proves far from clear-cut<figure><img src="https://images.theconversation.com/files/174592/original/file-20170619-770-h5c4tb.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A 'thinned' landscape, which provides far from ideal habitat for many species.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p><a href="http://scboceania.org/policystatements/landclearing/">Land clearing is accelerating across eastern Australia</a>, despite our <a href="http://www.publish.csiro.au/PC/PC17001">new research</a> providing a clear warning of its impacts on the Great Barrier Reef, regional and global climate, and threatened native wildlife. </p>
<p>Policies in place to control land clearing have been <a href="https://theconversation.com/queensland-moves-to-control-land-clearing-other-states-need-to-follow-58291">wound back across all Australian states</a>, with major consequences for our natural environment. </p>
<p>One of the recent policy changes made in <a href="https://www.qld.gov.au/environment/land/vegetation/codes/">Queensland</a> and <a href="http://www.environment.nsw.gov.au/vegetation/selfassess.htm">New South Wales</a> has been the introduction of self-assessable codes that allow landholders to clear native vegetation without a permit. These codes are meant to allow small amounts of “low-risk” clearing, so that landholders save time and money and government can focus on regulating activities that have bigger potential impacts on the environment. </p>
<p>However, <a href="http://www.wwf.org.au/ArticleDocuments/360/pub-accelerating-bushland-destruction-in-queensland-21mar17.pdf.aspx?Embed=Y">substantial areas of native forest are set to be cleared in Queensland under the guise of vegetation “thinning”</a>, which is allowed by these self-assessable codes. How did this happen?</p>
<h2>Thin on the ground</h2>
<p>Thinning involves the selective removal of native trees and shrubs, and is widely used in the grazing industry to improve pasture quality. It has been argued that thinning returns the environment back to its “<a href="https://publications.qld.gov.au/storage/f/2014-09-26T07%3A13%3A24.191Z/code-thickened-vegetation-in-the-brigalow-belt.pdf">natural state</a>” and <a href="http://www.abc.net.au/lateline/content/2015/s4462241.htm">provides better habitat for native wildlife</a>. However, the <a href="http://www.publish.csiro.au/bt/bt14137">science</a> supporting this practice is not as clear-cut as it seems.</p>
<p>Vegetation “thickening” is part of a natural, dynamic ecological cycle. Australia’s climate is highly variable, so vegetation tends to grow more in wetter years and then <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2005.00998.x/full">dies off during drought years</a>. These natural cycles of thickening and thinning can span 50 years or more. In most areas of inland eastern Australia, there is <a href="http://www.sciencedirect.com/science/article/pii/S0006320712005009">little evidence</a> for ongoing vegetation thickening since pastoral settlement.</p>
<p>Thinning of vegetation using tractors, blades and other machinery interrupts this natural cycle, which can make post-drought recovery of native vegetation more difficult. Loss of tree and shrub cover puts native wildlife <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0133915">at much greater risk from introduced predators like cats</a>, and aggressive, “<a href="http://onlinelibrary.wiley.com/doi/10.1111/ddi.12294/full">despotic</a>” native birds. Thinning reduces the diversity of wildlife by favouring a few highly dominant species that prefer <a href="http://www.publish.csiro.au/rj/rj05029">open vegetation</a>, and reduces the availability of old trees with hollows. </p>
<p>Many native birds and animals can only survive in vegetation that hasn’t been cleared for at least 30 years. So although vegetation of course grows back after clearing, for native wildlife it’s a matter of quality, not just quantity. </p>
<h2>Land clearing by stealth?</h2>
<p>Thinning codes in Queensland and New South Wales allow landholders to clear vegetation that has thickened beyond its “<a href="https://publications.qld.gov.au/storage/f/2014-09-26T07%3A13%3A24.191Z/code-thickened-vegetation-in-the-brigalow-belt.pdf">natural state</a>”. Yet there is little agreement on what the “natural state” is for many native vegetation communities.</p>
<p>Under the Queensland codes, <a href="https://www.dnrm.qld.gov.au/__data/assets/pdf_file/0020/342092/independent-review-sac-cardno.pdf">up to 75% of vegetation in an area can be removed without a permit</a>, and in New South Wales thinning can reduce tree density to a level that is <a href="https://biodiversity-ss.s3.amazonaws.com/Uploads/1494305298/LLS-Land-Management-Codes-exhibition-draft.pdf">too low to support natural ecosystems</a>.</p>
<p>All of this thinning adds up. Since August 2016, the Queensland government has <a href="https://data.qld.gov.au/dataset/vegetation-management-register-of-self-assessable-code-notifications">received self-assessable vegetation clearing code notifications</a> totalling more than 260,000 hectares. These areas include habitat for threatened species, and ecosystems that have already been extensively <a href="http://www.wwf.org.au/ArticleDocuments/360/pub-accelerating-bushland-destruction-in-queensland-21mar17.pdf.aspx?Embed=Y.">cleared</a>.</p>
<iframe src="https://www.google.com/maps/d/embed?mid=1L3revYC3nAXTLDCTlobq-0nbQ6c" width="100%" height="480"></iframe>
<p>It may be that the actual amount of vegetation cleared under thinning codes is less than the notifications suggest. But we will only know for sure when <a href="https://www.qld.gov.au/environment/land/vegetation/mapping/slats-reports/#slats-most-recent-reports">the next report on land clearing</a> is released, and by then it will be too late. </p>
<h2>Getting the balance right</h2>
<p>Vegetation policy needs to strike a balance between protecting the environment and enabling landholders to manage their businesses efficiently and sustainably. While self-regulation makes sense for some small-scale activities, the current thinning codes allow large areas of vegetation to be removed from high-risk areas without government oversight. </p>
<p>Thinning codes should only allow vegetation to be cleared in areas that are not mapped as habitat for threatened species or ecosystems, and not to an extent where only scattered trees are left standing in a landscape. <a href="https://theconversation.com/australia-needs-better-policy-to-end-the-alarming-increase-in-land-clearing-63507?sa=pg1&sq=land+clearing&sr=2">Stronger regulation is still needed</a> to reduce the rate of land clearing, which in Queensland is now <a href="http://www.abc.net.au/news/2017-06-19/land-clearing-rates-qld-need-to-be-lowered-new-study/8628524">the highest in a decade</a>. </p>
<p>Protecting native vegetation on private land reduces soil erosion and soil salinity, improves water quality, regulates climate, and allows Australia’s unique plants and animals to survive. Landholders who preserve native vegetation alongside farming provide essential services to the Australian community, and should be rewarded. <a href="https://theconversation.com/australia-needs-better-policy-to-end-the-alarming-increase-in-land-clearing-63507?sa=pg1&sq=land+clearing&sr=2">We need long-term incentives</a> to allow landholders to profit from protecting vegetation instead of clearing it.</p>
<p><a href="http://www.publish.csiro.au/PC/PC17001">Our research has shown</a> that Australian governments spend billions of dollars trying to achieve the benefits already provided by native vegetation, through programs such as the <a href="https://www.theguardian.com/australia-news/2016/feb/29/exclusive-land-clearing-surge-in-qld-set-to-wipe-out-direct-action-gains-report">Emissions Reduction Fund</a>, the <a href="http://www.nrm.gov.au/national/20-million-trees">20 Million Trees program</a> and <a href="http://www.nrm.gov.au/national/continuing-investment/reef-programme">Reef Rescue</a>. Yet far more damage is inflicted by under-regulated clearing than is “fixed” by these programs.</p>
<p>Imagine what could be achieved if we spent that money more effectively.</p><img src="https://counter.theconversation.com/content/79419/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>April Reside receives funding from NESP Threatened Species Recovery Hub. She sits on the Black-throated Finch Recovery Team and Birdlife Australia's Research and Conservation Committee. </span></em></p><p class="fine-print"><em><span>Anita J Cosgrove receives funding from the Australian Research Council. She is a member of the Black-throated Finch Recovery Team, BirdLife Australia and the Australian Conservation Foundation.</span></em></p><p class="fine-print"><em><span>Jennifer Lesley Silcock receives funding from the NESP Threatened Species Hub at the University of Queensland.</span></em></p><p class="fine-print"><em><span>Leonie Seabrook receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Megan C Evans receives funding from the National Environmental Research Programme Threatened Species Recovery Hub.</span></em></p>Legal vegetation ‘thinning’ is contributing to high rates of land clearing, potentially causing problems for threatened species and ecosystems.April Reside, Researcher, Centre for Biodiversity and Conservation Science, The University of QueenslandAnita J Cosgrove, Research Assistant in the Centre for Biodiversity and Conservation Science, The University of QueenslandJennifer Silcock, Post-doctoral research fellow, The University of QueenslandLeonie Seabrook, Landscape Ecologist, The University of QueenslandMegan C Evans, Postdoctoral Research Fellow, Environmental Policy, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/786272017-06-18T09:22:46Z2017-06-18T09:22:46ZAfrica’s got plans for a Great Green Wall: why the idea needs a rethink<figure><img src="https://images.theconversation.com/files/173386/original/file-20170612-10220-1jrelzo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">By the end of the 1990s, the idea of encroaching deserts had become difficult to defend.</span> <span class="attribution"><span class="source">IFRC/Flickr</span></span></figcaption></figure><p>Africa’s Great Green Wall, or more formally <a href="http://www.greatgreenwallinitiative.org/">The Great Green Wall for the Sahara and the Sahel Initiative</a>, is the intriguing but misleading name of an enormously ambitious and worthwhile initiative to improve life and resilience in the drylands that surround the Sahara. </p>
<p>The idea of a Great Green Wall has come a long way since its inception. Its origin goes back to colonial times. In 1927, the French colonial forester Louis Lavauden <a href="https://link.springer.com/chapter/10.1007/978-3-642-16014-1_8">coined the word desertification</a> to suggest that deserts are spreading due to deforestation, overgrazing and arid land degradation. In 1952 the English forester Richard St. Barbe Baker suggested that a <a href="https://wilmetteinstitute.org/the-man-of-the-trees-and-the-great-green-wall-a-bahais-environmental-legacy-for-the-ages/">“green front”</a> in the form of a 50km wide barrier of trees be erected to contain the spreading desert.</p>
<p>Droughts in the Horn of Africa and the Sahel from the 1970s onwards gave wings to the idea, and in 2007 the African Union approved the Great Green Wall Initiative. Many perceived it as a plan to build an almost 8,000km long, 15km wide, wall of trees across the African continent – from Senegal in the west to Djibouti in the east. </p>
<p>This plan faced a great deal of criticism. It led to a clearer vision being endorsed under the same name five years later when the African Ministerial Conference on Environment adopted a <a href="http://www.greatgreenwallinitiative.org/sites/default/files/publications/harmonized_strategy_GGWSSI-EN_.pdf">harmonised regional strategy</a>.</p>
<p>Can the vision ever come to fruition? </p>
<p>Only if there’s a ten-fold (at least) increase in pace so that the progress on the ground becomes consistent with lofty political ambitions. Sadly, the wall suffers from a major mismatch between ambition and effort. But that’s not to say it should be ditched. </p>
<h2>Why did the vision change?</h2>
<p><a href="http://www.csf-desertification.eu/combating-desertification/item/the-african-great-green-wall-project">Critics argue</a> that a desert is a healthy, natural ecosystem that shouldn’t be thought of as a disease. Nor, they argue, is it spreading like a disease. In fact, by the end of the 1990s, the idea of encroaching deserts had become <a href="https://www.iied.org/end-desertification">difficult to defend</a> against scientific evidence that climate variability was to blame. </p>
<p>Critics <a href="http://www.csf-desertification.eu/combating-desertification/item/the-african-great-green-wall-project">have also pointed out</a> that the vision of a barrier is counter-productive to the development objective as it draws attention to the perimeter of the land rather than to the land itself. To boost food security and support local communities it is better to focus on the wide field rather than its narrow edge. The development objective is important – an <a href="http://www.un.org/sustainabledevelopment/blog/2016/11/great-green-wall-initiative-offers-unique-opportunity-to-combat-climate-change-in-africa-un-agency/">estimated 232 million</a> people live in the general area of the Great Green Wall. </p>
<p>This led to the clarified vision keeping the wall in name, but it has been bent almost beyond recognition.</p>
<p>The wall is no longer seen as a narrow band of trees along the southern edge of the Sahara. The vision is now to surround the Sahara with a wide belt of vegetation – trees and bushes greening and protecting an agricultural landscape. The new vision engages all the countries surrounding it, including Algeria and others in North Africa, not just the 11 original sub-Saharan countries of the Sahel.</p>
<p>Thus, the Great Green Wall is no longer a wall. Nor is it great – not yet anyway.</p>
<h2>Unrealistic ambitions</h2>
<p>A simple analysis gives a clear indication of how difficult it will be to realise the Great Green Wall within agreed timelines. </p>
<p>A recent <a href="http://www.un.org/sustainabledevelopment/blog/2016/11/great-green-wall-initiative-offers-unique-opportunity-to-combat-climate-change-in-africa-un-agency/">analysis</a> by the Food and Agriculture Organisation suggests that 128 million hectares have a tree cover below the “better half” of comparable landscapes in the two aridity zones that straddle the 400 mm rainfall line around the Sahara. </p>
<p>If one assumes that half of this (65 million hectares, or 8% of the total area in these aridity zones) needs intervention, and that the United Nations’ <a href="http://www.un.org/sustainabledevelopment/development-agenda/">2030 Agenda for Sustainable Development</a> sets the target date for completion, then the Great Green Wall initiative should be treating an average of 5 million hectares per year (10 million hectares is the ambition to bring all lands up to the level of the better half). A less ambitious target date would be set by the African Union’s <a href="http://www.au.int/web/en/agenda2063">Agenda 2063</a> but even then an average treatment of 2 million hectares per year would be needed. </p>
<p>The actual intervention area is not known but is likely to be far less, no more than 200,000 hectares per year and probably less. At this pace, a century is an optimistic prediction of the time it will take to complete the Wall.</p>
<p>A massive increase in speed –- at least ten-fold –- is required if the Wall is to become great in our lifetime. More resources will clearly be needed but a ten-fold increase is unlikely. What to do?</p>
<h2>Re-greening options</h2>
<p>Many people assume that the wall can only be built only by planting trees. But tree planting is not always needed. Some of the less dry lands can be treated by techniques that rely on the capacity of the land to regreen itself – its ecological memory. </p>
<p>Floods and animals move seeds to places where they can sprout and root systems of former trees are sometimes capable of producing new shoots. Sprouting roots could live as the roots are already established – unlike newly planted seedlings. These could rapidly re-green a landscape, reducing the need for tree planting, as long as farmers protect them from fire and cattle. </p>
<p>This technique – known as farmer-managed natural regeneration – has proven to produce <a href="http://onlinelibrary.wiley.com/doi/10.1111/btp.12390/full">good results at low cost</a> in areas where the ecological memory is sufficient for sprouts to come up by themselves and where farmers have the right to use the trees once they get big. The potential to <a href="https://www.wri.org/sites/default/files/scaling-regreening-six-steps-success.pdf">scale it up</a> is significant.</p>
<p>But farmer-managed natural regeneration will not work everywhere. Other methods are needed too, such as digging half-moons (to capture water) and planting seedlings. Doing a better job of applying the right method to the right place may be the quickest and most feasible way to speed the making of the Great Green Wall.</p><img src="https://counter.theconversation.com/content/78627/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lars Laestadius is affiliated as a consultant with the United Nations Food and Agriculture Organisation. </span></em></p>Africa’s great green wall suffers from a major mismatch between ambition and effort. But that’s not to say it should be ditched altogether.Lars Laestadius, Adjunct Lecturer, Swedish University of Agricultural SciencesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/548982016-02-18T01:42:52Z2016-02-18T01:42:52ZRising extreme weather warns of ecosystem collapse: study<figure><img src="https://images.theconversation.com/files/111870/original/image-20160217-1240-d02eii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Extreme weather could trigger ecosystem collapse, including mass tree deaths. </span> <span class="attribution"><span class="source">Dead tree image from www.shutterstock.com</span></span></figcaption></figure><p>The world’s <a href="https://www.ipcc.ch/report/ar5/">climate is already changing</a>. Extreme weather events (floods, droughts, and heatwaves) are increasing as global temperatures rise. While we are starting to learn how these changes will affect people and individual species, we don’t yet know how ecosystems are likely to change. </p>
<p>Research published in Nature, using 14 years of NASA satellite data, shows eastern Australia’s drylands are among the <a href="http://nature.com/articles/doi:10.1038/nature16986">most sensitive ecosystems to these extreme events</a>, alongside tropical rainforests and mountains. Central Australia’s desert ecosystems are also vulnerable, but for different reasons.</p>
<p>As the world warms, this information can help us manage ecosystems and to anticipate irreversible changes or ecological collapse. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=262&fit=crop&dpr=1 600w, https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=262&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=262&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=329&fit=crop&dpr=1 754w, https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=329&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/111866/original/image-20160217-1261-1dhshr2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=329&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Maps created using satellite data to show which ecosystems are most sensitive to climate (orange) and least sensitive (green). Both could be worrying as the world warms.</span>
<span class="attribution"><a class="source" href="http://www.nature.com/nature/journal/vaop/ncurrent/full/nature16986.html">Seddon et al.</a></span>
</figcaption>
</figure>
<h2>Tipping points</h2>
<p>Ecological theory tells us that as ecosystems become unhealthy, they approach critical thresholds (also referred to as tipping points). The more unhealthy they become, the quicker they respond to disturbances. </p>
<p>Ecosystems that cross a critical threshold are transformed into new states, often with losses in biodiversity, exotic species invasions, and sudden forest die-off events. For example, over the past 10 years, ecosystems in the western US have experienced <a href="http://www.livescience.com/7637-tree-deaths-double-western-forests.html">large-scale tree deaths</a> and native, black grama grasslands have been transformed to the exotic, South African Lehmann lovegrass. </p>
<p>Farms and crops can be thought of as agricultural ecosystems, and they are highly sensitive to variations in climate. This means they are very challenging to manage for sustainable livestock and crop production under such intensifying conditions of sudden good and bad periods.</p>
<p>As humans we show weakened resistance when we are sick, and we become more susceptible to external conditions. Similarly, slower than normal ecosystem responses to external changes may also be indicative of an unhealthy ecosystem.</p>
<p>Both of these measures, fast and slow, are early warning signs for ecosystem collapse. </p>
<h2>Seeing ecosystems from space</h2>
<p>But how do we know if an ecosystem is going to collapse? Space offers a unique vantage point. The new research uses data from NASA’s Moderate Resolution Imaging Spectroradiometer (or MODIS) satellites. The satellites, orbiting roughly 900 km above Earth’s surface, measure things like snow and ice, vegetation, and the oceans and atmosphere.</p>
<p>The satellites measure ecosystem “greenness”, which indicates how much an ecosystem is growing. This is not too different from a farmer visually interpreting cues of plant health based on colour, except that satellites can have the capability to analyse colour in parts of the spectrum beyond our sensing capabilities.</p>
<p>The researchers developed a “Vegetation Sensitivity Index”, which showed how ecosystems responded to changes in climate. They particularly looked at changes in temperature, cloud cover, and rainfall. </p>
<p>One nice aspect of this research is that it specifically shows which climate component has the biggest role in changing ecosystems. For example changes to alpine meadows were attributed to warming temperatures, while tropical rainforests were very sensitive to fluctuations in solar radiation (or cloud cover).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/111867/original/image-20160217-1233-1823tsk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Australia’s dry ecosystems show dramatic changes between wet and dry. This is spinifex grassland during the dry. Spinifex covers around 20% of Australia’s land area.</span>
<span class="attribution"><span class="source">James Cleverly</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/111868/original/image-20160217-1261-dftvg4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mulga woodland during a wet period.</span>
<span class="attribution"><span class="source">James Cleverly</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Australia’s vulnerable ecosystems</h2>
<p>Eastern Australia’s dry woodlands and semi-arid grasslands, according to the study, are some of the most sensitive ecosystems to climate change, alongside tropical rainforests and alpine regions. The main factor in Australia is water. </p>
<p>This is in line with our <a href="http://onlinelibrary.wiley.com/doi/10.1002/2015JG003144/full">recent study</a> conducted in southeast Australia since 2000, which shows sudden, abrupt shifts in ecosystem function over many semi-arid ecosystems. This demonstrated the vulnerability of eastern Australian ecosystems to climatic variability and future extreme climatic events.</p>
<p>The new study also found central Australia’s deserts and arid lands show unusually slow responses to climate variability, which is concerning. Slower responses may be an early warning that these ecosystems are approaching a critical threshold before collapsing. </p>
<p>But this might also be an adaptation to the extreme climate variability these ecosystems already experience. The vegetation “knows” that the good, rainy times don’t last and therefore they may not invest in new growth that will later become a burden when drought returns.</p>
<h2>What does this mean for ecosystems?</h2>
<p>This research isn’t the end of the story. Although satellite data are valuable, they can’t tell us exactly what are the causes or mechanisms of ecosystem change. To do that, we need information on the ground, and consistent data over long periods of time is hard to come by. One example is Australia’s Terrestrial Ecosystem Research Network, or TERN. </p>
<p>The next step is to attribute the reasons why some systems appear to be more sensitive than others and more importantly, predict where and when the critical transitions will occur.</p>
<p>When forests, grasslands, and other ecosystems approach their critical thresholds, their resistance is weakened and they become highly susceptible to insects, pests, disease, species invasions, and mortality. One way to help ecosystems cope may be to reduce pressures on the land, such as recreation, harvesting and grazing.</p>
<p>If ecosystems collapse, we can mitigate some of the damage by helping wildlife and minimising soil erosion and runoff following tree deaths. But the most important thing is recognising that each ecosystem will behave differently; some may collapse, but others will survive.</p><img src="https://counter.theconversation.com/content/54898/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alfredo Huete receives funding from the Australian Research Council and the Terrestrial Ecosystem Research Network. </span></em></p><p class="fine-print"><em><span>Xuanlong Ma 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>Extreme weather will affect people and animals, as well as whole ecosystems. Research using satellites shows that ecosystems worldwide are vulnerable to collapse.Alfredo Huete, Professor, Plant Functional Biology & Climate Change, University of Technology SydneyXuanlong Ma, Research Associate in Remote Sensing of Environment, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/534932016-01-27T00:22:10Z2016-01-27T00:22:10ZThe planner’s new best friend: we can now track land-use changes on a scale of centimetres<figure><img src="https://images.theconversation.com/files/108918/original/image-20160121-9728-9hxd1e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The urban landscape is complex and ever-changing in cities such as Perth, but digital aerial photography can now monitor even the smallest changes.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Perth_Water,_Western_Australia.jpg">Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Cities and mine sites are complex spaces, which frequently change at a fine scale. This makes them hard to monitor. It is now possible, though, to adapt digital aerial photography to monitor changes as small as 10-20cm in both land use and vegetation in three dimensions.</p>
<p>Interested? Wondering whether that’s feasible? Here’s how you can do it cost-effectively.</p>
<p>Monitoring changes in land cover including vegetation has been routine since digital satellite imagery became available in the 1970s and 1980s. However, satellite images have traditionally been too coarse to monitor complex environments such as cities and mine sites, so aerial data is often acquired. In addition to needing sub-metre resolution, city buildings, mine pits and spoil dumps present challenges for automatically tracking change.</p>
<p>Analogue (film) imagery has been used for aerial monitoring long after digital photographers replaced film in hand-held cameras. This is partly because changing large programs with multiple users is risky.</p>
<p>About ten years ago the authors started working with Landgate, the Western Australian government agency responsible for photographing Greater Perth. Our aim was to see if the advantages of satellite monitoring could be incorporated into Landgate’s annual aerial photograph capture to detect changes in land use and vegetation condition at the sub-metre level. </p>
<h2>How is it done?</h2>
<p>As well as recording red, green and blue bands of light, a near infra-red band was included because vegetation health is best measured at this wavelength. The elevation of the ground, buildings and trees is estimated each time, with a similar resolution as the pixel size making the imagery three-dimensional. Being digital, it is easy to count pixels to quantify changes.</p>
<p>Digital data allows changes over time to be measured with much greater accuracy and efficiency than when comparing film images. </p>
<p>It requires, though, that the images be captured using a standard approach. Standardised images ensure that a change in digital reflectance represents a real change and not a change in the atmosphere, sun angle, camera type or a shadow. Each image also needs to be very accurately aligned.</p>
<p>Reflectance targets were placed on the ground to ensure images were standardised during the acquisition as well as between years. </p>
<p>After trials in 2006 and 2007, summer images were chosen. This was because these met most of the requirements of the consortium of 13 government agencies and non-government organisations that guided the transition from analogue to digital.</p>
<p>Summer is a time when un-irrigated plants are most stressed. This enables monitoring of soil water deficits, groundwater-dependent vegetation and an assessment of irrigation efficiency at the individual-sprinkler scale. There is also less cloud and the impact of recent rainfall is less evident, given that the capture can take several weeks. To limit shadows, capture times were restricted to two hours each side of solar noon.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1065&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1065&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1065&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1338&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1338&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108818/original/image-20160121-9728-cvxp2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1338&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 area of Greater Perth covered by the digital aerial photography each summer.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The area covered by the digital aerial photography each summer (see figure at right) extends beyond that needed to update street directories. It includes groundwater catchments, pine plantations and peri-urban horticulture. This coverage also enabled us to monitor disease impacts on native trees of interest to the consortium.</p>
<p>Technical details can be found in <a href="http://www.tandfonline.com/eprint/rNsUJ4vf7MiaDDbKaSIb/full">an article</a> in the International Journal of Digital Earth and on the <a href="http://urbanmonitor-beta.landgate.wa.gov.au/project.php">Urban Monitor website</a>. The website includes a <a href="http://urbanmonitor-beta.landgate.wa.gov.au/home.php">beta test site</a> of vegetation products maintained by Landgate.</p>
<h2>Many uses, and counting…</h2>
<p>The method has been applied to:</p>
<p>1) Monitoring <a href="http://www.planning.wa.gov.au/publications/7216.asp">tree canopy cover</a> in the Greater Perth region for state and local government planners to assess habitat loss and an increase in the urban heat island.</p>
<p><img src="https://lh4.googleusercontent.com/bjTQfzkXrzJ0rMNIvO77ZpcdimxcIb_MQeyfOGzVnJEpAp8UXQIyBIIcuW-K5y_97F-iU0YE9v_IB2Xc-uYre9h1sfuhS-rYp2UdyKejvMGszqaH4y9HtyP_GrXcqzBoLc7W73pPq8bXELLA" alt=""></p>
<p>2) Identifying tall trees (even those in low-elevation areas) of importance to roosting birds such as the endangered Carnaby Cockatoos for the <a href="https://www.environment.gov.au/resource/urban-monitor-enabling-effective-monitoring-and-management-urban-and-coastal-environments">Perth Peel Regional Sustainability Plan</a>. In the image below, tree heights are shown in increasingly “hot” colours, displayed with a sun-shaded elevation model in grey for unvegetated areas. A digital <a href="http://online.wr.usgs.gov/ngpo/doq/doq_basics.html">orthophotograph</a> of the area is shown on the left.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=669&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=669&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=669&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=841&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=841&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108830/original/image-20160121-9746-1tx05wv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=841&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tree heights are shown in increasingly ‘hot’ colours in a sun-shaded elevation model (right) of the area in the digital orthophotograph on the left.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=760&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=760&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=760&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=955&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=955&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108912/original/image-20160121-9725-zngwfw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=955&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 image shows vegetation losses in red, growth in green and no change in yellow.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>3) Tree and bush decline in native vegetation in urban areas. The image at right shows vegetation losses in red, growth in green and no change in yellow. Non-vegetated areas are uncoloured.</p>
<p>4) Estimating the effect of urbanisation on urban water balances, especially runoff and recharge. Being three-dimensional, the images can identify where water will flow in new urban catchments.</p>
<p>5) The identification of blocks of land that have been built upon for urban infill planning (shown as red blocks in the image below).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=351&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=351&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=351&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=442&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=442&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108913/original/image-20160121-9769-1wfyfg4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=442&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Blocks of land that been built on (marked in red) can easily be identified to monitor urban infill.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>6) Drying of groundwater-fed wetlands in the Perth Peel region.</p>
<p>7) The impact of mine or coal seam gas developments on vegetation and runoff. The example below shows predicted flow paths and accumulations of water in a rural landscape after development of coal seam gas sites.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=160&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=160&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=160&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=201&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=201&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108914/original/image-20160121-9763-1cfenec.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=201&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Predicted flow paths and accumulations of water following development of coal seam gas sites.</span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The scale of the imagery is especially suited to local government and mining companies reporting to regulators, as it can help separate mine impacts from climate, fire, grazing or other disturbances.</p>
<p>Readers will probably identify further uses for the method – something that we have experienced whenever we give talks on its application.</p>
<p>In the Greater Perth region, digital acquisition using monitoring standards has replaced analogue capture, so it is routine with limited additional costs for acquisition. Not all datasets have been fully processed but they are archived for later reference as funds and needs arise. The data are expected to become increasingly valuable over time because they cannot be acquired retrospectively.</p>
<p>In time it is anticipated that Urban Monitor products similar to <a href="http://www.landmonitor.wa.gov.au/">Land Monitor</a> will be made available on the Landgate website. Land Monitor has used interpreted satellite imagery to provide change products to West Australian natural resource management agencies for more than 15 years for an annual cost of about $80,000. </p>
<p>This shows that good monitoring need not be expensive if thoughtful acquisition methods are used and products are developed to meet multiple user needs.</p><img src="https://counter.theconversation.com/content/53493/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Don McFarlane is a research scientist with the CSIRO; he receives funding from the Australian government. The research referred to in this article was funded by the Australian government and carried out in collaboration with several West Australian government departments including Landgate, which is responsible for the collection of spatial data in WA. </span></em></p><p class="fine-print"><em><span>Peter Caccetta is a research scientist with the CSIRO; he receives funding from the Australian government. The research referred to in this article was funded by the Australian government and carried out in collaboration with several West Australian government departments including Landgate, which is responsible for the collection of spatial data in WA. </span></em></p>Constant, complex changes in cities and mine sites are hard to monitor. Drawing on digital aerial photography, it’s now possible to track land-use and vegetation changes in areas as small as 10-20cm.Don McFarlane, Research Scientist; Groundwater Hydrology Team Leader, CSIROPeter Caccetta, Research Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/59952012-03-22T18:41:48Z2012-03-22T18:41:48ZHunters, not climate change, killed giant beasts 40,000 years ago<figure><img src="https://images.theconversation.com/files/8907/original/34z9kbnm-1332417435.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Diprotodon optatum, a marsupial mega-herbivore sometimes known as the Giant Wombat or the Rhinoceros Wombat, grew to three metres in length and two metres in height. Its closest surviving relatives are the wombat and the koala.</span> <span class="attribution"><span class="source">Peter Murray</span></span></figcaption></figure><p>The first Australians hunted giant kangaroos, rhinoceros-sized marsupials, huge goannas and other megafauna to extinction shortly after arriving in the country more than 40,000 years ago, new research claims.</p>
<p>A team of scientists from six universities say they have put an end to the long-running debate about the cause of the sudden disappearance of giant vertebrates from the Australian ecosystem, and the dramatic change to the landscape that followed.</p>
<p>Soon after the beasts disappeared, there was a rapid shift in vegetation across Australia. Once covered by patches of rainforest separated by areas of open grassland, it was soon smothered by eucalypt forest, the researchers say. </p>
<p>The change was caused by a decrease in consumption of plant material by large herbivores, which allowed forest to spread and also resulted in a build-up of dry fuel for bushfires.</p>
<p>In the past 100,000 years, many of the largest animals on Earth became extinct. The reasons remain contentious. In recent years, some scientists have argued that habitat loss through climate change or fire was the killer blow.</p>
<p>But the latest argument, published today in Science, refutes this.</p>
<p>Research leader Chris Johnson, from the University of Tasmania School of Zoology, said the team solved the mystery of the disappearance of Australia’s megafauna by using a method of tracking large herbivores through time by counting the spores of fungi in their dung.</p>
<p>Professor Johnson said the biggest herbivores - “rhino-sized wombat-like marsupials called Diprotodons, giant kangaroos, a goanna bigger than the living Komodo dragon, a giant goose twice the size of the emu and many others” - produced vast quantities of dung, and that there were special fungi that lived in it. </p>
<p>“The spores of these fungi can be preserved in sediments in swamps and lakes,” Professor Johnson said. “As those sediments accumulate over time, they create a historical record of the abundance of very large herbivores in the environment.</p>
<p>"Pollen and charcoal particles are trapped in the same sediments, so that it is possible to match up the history of abundance of large herbivores with changes in vegetation and fire. Then, radiocarbon can be used to date these things.”</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1138&fit=crop&dpr=1 600w, https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1138&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1138&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1430&fit=crop&dpr=1 754w, https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1430&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/8908/original/rm49j4gf-1332417844.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1430&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sthenurus, the giant kangaroo, grew up to three metres in length, or about twice as big as the modern kangaroo.</span>
<span class="attribution"><span class="source">Peter Murray</span></span>
</figcaption>
</figure>
<p>Professor Johnson said the research focussed largely on a swamp called Lynch’s Crater in northeast Queensland, where the sediment record reaches back to 130,000 years ago. </p>
<p>“It showed that the abundance of large mammals was stable until just before 40,000 years ago, when it suddenly crashed.</p>
<p>"This rules out climate change as a cause of extinction, as there were several periods of climate drying before the extinction and they had no effect on abundance. And when the animals did go extinct, the climate was stable. </p>
<p>Habitat change could not have been responsible for the loss of the large marsupsials, because the grassy forest expanded only after the spores abruptly declined.</p>
<p>"But the extinctions followed very soon after the time that people arrived in the region - so it seems that people did it,” Professor Johnson said.</p>
<p>“Our study didn’t directly address how people caused extinction, but the most likely mechanism is hunting. Quite a bit of other circumstantial evidence suggests that.”</p>
<p>The results also show that the extinctions were quickly followed by massive ecological change.</p>
<p>Gavin Prideaux, a lecturer in vertebrate palaeontology in the School of Biological Sciences at Flinders University, said the research was an important contribution to the understanding of what happened “when 90% of our large terrestrial species disappeared, depriving us of the sight of giant short-faced kangaroos, marsupial "lions”, giant horned tortoises and herds of Diprotodons meandering through the outback.“</p>
<p>The research team had presented compelling data in a field of inquiry that "aches under the strain of opinion pieces and the tired reworking of published data … The timing of the inferred extinction coincides with early human presence in the region, but not with significant climatic change.”</p>
<p>This supported a mounting number of studies that have argued that climate change was not primarily responsible for extinctions in other parts of the continent, Dr Prideaux said.</p>
<p>John Alroy, a Future Fellow in the Department of Biological Sciences, Faculty of Science at Macquarie University, said the new research put all debate over the matter to rest. “The key new data are the spore counts, and in combination with the charcoal and rainforest pollen data they tell the whole story,” Dr Alroy said. “There is simply no reasonable way to argue with the authors’ conclusions.”</p>
<p>But Judith Field, a Senior Research Fellow in the School of Biological, Earth and Environmental Sciences at The University of New South Wales, said the argument was flawed for several reasons.</p>
<p>Chief among these was the claim by the authors that climate was stable through the period in question - “the opposite is generally accepted”, Dr Field said - and the unproven assumption that megafauna were so abundant that their disappearance would have triggered a drastic change in vegetation.</p>
<p>“The facts of the matter are that most megafauna were extinct nearly 100,000 years before human arrival and there is no evidence for any particular time period to be significant in terms of faunal extinctions.”</p>
<p>Dr Field added that there was no evidence from archaeological sites that humans hunted megafauna. She said the earliest evidence for human occupation in northeast Queensland suggested their populations were small.</p><img src="https://counter.theconversation.com/content/5995/count.gif" alt="The Conversation" width="1" height="1" />
The first Australians hunted giant kangaroos, rhinoceros-sized marsupials, huge goannas and other megafauna to extinction shortly after arriving in the country more than 40,000 years ago, new research…Justin Norrie, EditorLicensed as Creative Commons – attribution, no derivatives.