tag:theconversation.com,2011:/uk/topics/photosynthesis-388/articlesPhotosynthesis – The Conversation2024-03-11T12:25:42Ztag:theconversation.com,2011:article/2229722024-03-11T12:25:42Z2024-03-11T12:25:42ZWhy do trees need sunlight? An environmental scientist explains photosynthesis<figure><img src="https://images.theconversation.com/files/578432/original/file-20240227-20-s7p24d.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2048%2C1364&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The reason trees need sunlight is the same reason their leaves are green.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/scottb211/10108377914/"> Scottb211/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<p><strong>Why do trees need sunlight? – Tillman, age 9, Asheville, North Carolina</strong></p>
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<p>Trees need sunlight for the same reason you need food. The energy from the Sun’s rays is a crucial ingredient in how plants make their own food that helps them power all their cells. Since trees don’t harvest or hunt food, they have to produce their own. The way they make their food is a unique and important chemical process called photosynthesis.</p>
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<a href="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="honey-comb pattern of rings each containing many small green spheres" src="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=510&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=510&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=510&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Chlorophyll is what makes leaves green.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Plagiomnium_affine_laminazellen.jpeg">Kristian Peters-Fabelfroh/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<h2>What is photosynthesis?</h2>
<p>The cells in plants and all other living things have microscopic components called <a href="https://www.genome.gov/genetics-glossary/Organelle">organelles</a>. One type of organelle in plant cells is the chloroplast, and it contains the <a href="https://www.kidzone.ws/science/lessons/pigments.html">pigment</a> chlorophyll, which is what makes leaves green. When chlorophyll receives sunlight, it starts the <a href="https://education.nationalgeographic.org/resource/photosynthesis">photosynthesis</a> reaction.</p>
<p>The name photosynthesis comes from the ancient Greek words “photo,” which means light, and “synthesis,” which means to make. During this food-making process, plants take carbon dioxide from the air and water from the ground, and with the energy from sunlight, make glucose. Glucose is a very simple type of sugar. Because it is a simple compound, it is simple to make.</p>
<p>Most of the time, photosynthesis occurs in leaves, and leaves take in sunlight to make food. There are some special plants, though, that actually absorb sunlight on their stems. Some of these include cactuses like the balloon-shaped <a href="https://www.gardenia.net/plant/echinocactus-grusonii-golden-barrel-cactus">golden barrel cactus</a>, the spiky <a href="https://huntington.org/educators/learning-resources/spotlight/cylindropuntia-munzii">Munz’s Cholla</a> and the paddle-shaped <a href="https://huntington.org/educators/learning-resources/spotlight/opuntia-ficus-indica">prickly pear</a>. Some plants even have roots that can photosynthesize, like the rare palm <em><a href="https://huntington.org/educators/learning-resources/spotlight/cryosophila-albida">Cryosophila albida</a></em>.</p>
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<a href="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphic diagram of a plant showing sun, soil, roots, leaves and a flower" src="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=755&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=755&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=755&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sunlight gives plants the energy to turn water and carbon dioxide into carbohydrates – the food their cells need to live and grow.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Photosynthesis_en.svg">At09kg/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<h2>Photosynthesis is billions of years old</h2>
<p>Photosynthesis evolved more than <a href="https://doi.org/10.1104%2Fpp.110.161687">3.5 billion years ago</a>. Initially, only single-celled organisms, kind of like today’s algae, could make sugar this way. Oxygen is a waste product from the photosynthesis process, and over time, these single-celled organisms released enough oxygen to change the Earth’s atmosphere. Ultimately, we and all other animals needed this to happen to be able to live and breathe. </p>
<p>Over time, aquatic plants developed, and gradually plants <a href="https://doi.org/10.1126/science.aat3642">moved to land</a> around 500 million years ago to better access their most vital resource: sunlight. Plants eventually got taller by around <a href="https://doi.org/10.1126/science.aar2986">350 million years ago</a>. This is when the first tree evolved, which grew up to 150 feet tall. These trees looked like the evergreen trees we see today – sort of like pines, firs and spruce. And about 125 million years ago, trees that looked like the maples, oaks and beech trees we see today shared the landscape when <a href="https://new.nsf.gov/news/dinosaur-age-fossils-provide-new-insights-origin">dinosaurs ruled the Earth</a>.</p>
<h2>Not just good for plants</h2>
<p>The Sun provides energy for the Earth. However, we humans are not capable of taking in the sun directly and using it to power our bodies. So how do we make use of the Sun’s energy? Plants do it for us.</p>
<p>Plants take in that energy and make food for us and other animals to eat and oxygen for us to breathe. We wouldn’t exist without plants and photosynthesis.</p>
<p>Like the ancient tiny single-celled organisms from 3.5 billion years ago, some microorganisms today use photosynthesis. Specifically, the algae that you might see living on top of lakes and the ocean do. Chlorophyll is why algae is green. </p>
<p>There are <a href="https://news.asu.edu/20191114-asu-study-shows-some-aquatic-plants-depend-landscape-photosynthesis">aquatic plants</a> that use sunlight to grow. They typically make use of less sunlight because sunlight does not travel well through water.</p>
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<span class="caption">Some plants can do photosynthesis underwater, where there is less sunlight.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/chesbayprogram/32446887586/">Chesapeake Bay Program/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
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<p>In addition, there are a very few animals that can photosynthesize. The <a href="https://doi.org/10.1038/nature.2012.11214">pea aphid</a> uses pigment to harvest sunlight to make energy. The <a href="https://phys.org/news/2011-01-physicists-outer-shell-hornet-harvest.html">Oriental hornet</a> uses a pigment in its exoskeleton to make energy from sunlight. The <a href="https://www.nationalgeographic.com/animals/article/solar-powered-photosynthetic-sea-slugs-in-decline-news">emerald-green sea slug</a> eats algae and then incorporates chlorophyll from the algae into its body to photosynthesize. Because of this strategy, the sea slug can go nine months without eating. </p>
<p>So the answer to this question – why do trees need sunlight – is to make their food. And thanks to trees and other plants turning sunlight into their food, most of the rest of the living things on Earth get to eat, too!</p>
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<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/222972/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rebekah Stein does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Trees – and all plants – harvest sunlight to gain the energy they need to live and grow.Rebekah Stein, Assistant Professor of Environmental Science, Quinnipiac UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1962262024-01-03T13:19:09Z2024-01-03T13:19:09ZHow scientists are helping plants get the most out of photosynthesis<figure><img src="https://images.theconversation.com/files/563630/original/file-20231205-15-2tk9l4.jpg?ixlib=rb-1.1.0&rect=5%2C5%2C3860%2C2579&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/detail-leaf-backlit-showing-ribs-veins-96544981">italianestro/Shutterstock</a></span></figcaption></figure><p>Photosynthesis is the starting point for almost every food chain, sustaining most life on Earth. You would be forgiven, then, for thinking nature has perfected the art of turning sunlight into sugar. But that isn’t exactly true. If you struggle with life goals, it might reassure you to know even plants haven’t yet reached their full potential.</p>
<p>Every evolved trait is a trade-off between the benefit it provides and its <a href="https://www.journals.uchicago.edu/doi/full/10.1086/717897">cost in energy</a>. The plants we domesticated for food are only as good at converting sunlight to sugar as they had to be to survive and reproduce. From a given amount of sunshine, most plants convert less than 5% of that <a href="https://bigthink.com/the-future/artificial-photosynthesis-improve/">light</a> energy into biomass, and under some conditions, less than 1%. </p>
<p>We now have the knowledge and the tools to maximise photosynthesis in a range of food crops – but scientists aren’t just studying how we help plants become better at photosynthesis out of curiosity. Climate change-driven weather such as drought and flooding is destroying crops and <a href="https://www.nature.com/articles/s43017-023-00491-0">threatening crop yields</a> around the world. This research is about making sure we can grow enough food to feed ourselves.</p>
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<img alt="" src="https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?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">
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<p><em>Many people think of plants as nice-looking greens. Essential for clean air, yes, but simple organisms. A step change in research is shaking up the way scientists think about plants: they are far more complex and more like us than you might imagine. This blossoming field of science is too delightful to do it justice in one or two stories.</em> </p>
<p><em><a href="https://theconversation.com/topics/plant-curious-137238?utm_source=TCUK&utm_medium=linkback&utm_campaign=PlantCurious2023&utm_content=InArticleTop">This article is part of a series, Plant Curious</a>, exploring scientific studies that challenge the way you view plantlife.</em></p>
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<p>Plants such as wheat sometimes mistakenly make a toxic substance called <a href="https://www.sciencedirect.com/topics/chemistry/2-phosphoglycolate">2-phosphoglycolate</a> which then has to be recycled inside the plant, costing it energy. Scientists call this <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/photorespiration">photorespiration</a>. It happens when an enzyme crucial to the photosynthesis process, <a href="https://www.sciencedirect.com/science/article/abs/pii/S0981942808000041">rubisco</a>, mistakenly latches on to an oxygen molecule instead of carbon dioxide.</p>
<p>Rubisco makes this mistake up to 40% of the time. It happens because there is now a lot more oxygen in the atmosphere than in the past, put there by the very first photosynthesisers, <a href="https://www.britannica.com/science/blue-green-algae">cyanobacteria</a> – microscopic organisms found in water. Rising temperatures cause more photorespiration too.</p>
<p>If we could prevent this mistake, it would leave plants more energy for photosynthesis. </p>
<h2>Capturing sunlight</h2>
<p>Our research project, <a href="http://www.photoboost.org/">PhotoBoost</a>, is looking at how to create a kind of internal bypass that reduces photorespiration in rice and potato plants, two of the world’s most important crops. </p>
<p>In the same way a coronary bypass diverts blood around narrow or clogged arteries in humans, the photorespiratory bypass gives plants the genetic tools they need to minimise rubisco’s mistake. Genes from cyanobacteria make this and other photosynthetic improvements possible because they host an array of enzymes for better sunlight management.</p>
<p>Other researchers are looking to plants such as maize, which have evolved their own means of dealing with photorespiration, as a source of inspiration – and genes – for <a href="https://www.ox.ac.uk/news/2017-10-19-breakthrough-efforts-supercharge-rice-and-reduce-world-hunger">rice</a>.</p>
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<img alt="Leafy green shoots growing out of well tilled soil, sun setting in the background" src="https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563631/original/file-20231205-19-lrhpyi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">These plants may not be making the most of photosynthesis.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sapling-mung-bean-agriculture-garden-light-1616176942">Lamyai/Shutterstock</a></span>
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<p>We’re also improving the speed at which plants respond to changes in light intensity, as this <a href="https://www.science.org/doi/10.1126/science.aai8878">affects photosynthesis</a> too. Plants shut off their photosynthetic machinery if they get too much sun (when light is more intense), after which they can be slow to restart photosynthesising when it gets cooler again – for example, when clouds roll over.</p>
<p>A research group in the US recently showed that speeding up this photoprotection process in soybean can lead to a <a href="https://www.science.org/doi/10.1126/science.adc9831">33% increase</a> in seed yield.</p>
<p>On PhotoBoost, we’re talking to researchers, agronomists and farmers all around the world to understand how to match the needs of society with this new frontier in plant science. According to Elizabete Carmo-Silva and Ana Moreira Lobo, colleagues at Lancaster University: “Climate change, declining yields and water stress constitute major challenges for food production this century.”</p>
<p>Their team investigates plant responses to light and temperature, paying particular attention to the rubisco enzyme. Higher yield is perhaps the most obvious gain from improving photosynthesis, but it will also help make plants more resilient to drought and heat stress.</p>
<h2>New tools</h2>
<p>A new tool in the crop breeder’s arsenal, <a href="https://pubmed.ncbi.nlm.nih.gov/24157548/">gene editing</a>, allows scientists to turn genes on and off, testing the effect they have on plant performance. Once we know their function, these genes can be suppressed, promoted or, as has been done in commercial crops <a href="https://www.fda.gov/food/agricultural-biotechnology/science-and-history-gmos-and-other-food-modification-processes#:%7E:text=1994%3A%20The%20first%20GMO%20produce,safe%20as%20traditionally%20bred%20tomatoes.">since the 1990s</a>, introduced through genetic modification.</p>
<p>At the Universidade Nova de Lisboa in Portugal, Nelson Saibo and Isabel Abreu told us the tools that plant breeders have are more “fine tuners” these days. Their team is using gene editing to improve photosynthesis in rice.</p>
<p>The potato farmers we recently spoke to in the east of England saw greater photosynthesis efficiency as a route to freeing up land for nature – for example, planting trees on ancient forest sites or restoring peatland in the Fens – as more efficient plants mean you need less of them to give the same crop yield. Their major concern was whether major UK retailers would be <a href="https://www.dailymail.co.uk/news/article-9276737/Co-op-British-supermarket-reject-GM-crops-animals-without-strict-assessments.html">willing to champion</a> genetically engineered crops.</p>
<p>As well as Photoboost, the European Union is funding other photosynthesis programmes through the <a href="http://gain4crops.eu/">Gain4crops</a> (sunflower) and <a href="https://www.capitalise.eu/crop-improvement/">Capitalise</a> (tomato, maize and barley) projects. Improving photosynthesis isn’t a silver bullet for many of the agricultural problems we face. But combining knowledge and new tools will help us get the most out of light.</p><img src="https://counter.theconversation.com/content/196226/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Menary receives funding from the European Union</span></em></p><p class="fine-print"><em><span>Sebastian Fuller receives funding from the European Commission and the UK National Institute for Health and Care Research </span></em></p><p class="fine-print"><em><span>Stefan Schillberg receives funding from the European Union</span></em></p>Plants aren’t always as good at photosynthesis as you might think. Our research project wants to help them.Jonathan Menary, Postdoctoral Researcher, Centre for Tropical Medicine and Global Health, University of OxfordSebastian Fuller, Researcher of Implementation Science, University of OxfordStefan Schillberg, Executive Director, Fraunhofer IMELicensed as Creative Commons – attribution, no derivatives.tag: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>
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</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>
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</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>
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</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/2109972023-10-23T12:25:38Z2023-10-23T12:25:38ZA layered lake is a little like Earth’s early oceans − and lets researchers explore how oxygen built up in our atmosphere billions of years ago<figure><img src="https://images.theconversation.com/files/542374/original/file-20230811-17-9wl0g5.jpeg?ixlib=rb-1.1.0&rect=0%2C12%2C4031%2C2692&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers sample water from various layers to analyze back in the lab.</span> <span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Little Deming Lake doesn’t get much notice from visitors to <a href="https://www.dnr.state.mn.us/state_parks/park.html?id=spk00181#homepage">Itasca State Park</a> in Minnesota. There’s better boating on nearby Lake Itasca, the headwaters of the Mississippi River. My colleagues and I need to maneuver hundreds of pounds of equipment down a hidden path made narrow by late-summer poison ivy to launch our rowboats.</p>
<p>But modest Deming Lake offers more than meets the eye for <a href="https://scholar.google.com/citations?user=QopCtZ4AAAAJ&hl=en&oi=ao">me, a geochemist</a> interested in how oxygen built up in the atmosphere 2.4 billion years ago. The absence of oxygen in the deep layers of Deming Lake is something this small body of water has in common with early Earth’s oceans.</p>
<p>On each of our several expeditions here each year, we row our boats out into the deepest part of the lake – over 60 feet (18 meters), despite the lake’s surface area being only 13 acres. We drop an anchor and connect our boats in a flotilla, readying ourselves for the work ahead.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Smooth lake with boats in the distance against woodsy shoreline" src="https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554300/original/file-20231017-27-mjcpvk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Researchers’ boats on Deming Lake.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Deming Lake is <a href="https://www.worldatlas.com/articles/what-is-a-meromictic-lake.html">meromictic</a>, a term from Greek that means only partially mixing. In most lakes, at least once a year, the water at the top sinks while the water at the bottom rises because of wind and seasonal temperature changes that affect water’s density. But the <a href="https://eartharxiv.org/repository/view/4827/">deepest waters of Deming Lake never reach the surface</a>. This prevents oxygen in its top layer of water from ever mixing into its deep layer.</p>
<p>Less than 1% of lakes are meromictic, and most that are have dense, salty bottom waters. Deming Lake’s deep waters are not very salty, but of the salts in its bottom waters, <a href="https://doi.org/10.1016/j.earscirev.2020.103430">iron is one of the most abundant</a>. This makes Deming Lake one of the rarest <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/meromictic-lake">types of meromictic lakes</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="man seated in small boat wearing gloves injecting water into a collection tube" src="https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554302/original/file-20231017-23-utrjoi.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Postdoc researcher Sajjad Akam collects a water sample for chemical analysis back in the lab.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The lake surface is calm, and the still air is glorious on this cool, cloudless August morning. We lower a 2-foot-long water pump zip-tied to a cable attached to four sensors. The sensors measure the temperature, amount of oxygen, pH and amount of chlorophyll in the water at each layer we encounter. We pump water from the most intriguing layers up to the boat and fill a myriad of bottles and tubes, each destined for a different chemical or biological analysis.</p>
<p>My colleagues and I have homed in on Deming Lake to explore questions about how microbial life adapted to and changed the environmental conditions on early Earth. Our planet was inhabited <a href="https://theconversation.com/were-viruses-around-on-earth-before-living-cells-emerged-a-microbiologist-explains-197880">only by microbes</a> for most of its history. The atmosphere and the oceans’ depths didn’t have much oxygen, but they did have a lot of iron, just like Deming Lake does. By investigating what Deming Lake’s microbes are doing, we can better understand how billions of years ago they helped to transform the Earth’s atmosphere and oceans into what they’re like now.</p>
<h2>Layer by layer, into the lake</h2>
<p>Two and a half billion years ago, ocean waters had enough iron to form today’s globally distributed <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/banded-iron-formation">rusty iron deposits called</a> <a href="https://www.amnh.org/exhibitions/permanent/planet-earth/how-has-the-earth-evolved/banded-iron-formation">banded iron formations</a> that supply iron for the modern global steel industry. Nowadays, oceans have only <a href="https://youtu.be/EpzEv0H4lvg">trace amounts of iron</a> but abundant oxygen. In most waters, iron and oxygen are antithetical. Rapid <a href="https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Boundless)/05%3A_Microbial_Metabolism/5.10%3A_Chemolithotrophy/5.10D%3A__Iron_Oxidation">chemical and biological reactions between iron and oxygen</a> mean you can’t have much of one while the other is present.</p>
<p>The rise of oxygen in the early atmosphere and ocean was due to <a href="https://ucmp.berkeley.edu/bacteria/cyanointro.html">cyanobacteria</a>. These single-celled organisms <a href="https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change">emerged at least 2.5 billion years ago</a>. But it took roughly 2 billion years for the oxygen they produce via photosynthesis to build up to <a href="https://askanearthspacescientist.asu.edu/oxygen-animal-evolution">levels that allowed for the first animals</a> to appear on Earth.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="water concentrated on a filter looks pale green" src="https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chlorophyll colors water from the lake slightly green.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>At Deming Lake, my colleagues and I pay special attention to the water layer where the chlorophyll readings jump. <a href="https://www.britannica.com/science/chlorophyll">Chlorophyll is the pigment</a> that makes plants green. It harnesses sunlight energy to turn water and carbon dioxide into oxygen and sugars. Nearly 20 feet (6 meters) below Deming’s surface, the chlorophyll is in cyanobacteria and photosynthetic algae, not plants. </p>
<p>But the curious thing about this layer is that we don’t detect oxygen, despite the abundance of these oxygen-producing organisms. This is the depth where iron concentrations start to climb to the high levels present at the lake’s bottom.</p>
<p>This high-chlorophyll, high-iron and low-oxygen layer is of special interest to us because it might help us understand where cyanobacteria lived in the ancient ocean, how well they were growing and how much oxygen they produced. </p>
<p>We suspect the reason cyanobacteria gather at this depth in Deming Lake is that there is more iron there than at the top of the lake. Just like <a href="https://theconversation.com/blood-in-your-veins-is-not-blue-heres-why-its-always-red-97064">humans need iron for red blood cells</a>, cyanobacteria need lots of iron to help catalyze the reactions of photosynthesis.</p>
<p>A likely reason we can’t measure any oxygen in this layer is that in addition to cyanobacteria, there are a lot of other bacteria here. After a good long life of a few days, the cyanobacteria die, and the other bacteria feed on their remains. These bacteria rapidly use up any oxygen produced by still photosynthesizing cyanobacteria the way a fire does as it burns through wood.</p>
<p>We know there are lots of bacteria here based on how cloudy the water is, and we see them when we inspect a drop of this water under a microscope. But we need another way to measure photosynthesis besides measuring oxygen levels. </p>
<h2>Long-running lakeside laboratory</h2>
<p>The other important function of photosynthesis is converting carbon dioxide into sugars, which eventually are used to make more cells. We need a way to track whether new sugars are being made, and if they are, whether it’s by photosynthetic cyanobacteria. So we fill glass bottles with samples of water from this lake layer and seal them tight with rubber stoppers.</p>
<p>We drive the 3 miles back to the <a href="https://cbs.umn.edu/itasca">Itasca Biological Station and Laboratories</a> where we will set up our experiments. The station opened in 1909 and is home base for us this week, providing comfy cabins, warm meals and this laboratory space.</p>
<p>In the lab, we inject our glass bottle with carbon dioxide that carries an <a href="https://www.britannica.com/science/isotopic-tracer">isotopic tracer</a>. If cyanobacteria grow, their cells will incorporate this isotopic marker. </p>
<p>We had a little help to formulate our questions and experiments. University of Minnesota students attending summer field courses collected decades worth of data in Itasca State Park. A diligent university librarian digitized <a href="https://cbs.umn.edu/itasca/research/student-research-papers">thousands of those students’ final papers</a>.</p>
<p>My students and I pored over the papers concerning Deming Lake, many of which tried to determine whether the cyanobacteria in the chlorophyll-rich layer are doing photosynthesis. While most indicated yes, those students were measuring only oxygen and got ambiguous results. Our use of the isotopic tracer is trickier to implement but will give clearer results.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman holds a clear plastic bag aloft, she and man are seated in boat" src="https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Graduate students Michelle Chamberlain and Zackry Stevenson about to sink the bottles for incubation in Deming Lake.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>That afternoon, we’re back on the lake. We toss an anchor; attached to its rope is a clear plastic bag holding the sealed bottles of lake water now amended with the isotopic tracer. They’ll spend the night in the chlorophyll-rich layer, and we’ll retrieve them after 24 hours. Any longer than that and the isotopic label might end up in the bacteria that eat the dying cyanobacteria instead of the cyanobacteria themselves. We tie off the rope to a floating buoy and head back to the station’s dining hall for our evening meal.</p>
<h2>Iron, chlorophyll, oxygen</h2>
<p>The next morning, as we wait for the bottles to finish their incubation, we collect water from the different layers of the lake and add some chemicals that kill the cells but preserve their bodies. We’ll look at these samples under the microscope to figure out how many cyanobacteria are in the water, and we’ll measure how much iron is inside the cyanobacteria. </p>
<p>That’s easier said than done, because we have to first separate all the “needles” (cyanobacteria) from the “hay” (other cells) and then clean any iron off the outside of the cyanobacteria. Back at Iowa State University, we’ll shoot the individual cells one by one into a flame that incinerates them, which liberates all the iron they contain so we can measure it.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="rowboat with one woman in it on a lake with woodsy shoreline" src="https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Biogeochemist Katy Sparrow rows a research vessel to shore.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our scientific hunch, or <a href="https://www.britannica.com/science/scientific-hypothesis">hypothesis</a>, is that the cyanobacteria that live in the chlorophyll- and iron-rich layer will contain more iron than cyanobacteria that live in the top lake layer. If they do, it will help us establish that greater access to iron is a motive for living in that deeper and dimmer layer.</p>
<p>These experiments won’t tell the whole story of why it took so long for Earth to build up oxygen, but they will help us to understand a piece of it – where oxygen might have been produced and why, and what happened to oxygen in that environment.</p>
<p>Deming Lake is quickly becoming its own attraction for those with a curiosity about what goes on beneath its tranquil surface – and what that might be able to tell us about how new forms of life took hold long ago on Earth.</p><img src="https://counter.theconversation.com/content/210997/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizabeth Swanner receives funding from the U.S. National Science Foundation and the National Aeronautics and Space Administration. </span></em></p>An unusual lake with distinct layers of low-oxygen and high-iron water lets researchers investigate conditions like those in the early Earth’s oceans.Elizabeth Swanner, Associate Professor of Geology, Iowa State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2009752023-03-14T12:24:27Z2023-03-14T12:24:27ZClimate change threatens spring wildflowers by speeding up the time when trees leaf out above them<figure><img src="https://images.theconversation.com/files/514776/original/file-20230311-17-7x9lo1.jpg?ixlib=rb-1.1.0&rect=23%2C0%2C3970%2C2952&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Native wildflowers, such as these Dutchman’s breeches (_Dicentra cucullaria_) that bloom early in spring are losing access to sunlight as trees leaf out earlier.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/26pTuFq">Katja Schulz/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>For <a href="https://nativeplantherald.prairienursery.com/2020/04/spring-ephemerals-in-the-woodland/">short-lived spring wildflowers</a> such as <a href="https://www.wildflower.org/plants/result.php?id_plant=anqu">wood anemone (<em>Anemone quinquefolia</em>)</a> and <a href="https://www.wildflower.org/plants/result.php?id_plant=dicu">Dutchman’s breeches (<em>Dicentra cucullaria</em>)</a>, timing is everything. These fleeting plants, known as ephemerals, grow in temperate forests around the world, leafing out and flowering early in spring before the trees towering above them leaf out. Emerge too early, and it will still be winter; emerge too late, and it will be too shady under the forest canopy for essential photosynthesis to happen. </p>
<p>Over their evolutionary history, these plants have figured out the best timing for their survival. But climate change is altering spring growing conditions, and plant life is changing along with it. </p>
<p>There are many examples of plants shifting flowering time in response to warming temperatures, such as <a href="http://dx.doi.org/10.1088/1748-9326/ac6bb4">cherry blossoms opening earlier and earlier</a> each year. However, when one part of an ecosystem shifts, will all the organisms that depend on it successfully shift too? Or will they be out of luck? And what if interconnected species respond to change at different rates, leading to disruptions in long-standing ecological relationships?</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/vg0dAcZo3Fw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Participants in the federally funded USA National Phenology Network collect, store and share data on the timing of life cycle events in plants and animals and how climate change is altering those cycles.</span></figcaption>
</figure>
<p>Researchers have been asking these types of questions about phenology – the timing of biological events – <a href="https://press.uchicago.edu/ucp/books/book/chicago/W/bo8829988.html">related to climate change</a> for years. But most studies have focused on plant-animal interactions, like pollinators coming out at the <a href="https://doi.org/10.1042/ETLS20190139">wrong time for flowers</a>. Far fewer have analyzed plant-plant interactions, such as spring ephemerals that need time to grow before trees leaf out above them and block the sunlight.</p>
<p><a href="https://www.rprimacklab.com/">Our research group</a> has investigated the mismatch between understory wildflowers and canopy trees around Concord, Massachusetts, using historical observations recorded by Henry David Thoreau, the author of “<a href="https://www.gutenberg.org/files/205/205-h/205-h.htm">Walden,” his classic account of life in the woods</a>. We found that trees in Concord were more sensitive to spring temperatures than wildflowers were, and that this resulted in earlier tree leaf-out that <a href="https://doi.org/10.1111/ele.13224">reduced available light in the understory</a>. </p>
<p>This finding was an important first step, but we wanted to know whether these patterns persisted in other temperate forests in North America and across the Northern Hemisphere. Our 2023 study shows that <a href="https://doi.org/10.1111/1365-2745.14021">the answer is yes</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A plant with small purple flowers on the forest floor." src="https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=509&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=509&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=509&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=640&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=640&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514778/original/file-20230311-16-lzomuu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=640&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Round-lobed hepatica (<em>Hepatica americana</em>) is an early-blooming wildflower with blue, white or pink flowers, most often found in shaded woodlands.</span>
<span class="attribution"><a class="source" href="https://plants.ces.ncsu.edu/plants/hepatica-americana/">Frtiz Flohr Reynolds/NC State Extension</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>North American mismatches</h2>
<p>For this research we used specimens from herbariums – collections of plants that have been pressed, dried and cataloged. The plants we examined were collected across eastern North America over the past 100 years. We evaluated over 3,000 pressed plant specimens to chart leafing-out time for trees and flowering time for spring wildflowers. </p>
<p>The vast scale of this study was made possible because herbaria have digitized millions of photographs of plant specimens and <a href="https://naturalhistory.si.edu/research/botany/news-and-highlights/digitized">made them available online</a> over the past decade. Before this resource existed, researchers had to travel to many museums scattered around the country. </p>
<figure>
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<figcaption><span class="caption">The herbarium at the Royal Botanic Gardens in Kew, England, is one of the world’s largest and supports genetic research on plants from around the globe.</span></figcaption>
</figure>
<p>Historical weather records are <a href="https://prism.oregonstate.edu">also available online now</a>. This allows researchers to determine spring temperatures for the year and place where each specimen was collected.</p>
<p>Our study enabled us to confirm the results of our work in Concord. We found that as temperatures warm, deciduous trees across eastern north America are advancing their leaf-out timing faster than native wildflowers are responding.</p>
<p>For example, during cooler springs with 24-hour average March and April temperatures of 41 degrees Fahrenheit (5 degrees Celsius), trees leafed out 13 days after native wildflowers. This gave the flowers almost two weeks of full sun on the forest floor. However, during warmer springs, with average temperatures of 58 F (15 C), trees leafed out only 10 days after native wildflowers. This gave the wildflowers about 25% less full sunlight time during which to photosynthesize. </p>
<p>As spring temperatures warm even further with climate change, we expect wildflowers will have even shorter periods of full sunlight. This can mean a sizable decrease in the flowers’ energy supply and ability to survive, grow and reproduce.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pink three-lobed wildflower." src="https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514779/original/file-20230311-3323-eiamcv.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">Trilliums, like this <em>Trillium grandiflorum</em>, bloom from February through June across North America depending on their location.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Trillium_grandiflorum#/media/File:Trillium_grandiflorum_pink1.jpg">Eric Hill/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>We also observed that trees and wildflowers in the warmer southern part of their ranges advanced their leaf-out and flowering times faster, respectively, than those in colder northern locations. In these zones, we found greater timing differences between trees and wildflowers. This means the potential for phenological mismatch, where native wildflowers are more likely to be shaded out by trees, is greater in the southeast U.S. than in areas farther north.</p>
<h2>Parallels and differences on other continents</h2>
<p>For a 2022 study, we collaborated with colleagues from China and Germany to evaluate over 5,000 tree and wildflower specimens collected over the past 120 years. We wanted to see to whether the phenological mismatches that we documented in North America could also be found in temperate forests of <a href="https://doi.org/10.1038/s41467-022-34936-9">East Asia and central Europe</a>. </p>
<p>Our team found a common pattern across all three continents. Trees and wildflowers are active earlier now than in the past, and they are active earlier in warm years and places. </p>
<p>However, in a surprising twist, we didn’t see the North American pattern of trees being more sensitive than wildflowers on the other two continents. In Europe, wildflowers and canopy trees seemed to be shifting together over time. In Asia, the understory wildflowers were shifting more than the trees — meaning they might get more light, not less, in a warmer future.</p>
<p>The differences we found among the three regions were due primarily to variation in the sensitivities of the trees to temperature. Trees in eastern North America responded more strongly to temperature shifts, while Asian trees responded less strongly.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1633812385709408256"}"></div></p>
<p>These results suggest that eastern North American trees have become especially sensitive to temperature as a way of adapting to this region’s <a href="https://earthathome.org/hoe/ne/climate/#">highly variable climate</a>. In contrast, trees in East Asia are apparently more sensitive to other environmental cues, such as day length, when it comes to the timing of spring growth.</p>
<h2>Informing forest management</h2>
<p>Our results pose questions for further research. If spring temperatures aren’t the primary cues determining leaf-out and flowering times of trees and wildflowers in East Asia, what are those cues? How does the declining spring light window for wildflowers in eastern North America affect their energy budgets and ability to survive, grow and flower?</p>
<p>Another question is whether there are any practical management techniques, such as thinning overstory trees or removing invasive plants, that can help wildflowers deal with the ongoing challenges of climate change. Such strategies could help people appreciate and conserve the full range of plants in the forests we depend on and cherish around the world.</p><img src="https://counter.theconversation.com/content/200975/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard B. Primack receives funding from the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Benjamin R. Lee receives funding from the National Science Foundation and Morton Arboretum</span></em></p><p class="fine-print"><em><span>Tara K. Miller received funding from the National Science Foundation. </span></em></p>Many beloved wildflowers bloom in early spring, while trees are still bare and the flowers have access to sunlight. Climate change is throwing trees and wildflowers out of sync.Richard B. Primack, Professor of Biology, Boston UniversityBenjamin R. Lee, Postdoctoral Fellow in Biology, University of PittsburghTara K. Miller, Policy Research Specialist, Repair Lab, University of VirginiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1991772023-02-06T19:02:32Z2023-02-06T19:02:32ZBacteria use life’s original energy source to thrive in the ocean’s lightless depths<figure><img src="https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sunset over New Zealand from the ocean sampling voyage</span> <span class="attribution"><span class="source">Guy Shelley/Monash University</span>, <span class="license">Author provided</span></span></figcaption></figure><p>There are more than <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC33863/">a billion bacteria in just one litre of seawater</a>. How do all of these organisms find the energy and nutrients they need to survive? </p>
<p>In the nutrient-rich waters near the surface of the ocean, the primary energy source is sunlight, which drives photosynthesis, the transformation of light energy into chemical energy. In much of the open ocean, however, a lack of nutrients limits photosynthesis, and in the deep ocean it ceases altogether as there is no sunlight.</p>
<p>Despite this, microbes have found a way to live throughout the vast and dark ocean. How do they do it?</p>
<p>As we <a href="https://doi.org/10.1038/s41564-023-01322-0">report in Nature Microbiology</a>, many ocean bacteria in fact gain energy from two dissolved gases, hydrogen and carbon monoxide, in a process called chemosynthesis. This hidden but ancient process helps maintain the diversity and productivity of our oceans. </p>
<h2>When the lights go out, chemosynthesis prevails</h2>
<p>We aimed to identify the preferred energy sources of microbes in the world’s oceans. </p>
<p>Humans and other animals depend on eating organic foods, while plants rely on photosynthesis. In contrast, microbes use a myriad of energy sources: solar, organic, and inorganic. </p>
<p>Many eat high-energy gases such as hydrogen and even carbon monoxide, which is poisonous to us. They do so by using special enzymes called hydrogenases and carbon monoxide dehydrogenases. </p>
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Read more:
<a href="https://theconversation.com/antarctic-bacteria-live-on-air-and-make-their-own-water-using-hydrogen-as-fuel-171808">Antarctic bacteria live on air and make their own water using hydrogen as fuel</a>
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<p>The world’s oceans contain quite a lot of dissolved hydrogen and carbon monoxide due to various biological and geological processes. Given this, we predicted these gases would be key energy sources for oceanic microbes. </p>
<figure class="align-center ">
<img alt="A white boat with 'Polaris II' and 'University of Otago' on the side travels across the ocean" src="https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508183/original/file-20230205-23-vxufd1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Ocean samples were collected on the University of Otago’s Polaris II research vessel.</span>
<span class="attribution"><span class="source">Benchill/Wikimedia Commons</span></span>
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</figure>
<p>During our five-year study, we surveyed the capabilities and activities of the microbes present in the world’s oceans. We sampled seawater from diverse sites, spanning tropical islands to subantarctic waters. Public data from the global <a href="https://fondationtaraocean.org/en/expedition/tara-oceans/">Tara Oceans study</a> were also analysed. </p>
<p>Using a technique called metagenomic sequencing, we discovered the genetic blueprints of all the microbes in our ocean samples. We also took chemical measurements during the expeditions, analysed bacterial cultures, and used mathematical modelling to understand how the bacteria were getting their energy.</p>
<p>In all the samples we analysed, microbes were using enzymes to gain energy from hydrogen and carbon monoxide. As we expected, photosynthesis was the main source of energy in coastal surface waters – but gas-eating microbes grew more common further away from shore and in the deeper ocean. </p>
<p>In nutrient-poor waters, chemosynthesis may be the main strategy for obtaining energy. </p>
<figure class="align-right ">
<img alt="Two men collect oceanic water samples for microbial analysis." src="https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=803&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=803&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=803&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1010&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1010&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508228/original/file-20230206-27-3mhiv6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1010&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Collecting water samples during an oceanic voyage.</span>
<span class="attribution"><span class="source">Guy Shelley/Monash University</span>, <span class="license">Author provided</span></span>
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</figure>
<p>Eight distantly related groups, or phyla, of bacteria made the enzymes to use hydrogen and carbon monoxide. Clearly chemosynthesis is a far more widespread strategy in the oceans than previously thought!</p>
<p>Hydrogen and carbon monoxide aren’t the only chemical energy sources supporting ocean bacteria. Building on previous work by others, we found <a href="https://www.nature.com/articles/ismej201618">ammonia</a>, <a href="https://www.frontiersin.org/articles/10.3389/fmicb.2019.00849/full">sulfide</a> and <a href="https://journals.asm.org/doi/10.1128/AEM.66.8.3125-3133.2000">thiosulfate</a> were also widely used. </p>
<p>Together, all these inorganic energy sources allow diverse microbes to prosper even in the darkest and most nutrient-poor regions of the ocean. As we have <a href="https://theconversation.com/in-the-dark-freezing-ocean-under-antarcticas-largest-ice-shelf-we-discovered-a-thriving-microbial-jungle-175735">previously reported</a>, chemosynthesis even allows a “microbial jungle” to form beneath the ice sheets of Antarctica.</p>
<h2>An ancient trait that remains surprisingly widespread today</h2>
<p>Chemosynthesis is less well known than photosynthesis, but it has much more ancient roots. <a href="https://www.nature.com/articles/nrmicro1991">Leading theories on the origin of life</a> suggest hydrogen – produced in hydrothermal vents devoid of sunlight – was the first energy source for life. Photosynthesis likely evolved much later, providing the oxygen in the atmosphere that supports human life. </p>
<p>Some ecosystems still exist today that are primarily driven by chemosynthesis, most notably “<a href="https://en.wikipedia.org/wiki/Hydrothermal_vent#Black_smokers_and_white_smokers">black smokers</a>”. Here, inorganic energy sources released from underwater volcanoes support complex microbially driven ecosystems, which include giant tube worms (you might have seen these on David Attenborough’s <a href="https://www.youtube.com/watch?v=-GrzErwfc8o">Blue Planet</a>). But it’s conventionally thought that most ecosystems today are either directly or indirectly driven by photosynthesis.</p>
<p>Our findings suggest the situation is more complicated. By presenting the first report of hydrogen consumption in open oceans, we reveal unexpected similarities of marine microorganisms today to their ancient ancestors. </p>
<p>Chemosynthesis remains highly active today and provides a lifeline for oceanic microbes when photosynthesis is low. </p>
<p>The hydrogenases that modern marine bacteria use to consume hydrogen appear to be directly descended from the ancient catalysts that supported the first life. But through billions of years of evolution, they’ve adapted to the lower hydrogen and higher oxygen levels of today. </p>
<figure class="align-center ">
<img alt="The sun sets over the ocean, viewed from a boat at sea" src="https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508184/original/file-20230205-13-bdi31h.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Sunset over New Zealand during an ocean sampling voyage.</span>
<span class="attribution"><span class="source">Guy Shelley/Monash University</span>, <span class="license">Author provided</span></span>
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</figure>
<p>Interestingly, hydrogen and carbon monoxide appear to have distinct roles for ocean bacteria. </p>
<p>Hydrogen-consuming microbes grow using the slow, steady feed of energy provided by this gas. These bacteria are often ultrasmall and adapted to life with minimal energy, as reflected by our experiments with the polar bacterium <em>Sphingopyxis alaskensis</em>.</p>
<p>In contrast, carbon monoxide is primarily a “last resort” energy source for bacteria lacking light or organic carbon. It provides enough energy to survive until a better meal, but doesn’t allow for much growth. This agrees with previous work showing <a href="https://www.nature.com/articles/s41396-019-0479-8">carbon monoxide dehydrogenase supports survival</a>, but not growth, of various bacteria.</p>
<h2>Bacterial survival in a changing world</h2>
<p>Through our studies of the oceans and many other environments, it’s now clear that chemosynthesis is a universal process and microbes are actually quite flexible in their diets. Such insights improve our understanding of how ocean microbes survive, produce and consume nutrients, and adapt to their environment. </p>
<p>In turn, we are better able to predict how they may respond to a changing climate and other pressures. The deep ocean, often considered Earth’s “final frontier”, no doubt holds many other secrets big and small.</p>
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Read more:
<a href="https://theconversation.com/they-say-we-know-more-about-the-moon-than-about-the-deep-sea-theyre-wrong-197410">They say we know more about the Moon than about the deep sea. They're wrong</a>
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<img src="https://counter.theconversation.com/content/199177/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Greening receives funding from the Australian Research Council, National Health & Medical Research Council, Human Frontiers Science Program, Australian Antarctic Division, and Monash University.</span></em></p><p class="fine-print"><em><span>Rachael Lappan receives funding from the Australian Research Council and Monash University.</span></em></p><p class="fine-print"><em><span>Zahra F. Islam receives funding from the Australian Academy of Sciences and the University of Melbourne. </span></em></p>In the deep, dark ocean, sunlight-deprived bacteria turn to different sources of energy: dissolved hydrogen and carbon monoxide.Chris Greening, Professor, Microbiology, Monash UniversityRachael Lappan, Group Leader and ARC DECRA Fellow, Monash UniversityZahra F. Islam, Postdoctoral research fellow, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1891452022-09-26T13:28:59Z2022-09-26T13:28:59ZSome plants can short-circuit the toxic effects of metals – now scientists are trying to harness their power<figure><img src="https://images.theconversation.com/files/480324/original/file-20220822-3952-nba0xr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Heavy metals can be toxic to plants - and humans, too.</span> <span class="attribution"><span class="source">Andrii Yalanskyi/Shutterstock</span></span></figcaption></figure><iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/some-plants-can-short-circuit-the-toxic-effects-of-metals-now-scientists-are-trying-to-harness-their-power-189145&bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<p>At first glance, it’s hard to see what gold, iron, lead, arsenic, silver, platinum and tin have in common. A look at the <a href="https://pubchem.ncbi.nlm.nih.gov/periodic-table/">periodic table</a> will clear up the confusion: they are all heavy metals, typically categorised as those metals with an atomic weight and density at least five times greater than water. </p>
<p>These and other heavy metals occur naturally in the environment, and in some cases, in our bodies. They’re mostly considered harmless but at certain levels of exposure they can be toxic to human, plant and animal life. Being over exposed to heavy metals can stunt plants’ growth and lower seed production. </p>
<p>Some plants have <a href="https://www.sciencedirect.com/science/article/abs/pii/S0065250408602020">evolved traits</a> that increase their tolerance of heavy metals. Many researchers, myself among them, believe that understanding and harnessing these evolutionary traits may allow us to protect agricultural crops from the bad effects of heavy metal toxicity.</p>
<p>My research focuses on improving the tolerance of plants to heavy metals, which is particularly important in a country like South Africa, where <a href="https://theconversation.com/how-mine-dumps-in-south-africa-affect-the-health-of-communities-living-nearby-77113">mining activities contaminate soils</a>. These soils are critical for agriculture. </p>
<p>Even plants in the same family use different strategies to cope with metals. Some take up the metals in their roots and transfer them to their leaves; others take up the metals and hold them (immobile) in their roots. This is important for food security and food safety since we want plants that can limit metal uptake into their edible parts. However, as my colleagues and I outline in a <a href="https://www.mdpi.com/2223-7747/9/12/1781">recent review paper</a>, it’s no easy task to harness these strategies.</p>
<h2>Exposure and risk</h2>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0254629909003159">Heavy metal stress or toxicity</a> in plants happens when they are exposed to heavy metals in the soil. </p>
<p>That exposure is usually the result of waste and pollutants from human activities like agriculture, mining and industry. In South Africa, mining has been a <a href="https://core.ac.uk/download/pdf/222967782.pdf">leading culprit</a> of heavy metal pollution.</p>
<p>This inhibits plants’ growth or their ability to convert sunlight into essential energy through photosynthesis. Or it may affect how they assimilate nutrients, or how they respond to drought or harmful pathogens.</p>
<p>This has implications for the production of food crops. <a href="https://www.researchgate.net/publication/281995800_Effects_and_risk_assessment_of_heavy_metals_in_sediments_of_Dahuanjiang_River_since_tailing_dam_break">Studies around the world</a> have found that heavy metal toxicity can reduce crop yields as well as their quality. <a href="https://www.sciencedirect.com/science/article/pii/S0254629914000696">Medicinal plants</a> can also be affected by heavy metals.</p>
<h2>How plants do it</h2>
<p>Plants have evolved some mechanisms to fend off heavy metals effects. I <a href="https://scholar.google.com/citations?hl=en&user=udMWloIAAAAJ&view_op=list_works&sortby=pubdate">study</a> one of these: signalling mechanisms that plants use to control the uptake of heavy metals – their “immune” response to heavy metals.</p>
<p>In much the same way as the human immune system is alerted to, monitors and responds to a pathogen, plants have evolved signalling mechanisms that help them to regulate their tolerance to heavy metals.</p>
<p>These signalling mechanisms are impressive. For example, plants can trigger signalling events to <a href="https://link.springer.com/article/10.1007/s11120-020-00768-1">release low-molecular-weight ligands (ions or molecules)</a> that tightly bind to the heavy metals and prevent them from moving from the roots.</p>
<p>But they’re far from perfect. As human viruses like HIV and SARS-CoV-2 (the coronavirus behind COVID-19) <a href="https://www.nih.gov/news-events/nih-research-matters/how-covid-19-variants-evade-immune-response">have shown</a>, certain pathogens can short-circuit the immune system. Heavy metals can do the same to the plant’s signalling mechanisms by mimicking essential nutrients; for instance, the metal <a href="https://pubs.rsc.org/en/content/articlehtml/2015/mt/c4mt00304g">vanadium resembles phosphate</a>. </p>
<p>Heavy metals like copper have also been shown to damage the membrane integrity of the cell walls in the roots of plants. Similarly, heavy metals can disrupt the construction of these cell walls; weakened walls make the cell lose structural integrity, which exposes the cellular membranes and causes cell death. </p>
<p>Heavy metals can also impair the work of the plasma membrane, which regulates the transport of material in and out of the plant cells. This blocks the uptake of essential nutrients by negating the function of numerous transporter proteins at work in the plasma membranes.</p>
<h2>Useful lessons</h2>
<p>Despite their shortcomings, these signalling mechanisms are powerful. That’s why I study them: if we can tap into the way in which plants adapt to the threats from heavy metals, there’s a chance that soil contaminated with heavy metals can be rejuvenated through the use of the right plants, or that this tolerance can be passed on to other plants, including food crops.</p>
<p>Our ongoing work, and that of others, is promising, but it’s still early days. Perhaps one day soon, plants’ clever adaptations will signal a change in how we deal with heavy metal toxicity.</p><img src="https://counter.theconversation.com/content/189145/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marshall Keyster receives funding from the Department of Science and Innovation (DSI) and Technology Innovation Agency (TIA). He is affiliated with the University of the Western Cape. </span></em></p>Plants have evolved several ways to deal with heavy metals that might otherwise poison or kill them.Marshall Keyster, Associate professor, University of the Western CapeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1851712022-08-29T12:40:26Z2022-08-29T12:40:26ZDo humans really need other species?<figure><img src="https://images.theconversation.com/files/476534/original/file-20220728-1306-a2vwxp.jpg?ixlib=rb-1.1.0&rect=30%2C0%2C6679%2C4456&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Science shows that humans are happier and healthier around other animal and plant species.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/hiker-with-yellow-coat-walking-in-the-deep-forest-royalty-free-image/1323397248?adppopup=true">Artur Debat/Moment via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<blockquote>
<p><strong>Can humans live without any other species of plants or animals? – Arunima S., age 14, Chhindwara, Madhya Pradesh, India</strong></p>
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<p>People definitely cannot survive without other species.</p>
<p><a href="https://scholar.google.com/citations?user=0ePGCP8AAAAJ&hl=en&oi=ao">As an ecologist</a> – a scientist who studies the interactions of plants, microorganisms, fungi and animals, including humans – I know there are at least three reasons we need other organisms.</p>
<h2>Humans need other species to produce food</h2>
<p>First, without other species people would have nothing to eat.</p>
<p>Humans and all organisms require food for energy and the materials to build their bodies and reproduce. Only some microorganisms and plants have a way to <a href="https://www.nature.com/scitable/knowledge/library/terrestrial-primary-production-fuel-for-life-17567411/">use energy from sunlight, water and carbon dioxide</a> to make the basic molecules that provide that food. <a href="https://education.nationalgeographic.org/resource/photosynthesis">This process is called photosynthesis</a>. </p>
<p>Without these organisms, humans wouldn’t have food to eat. Almost everything we eat is either a plant or other photosynthetic organism, an animal that grazes on them, or an animal that feeds on animals that graze. </p>
<p>Processed foods may not look like they come from microbes, plants, fungi or animals, but nearly all do. Some vitamins and other food ingredients are manufactured, but they are only a very small component of the human diet. </p>
<p>Chemists have discovered ways to use various sources of energy to <a href="https://doi.org/10.1016/j.jcou.2021.101726">make molecules that could be used for food</a>. Molecules produced this way are called “synthetic.” However, these processes are so difficult and expensive that it is currently impossible to feed people with these synthetic foods. </p>
<p>Production of synthetic food <a href="https://doi.org/10.1016/j.fufo.2021.100025">using genetically modified bacteria or cultured cell lines</a> is growing in importance. In the future, the human diet may become a little less dependent on consuming plants and animals. Still, living organisms will remain a core component of these foods. </p>
<p>It takes countless different organisms – big, small and microscopic – to <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/soils/health/biology/?cid=nrcs142p2_053868">create healthy soil</a> and <a href="https://doi.org/10.1016/j.tplants.2018.03.004">breathable air</a>. To break down and recycle waste. To purify water and prevent erosion. To break down toxic chemicals into harmless forms, and convert other chemicals into sources of nourishment <a href="https://www.youtube.com/watch?v=BCH1Gre3Mg0">that other organisms need to grow and thrive</a>.</p>
<p>And many of our food plants – over 1,200 species – <a href="https://www.pollinator.org/pollinators">depend on pollinators to produce the fruit or seed</a> that humans and other animals eat. Pollination, the process that allows plants to reproduce, happens when animals carry pollen from one plant to another. Bees are the main pollinators, but many other insects, birds, bats and other animals also transport pollen between plants.</p>
<figure class="align-center ">
<img alt="Yellow, brown and green bird perching on a red flower." src="https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476537/original/file-20220728-11927-udlpwj.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">Birds and other animals fertilize plants by transporting pollen between them – enabling them to produce fruits and seeds that humans eat.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/little-spiderhunter-bird-royalty-free-image/858993576?adppopup=true">krisanapong detraphiphat/Moment via Getty Images</a></span>
</figcaption>
</figure>
<p>Animals of all sizes, from tiny ants to enormous elephants, also <a href="https://theconversation.com/with-fewer-animals-to-spread-their-seeds-plants-could-have-trouble-adapting-to-climate-change-174516">move seeds, spreading plants</a> that make for healthy and productive ecosystems. Diverse species, from tiny microbes to huge vultures and sharks, <a href="https://www.pbs.org/video/natureworks-decomposers-and-scavengers/">break down dead organisms</a> into chemicals that can be used to grow more food.</p>
<p>The number of species that contribute to creating each bite of the average meal is mind-boggling.</p>
<h2>Human bodies need other species to stay healthy</h2>
<p>Many functions of the human body itself rely on a complex and highly diverse ecosystem of microbial species that live on the skin and in the respiratory, digestive and reproductive systems. These bacteria, fungi and other microbes are called a “<a href="https://www.youtube.com/watch?v=1X8p0vhsWRE">microbiome</a>.”</p>
<p>Each person has a unique personal microbiome to protect against infection, <a href="https://theconversation.com/the-human-microbiome-is-a-treasure-trove-waiting-to-be-unlocked-118757">digest and extract nutrients in food</a> and synthesize vitamins. </p>
<p>For example, the gut microbiome is important for breaking down food into usable energy and nutrients, and converting other indigestible or toxic substances into forms that can be excreted. </p>
<p>This microbiome changes over people’s lifetimes based on what they eat, what’s around them, where they live and how healthy they are. In fact, human bodies <a href="https://www.sciencealert.com/how-many-bacteria-cells-outnumber-human-cells-microbiome-science">are made up of more bacterial cells than human cells</a>. </p>
<p>Diet and drugs strongly affect the 300 to 500 bacteria species <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3983973/">that are the core of a healthy gut ecosystem</a>.</p>
<p>The microbiome also plays an important role in preventing infection. Many diseases are associated with microbial communities that are <a href="https://doi.org/10.1136/bmj.k2179">dominated by just a few species</a>. Some physicians <a href="https://doi.org/10.3389/fmicb.2021.519836">transplant poop from healthy to ill people</a> to establish a healthy community of microbes and hopefully cure the disease.</p>
<h2>Humans are happier around other species</h2>
<p>Finally, research shows that people are healthier and more content <a href="https://www.youtube.com/watch?v=1GqdShUJNSA">when they are around other species</a> of plants and animals. They need to <a href="https://www.psychologytoday.com/us/basics/biophilia#how-nature-improves-well-being">experience the sights, sounds, smells, feel and taste</a> of other organisms for mental and physical health. This drive is called “biophilia,” meaning love of living things.</p>
<p>For example, seeing and hearing birds creates positive feelings. Two recent studies in Canada and Germany found that <a href="https://www.audubon.org/news/more-birds-bring-more-happiness-according-science">the more species of birds</a> in a neighborhood, <a href="https://doi.org/10.3390/land10020153">the happier people are</a>. This may be due to experiencing the birds themselves, or due to a healthy environment, as indicated by the presence of birds.</p>
<p>In a different Canadian experiment, researchers played birdsong from hidden speakers along hiking trails. People reported that <a href="https://doi.org/10.1098/rspb.2020.1811">they felt more restored and were more satisfied</a> about the hike when they heard a diversity of birds species than when they heard few or none. </p>
<p>Today, <a href="https://news.un.org/en/story/2014/07/472752-more-half-worlds-population-now-living-urban-areas-un-survey-finds">more than half the world’s population lives in cities</a> instead of the countryside. So urban planners and landscape architects are exploring <a href="https://eos.org/features/growing-equity-in-city-green-space">ways to include more green spaces and green infrastructure</a> in cities.</p>
<p>Research shows that when a city has <a href="https://doi.org/10.1007/s40572-021-00321-9">diverse wildlife, ample open green space and vegetation</a> along streets and on buildings, people are more active, less stressed, healthier and happier. These conditions provide opportunities for <a href="https://doi.org/10.1038/s42949-021-00027-9">people to experience and interact with other organisms</a>, as well as benefit from the other things that plants, animals and microbes do to make the environment healthy and pleasant.</p>
<p>Scientists now know that it takes thousands of species to support human life. Yet we are only just beginning to understand the <a href="https://www.nature.com/scitable/knowledge/library/biodiversity-and-ecosystem-stability-17059965/">important roles different species play in ecosystems</a>, including urban ones. We still need to learn much more about why and how other species are necessary for human survival. And if people are to successfully travel for long periods in space or establish space colonies, we will have to understand what species we need to take along with us to survive and prosper. </p>
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<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/185171/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tom Langen does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>People wouldn’t last long without the countless other species we depend on for survival.Tom Langen, Professor of Biology, Clarkson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1880722022-08-08T20:02:57Z2022-08-08T20:02:57Z15 years of experiments have overturned a major assumption about how thirsty plants actually are<figure><img src="https://images.theconversation.com/files/477980/original/file-20220808-90408-rohu21.jpg?ixlib=rb-1.1.0&rect=3%2C683%2C2189%2C1896&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/CfimHDZtG3o">Hasan Almasi / Unsplash</a></span></figcaption></figure><p>Have you ever wondered just how much water plants need to grow, or indeed why they need it? Plants lose a lot of water when they take in carbon dioxide from the atmosphere, so they need up to 300 grams of water to make each gram of dry plant matter.</p>
<p>But it doesn’t have to be that way. In a <a href="https://www.nature.com/articles/s41477-022-01202-1">new paper published in Nature Plants</a>, we report on a natural secret that could ultimately be used to help plants thrive while using less water. </p>
<h2>An essential ingredient for plant growth</h2>
<p>Plants are mostly made up of water – about 80% by weight. So we might expect plants would need around four grams of water for each gram of dry mass to achieve their ideal level of hydration.</p>
<p>That may be so, but they need a lot more water to grow. To produce one gram of new dry mass, a plant needs about 300 grams of water. </p>
<p>Why such a large difference between the amount of water required for hydration and the amount required for growth? Because almost all the water plants take up from the soil through their roots soon rises out into the atmosphere through their leaves. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/i-spent-a-year-squeezing-leaves-to-measure-their-water-content-heres-what-i-learned-187460">I spent a year squeezing leaves to measure their water content. Here's what I learned</a>
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</em>
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<p>Plant leaves are covered in microscopic valves called stomata. Stomata open to let in carbon dioxide from the air, which plants need for photosynthesis and growth. </p>
<p>But when the stomata are open, the moist internal tissue of the leaf is exposed to the drier outside air. This means water vapour can leak out whenever the stomata are open. </p>
<h2>A long-held assumption</h2>
<p>Plant scientists have long assumed the opening and closing of the stomata almost entirely controlled the amount of water evaporating from a leaf. This is because we assumed the air in small pockets inside the leaves was fully saturated with water vapour (another way to say this is that the “relative humidity” is 100%, or very close to it).</p>
<p>If the air inside the leaf is saturated and the air outside is drier, the opening of the stomata controls how much water diffuses out of the leaf. The result is that large quantities of water vapour come out of the leaf for each molecule of carbon dioxide that comes in. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=629&fit=crop&dpr=1 600w, https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=629&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=629&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=791&fit=crop&dpr=1 754w, https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=791&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/477983/original/file-20220808-64533-nw03gm.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=791&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An electron microscope image of a leaf shows fine hairs called trichomes and the tiny stomata (oval-shaped slits) which allow the movement of water vapour and carbon dioxide.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Leaf_epidermis.jpg">Louisa Howard / Dartmouth</a></span>
</figcaption>
</figure>
<p>Why did we assume the air inside the leaves has a relative humidity near 100%? Partly because water moves from more saturated places to less saturated places, so we thought cells inside leaves could not sustain their hydration if exposed directly to air with relative humidity much lower than 100%. </p>
<p>But we also made this assumption because we had no method of directly measuring the relative humidity of the air inside leaves. (A <a href="https://www.pnas.org/doi/10.1073/pnas.2008276118">recently developed “hydrogel nanoreporter”</a> that can be injected into leaves to measure humidity may improve this situation.)</p>
<h2>A secret revealed</h2>
<p>However, in a <a href="https://www.nature.com/articles/s41477-022-01202-1">series of experiments</a> over the past 15 years, we have accumulated evidence that this assumption is not correct. When air outside the leaf was dry, we observed that the relative humidity in the air spaces inside leaves routinely dropped well below 100%, sometimes as low as 80%. </p>
<p>What is most remarkable about these observations is that photosynthesis did not stop or even slow down when the relative humidity inside the leaves declined. This means the rate of water loss from the leaves stayed constant, even as the air outside increased its “evaporative demand” (a measure of the drying capacity or “thirstiness” of air, based on temperature, humidity and other factors).</p>
<p>If the leaves restricted their loss of water only by closing their stomata, we would expect to see photosynthesis slowing down or stopping. So it appears plants can effectively control water loss from their leaves while stomata remain open, allowing carbon dioxide to continue diffusing into the leaf to support photosynthesis. </p>
<h2>Using water wisely</h2>
<p>We think plants are controlling the movement of water using special “water-gating” proteins called aquaporins, which reside in the membranes of cells inside the leaf. </p>
<p>Our next experiments will test whether aquaporins are indeed the mechanism behind the behaviour that we observed. If we can thoroughly understand this mechanism, it may be possible to target its activity, and ultimately provide agriculturalists with plants that use water more efficiently. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/rising-carbon-dioxide-is-making-the-worlds-plants-more-water-wise-79427">Rising carbon dioxide is making the world's plants more water-wise</a>
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</em>
</p>
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<p>Over the coming decades, global warming will make the atmosphere increasingly thirsty for evaporated water. We are pleased to report that nature may yet reveal secrets that can be harnessed to boost plant production with limited water resources. </p>
<hr>
<p><em>The authors would like to acknowledge the contributions to this work of Graham Farquhar, Martin Canny (deceased), Meisha Holloway-Phillips, Diego Marquez and Hilary Stuart-Williams.</em></p><img src="https://counter.theconversation.com/content/188072/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lucas Cernusak receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Chin Wong 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>Plants lose huge amounts of water to catch the carbon dioxide they need for photosynthesis – but a new discovery may make them more efficient.Lucas Cernusak, Associate Professor, Plant Physiology, James Cook UniversityChin Wong, Visiting Fellow, Plant Sciences, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1844412022-06-24T18:02:25Z2022-06-24T18:02:25ZAfrican lakes emit far less greenhouse gases than feared, European research reveals<figure><img src="https://images.theconversation.com/files/470322/original/file-20220622-13-scwsh7.JPG?ixlib=rb-1.1.0&rect=0%2C5%2C3776%2C949&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Katwe Bay in Lake Edward (Uganda)</span> <span class="attribution"><span class="source">Author</span></span></figcaption></figure><p>One of the keys to predicting climate change is the modelling of how greenhouse gas (GHG) emissions from natural ecosystems might evolve. This first requires estimating as accurately as possible the current GHG emissions from these ecosystems, as well as their causes.</p>
<p>The assessment involves a constant process of re-evaluation, with scientists having to adapt to the latest measurement techniques, theoretical frameworks and expanding databases. As computers’ power increases, mathematical models grow more complex, capturing space and time representations in finer detail. This re-evaluation may be all the more important and frequent for the systems that have been the least studied up to now. </p>
<h2>Lake emissions: a missing piece from the carbon puzzle</h2>
<p>Rivers and lakes, which have the potential to release high quantities of carbon (CO2) and methane (CH4) to the atmosphere, undoubtedly form part of that latter category. While the capacity of ocean and terrestrial systems such as forests to sequester human-induced CO2 was recognised in the late 1950s, it would take another 30 years (almost a generation of scientists!) for the role of rivers, natural lakes and dams in the carbon cycle to be acknowledged in the mid-1990s. Methane emissions from continental waters, in particular, were only estimated in the mid-2000s. This is because rivers and lakes cover a modest area - typically less than 1% of the land surface - and were therefore not regarded as important CO2 or CH4 emitters in the past.</p>
<p>Similarly, scientists until now only had measured emissions from North American and Scandinavian boreal lakes. To make up for the missing parts of the carbon puzzle, such values were extrapolated to lakes in the rest of the world – including tropical lakes. But this is about as inelegant a solution as conflating the ecology of Northern Canadian forests to the Amazonian ones. </p>
<h2>Carbon-sucking phytoplankton … and methane-producing microorganisms</h2>
<p>Our new study on 24 African lakes, which is published today in <em><a href="https://doi.org/10.1126/sciadv.abi8716">Science advances</a></em> , is about to fill this gap. A collaboration between the University of Liège and scientists from KULeuven, the NAFIRRI and the TAFIRI, it reveals GHG emissions from African lakes behaved very differently from the boreal lakes sampled thus far.</p>
<p>For starters, the warm and luminous conditions associated with the tropical “endless summer” meant some African lakes were home to vast quantities of phytoplankton. These micro-algae remove CO2 from the water thanks to the process of photosynthesis. </p>
<p>Such observations invalidate our assumption based on boreal lakes that African counterparts emitted CO2. Due to cooler and darker conditions, lakes in North America and Scandinavia grow very little phytoplankton and limit themselves instead to “composting” the vegetation debris from the surrounding forests. </p>
<p>Their African counterparts, in contrast, are CO2 sinks.</p>
<p>But the warm tropical conditions have a downside. Indeed, heat is favorable to <em>archaea</em>, a category of microorganisms resembling bacteria that produces methane.
The latter also happen to particularly enjoy feeding off the phytoplankton that sink to the bottom of tropical lakes. As a result, methane concentrations were shown to be much higher in African than boreal lakes, and what is “gained” in tropical lakes by sequestering CO2 is “lost” by emitting CH4.</p>
<h2>Why do certain African lakes emit more than others?</h2>
<p>CO2 and CH4 content also varied widely between the 24 lakes based on water depth and colour. </p>
<p>The shallowest of the sampled African lakes was home to the highest biomass of phytoplankton, therefore hosting the lowest CO2 and the highest CH4 concentrations. In shallow lakes, surface waters, which receive the sunlight necessary for photosynthesis, are at the same time in direct contact with the bottom sediments. The bottom sediment provide nitrogen and phosphorus nutrients are also needed for plant growth - like fertilizer in the garden, leading to optimal growth conditions.</p>
<p>Some types of phytoplankton, such as the heat-loving cyanobacteria, also boast physiological features that allow them to reach much higher densities than other micro-algae. Furthermore, proximity to sediments also explains the high CH4 concentrations in shallow lakes.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470839/original/file-20220624-22-6y78w9.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">Local fishermen help scientists measure CO2 emissions on Lake George in Uganda.</span>
<span class="attribution"><span class="source">Author</span></span>
</figcaption>
</figure>
<p>Our second factor to determine phytoplankton and biomass growth, water colour, depends on the vegetation cover surrounding the lakes. To help yourself visualise this, recall how the puddles you see on a walk in the forest have a tea-looking, brown colour. This is due to the presence of dissolved substances called humic which absorb light and prevent the development of phytoplankton. </p>
<p>Tropical forests bordering African lakes, with their rich soils, are full of the stuff. Conversely, lakes surrounded by savannah in more arid regions of Africa had less humic substances. Their clearer waters allowed the growth of phytoplankton, and thus in this case sequestrated more CO2. </p>
<h2>25 times less CO2 emissions than previously assumed</h2>
<p>Finally, the study drew from a recent spatial database detailing the surface and depth measurements of 72,500 tropical lakes worldwide. An understanding of the mechanisms underlying the production of CO2 and CH4 by lakes (depth and surrounding vegetation cover) allowed for an “informed” rather than a “blind” statistical extrapolation of the data based on a simple average of all the data.</p>
<p>Prior studies assumed tropical lakes emitted up to 1600 mega tons of CO2 per year, equivalent to 40% of global CO2 emissions linked to deforestation or the cumulated emissions of <a href="http://www.globalcarbonatlas.org/en/CO2-emissions">CO2 from Germany, UK, France and Italy</a>. Our research suggests that tropical lakes in fact emit CO2 at a rate 25 times lower.</p>
<p>In conclusion, our research brings good news: until now it was assumed lakes emitted high volumes of CO2 - notwithstanding the modest surfaces they covered. Such beliefs were based on data from lakes in North America and Scandinavia, however, regions where the climate and vegetation cover are conducive to high lake CO2 emissions. In contrast, GHG emissions from tropical lakes are low and had been largely overestimated until now.</p>
<p>The bad news is that because methane producing archaea love warm conditions, future warming of tropical lakes might lead to an increase of CH4 emissions to the atmosphere. Something to keep under surveillance. </p>
<p><em>This study synthesizes measurements obtained over more than 10 years in 24 African lakes including the largest of the African Rift (Victoria, Tanganyika, Albert, Kivu, Edward), during 17 field expeditions, in the framework of 2 BELSPO projects (EAGLES, HIPE) and 5 FNRS projects (TRANS-CONGO, LAVIGAS, TANGAGAS, KYBALGAS, MAITURIK).</em></p><img src="https://counter.theconversation.com/content/184441/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alberto Borges a reçu des financements de BELSPO et du FNRS. </span></em></p>Thanks to their high concentrations of phytoplankton, African lakes emit less CO2 than their boreal counterparts, with important consequences for climate modelling.Alberto Borges, Research Director FRS-FNRS, Associate Professor at ULiège, Université de LiègeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1829442022-05-12T18:00:17Z2022-05-12T18:00:17ZTrees aren’t a climate change cure-all – 2 new studies on the life and death of trees in a warming world show why<figure><img src="https://images.theconversation.com/files/462847/original/file-20220512-23-ic1vbg.jpg?ixlib=rb-1.1.0&rect=0%2C175%2C5568%2C3525&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When trees burn, all the carbon they have stored goes back into the atmosphere.</span> <span class="attribution"><span class="source">Patrick T. Fallon/AFP via Getty Images</span></span></figcaption></figure><p><em>When people talk about ways to slow climate change, <a href="https://doi.org/10.1073/pnas.1710465114">they often mention trees</a>, and for good reason. Forests take up a <a href="https://doi.org/10.5194/essd-12-3269-2020">large amount</a> of the planet-warming carbon dioxide that people put into the atmosphere when they burn fossil fuels. But will trees keep up that pace as global temperatures rise? With companies <a href="https://www.forest-trends.org/publications/state-of-the-voluntary-carbon-markets-2021/">increasingly investing in forests as offsets</a>, saying it cancels out their continuing greenhouse gas emissions, that’s a multibillion-dollar question.</em></p>
<p><em>The results of two studies published in the journals Science and Ecology Letters on May 12, 2022 – <a href="https://doi.org/10.1126/science.abm4875">one focused on growth</a>, the <a href="https://doi.org/10.1111/ele.14018">other on death</a> – raise new questions about how much the world can rely on forests to store increasing amounts of carbon in a warming future. <a href="https://scholar.google.com/citations?user=Yq_Ql6gAAAAJ&hl=en">Ecologist William Anderegg</a>, who was involved in both studies, explains why.</em></p>
<h2>What does the new research tell us about trees and their ability to store carbon?</h2>
<p>The future of forests is on a knife’s edge, with a tug of war between two very important forces: the benefits trees get from increasing levels of carbon dioxide and the stresses they face from the climate, such as heat, drought, fires, pests and pathogens.</p>
<p>Those climate stresses are increasing a lot faster as the planet warms than scientists had expected. We’re seeing <a href="https://e360.yale.edu/features/the-age-of-megafires-the-world-hits-a-climate-tipping-point">immense wildfires</a> and <a href="https://doi.org/10.1038/s41467-022-29289-2">drought-driven forest die-offs</a> much sooner than anyone had anticipated. When those trees die, that carbon goes back into the atmosphere. We’re also seeing evidence that the benefits trees get from higher levels of carbon dioxide in a warming world <a href="https://doi.org/10.1126/science.abm4875">may be more limited</a> than people realize.</p>
<p>This tells us it’s probably not a great idea to count on forests for a widespread carbon sink through the 21st century, particularly if societies don’t <a href="https://theconversation.com/transformational-change-is-coming-to-how-people-live-on-earth-un-climate-adaptation-report-warns-which-path-will-humanity-choose-177604">reduce their emissions</a>.</p>
<figure class="align-center ">
<img alt="A female forestry technician cuts a fallen tree with a chainsaw in a forest with dead and dying pine trees whose needles have turned brown." src="https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462821/original/file-20220512-18-4ruzsy.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">Droughts have made trees more vulnerable to fires and beetle attacks.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/barbara-culp-a-lead-forestry-technician-with-the-santa-fe-news-photo/1442099?adppopup=true">Phillippe Diederich/Getty Images</a></span>
</figcaption>
</figure>
<p>Trees and forests do all sorts of other amazing things – they clean the air and water, and they provide economic value in terms of timber and tourism and pollination. So, understanding how they will grow matters for many reasons.</p>
<h2>There’s an argument that, with more carbon dioxide in the atmosphere, trees will simply grow more and lock that carbon away. What did your study find?</h2>
<p>Two key things affect tree growth: <a href="https://www.nationalgeographic.org/encyclopedia/photosynthesis">photosynthesis</a>, which is how trees turn sunlight and carbon dioxide into food, and the <a href="https://agrilife.org/treecarekit/introduction-to-tree-care/how-trees-grow/">process of cell division</a> and expansion.</p>
<p>There’s been a long-standing debate about which is the biggest driver of tree growth.</p>
<p>A good metaphor here is a cart with two horses. The cart moving down the road is the tree growing, and there are two horses attached, but we don’t know which is actually doing the work of pulling the cart. One horse is photosynthesis. That makes a lot of intuitive sense – it’s where all the carbon comes from for building cells. But we know there’s another horse – in order to grow more wood, trees have to grow layers of cells, and the cells have to expand and divide. That cell growth process is very sensitive to climate changes and tends to shut down when conditions are dry.</p>
<figure class="align-center ">
<img alt="Map of drought in the U.S. showing the western half of the country under drought conditions" src="https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/462817/original/file-20220512-22-sz5tic.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Large parts of the Western U.S. have faced severe drought conditions for years. About half the contiguous U.S. was in drought in May 2022.</span>
<span class="attribution"><a class="source" href="https://droughtmonitor.unl.edu/data/png/20220510/20220510_usdm.png">Drought Monitor/UNL/NOAA/USDA</a></span>
</figcaption>
</figure>
<p>People assume that photosynthesis is the dominant process almost everywhere. But we found <a href="https://doi.org/10.1126/science.abm4875">stronger evidence</a> that these cellular processes that are sensitive to drought actually do more to drive or limit growth.</p>
<p>We used tree ring data from thousands of trees across the U.S. and Europe and <a href="https://doi.org/10.1126/science.abm4875">measurements of photosynthesis from towers in nearby forests</a> to check whether tree growth and photosynthesis were correlated over time. If they followed the same pattern, increasing or decreasing in the same years, that would have suggested photosynthesis was the horse pulling the cart. Instead, we found no correlation.</p>
<p>That suggests that droughts, rather than the amount of carbon dioxide in the air, may have the biggest impact on how quickly trees grow in the future. We’re already <a href="https://www.drought.gov/research-spotlight-climate-driven-megadrought">seeing more frequent and severe droughts</a> in many regions.</p>
<h2>What did you learn about the risk of tree death in the future?</h2>
<p>In the other study, we found that lowering global greenhouse gas emissions could have a <a href="https://doi.org/10.1111/ele.14018">huge impact for avoiding damage</a> to forests from wildfires, drought and insects.</p>
<p>We used years of satellite observations, climate data and <a href="https://www.fia.fs.fed.us/">a network</a> of about 450,000 tree plots across the U.S. where each tree is monitored for climate stress and survival. With that historical data, we built statistical models of the risk U.S. trees face from wildfires, insects and climate stress, primarily related to drought. Then we looked at what might happen under future climate scenarios, with high carbon emissions, medium emissions and low emissions. You can explore the results on an <a href="https://carbonplan.org/research/forest-risks">interactive map</a>.</p>
<figure>
<iframe frameborder="0" class="juxtapose" width="100%" height="370" src="https://cdn.knightlab.com/libs/juxtapose/latest/embed/index.html?uid=9092e91c-d1ad-11ec-b5bb-6595d9b17862"></iframe>
</figure><figure><figcaption>The images above, from CarbonPlan.org’s interactive maps, show how risks to forests from wildfire (orange), drought (pink) and insects (blue) increase over time in a medium-emissions scenario of the future. Move the slider to see the comparison of 2020 and 2090.</figcaption></figure>
<p>The big picture: As the planet warms, wildfire <a href="https://doi.org/10.1111/ele.14018">risk increases</a> substantially over the current century, especially in the Western U.S. In a scenario with medium emissions, wildfire risk is projected to increase by a factor of four. Drought and insect risks increase by about 50% to 80%. </p>
<h2>What does this mean for the use of carbon offsets?</h2>
<p>Together these studies suggest that the benefits carbon dioxide has for growth won’t be nearly as large as people thought, and the risk of climate stress, particularly wildfire, drought and insects, will be much larger than people anticipate.</p>
<p>That has huge implications for using forests as <a href="https://theconversation.com/why-corporate-climate-pledges-of-net-zero-emissions-should-trigger-a-healthy-dose-of-skepticism-156386">carbon offsets</a>.</p>
<p>So far, carbon offset protocols and markets have not really grappled with this updated scientific understanding of the <a href="https://carbonplan.org/research/forest-offsets">risks that forests face</a> from climate change. This tells us that climate policymakers and offset developers need to be very careful about how they count on forest offsets to deliver benefits.</p>
<p>The more hopeful message is that our actions in the next decade matter enormously. If we can rein in the speed of climate change and take a lower-emissions path, that does a huge amount to lower risk and increase the benefits. This isn’t a “throw up our hands and panic” situation – it is our chance to take steps that make sure resilient and sustainable forests last for the future.</p>
<p>What we do with our own emissions and efforts to slow climate change matters immensely for the future of forests.</p><img src="https://counter.theconversation.com/content/182944/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William R L Anderegg receives funding from the David & Lucille Packard Foundation, the National Science Foundation, and the USDA NIFA program. </span></em></p>More carbon dioxide in the air doesn’t necessarily mean more growth for trees, and the increasing risk of wildfires and drought has major consequences, as an interactive map shows.William R.L. Anderegg, Associate Professor of Ecology, School Of Biological Sciences, University of UtahLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1814972022-04-28T13:25:44Z2022-04-28T13:25:44ZRising atmospheric CO₂ may benefit maize crops: first experiment in African conditions<figure><img src="https://images.theconversation.com/files/458567/original/file-20220419-14-wh3qfk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Most maize production relies on natural rainfall, making it vulnerable to changing rainfall patterns.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Global maize production is worth <a href="https://doi.org/10.1111/nyas.12396">billions</a> of dollars annually and is key to global food security because it’s a <a href="https://doi.org/10.3389/fsufs.2020.617009">staple food</a> for billions of people. Most maize production relies on natural rainfall, making it vulnerable to changing rainfall patterns.</p>
<p>This limitation is <a href="https://www.pnas.org/doi/10.1073/pnas.1718031115">likely to intensify</a> in the future because climate change is predicted to lead to lower rainfall in many regions. This could decrease <a href="https://www.pnas.org/doi/10.1073/pnas.1718031115">yields</a> by 10% by the time global temperatures have increased by 4°C. Droughts are also <a href="https://www.ipcc.ch/report/ar5/wg2/">predicted</a> to become more frequent and severe.</p>
<p>Higher temperatures are also predicted for many parts of the world and will have direct <a href="https://www.nature.com/articles/nclimate1832">effects on maize growth</a> and productivity. <a href="https://www.researchgate.net/profile/Michael-Roberts-33/publication/258807246_The_critical_role_of_extreme_heat_for_maize_production_in_the_United_States/links/55aea08608aed9b7dcdda360/The-critical-role-of-extreme-heat-for-maize-production-in-the-United-States.pdf">Warming will also lead to more evaporation</a>, which means that plants lose more water. </p>
<p>But it is difficult to predict the effects of a changing climate on crop yields. That’s because the effects of rainfall and temperature can interact in complex ways. Rising carbon dioxide (CO₂) in the atmosphere, which is a result of industrialisation, only adds to the uncertainty. However, as our <a href="https://academic.oup.com/aob/article-abstract/129/5/607/6524535?redirectedFrom=fulltext">new research</a> conducted in South Africa shows, it may offset some of the impacts of drying and warming on maize crops in tropical growing regions like those found in much of Africa.</p>
<h2>Why CO₂ matters</h2>
<p>CO₂ is an important resource for photosynthesis and its low availability in the atmosphere has been a major limiting factor to plant growth for millennia. This has led some plant groups, particularly grasses, to <a href="https://link.springer.com/article/10.1007/s004420050311">evolve a photosynthetic pathway</a> that concentrates CO₂ and makes photosynthesis more efficient under low CO₂. </p>
<p>Maize also has this pathway, known as C4 photosynthesis. Under warm and humid conditions, its growth is thus not limited by CO₂ availability and so it gains no direct benefit from increasing atmospheric CO₂. However, elevated CO₂ allows plants to take up enough CO₂ while keeping their leaf pores (stomata) partially closed. This decreases plant water loss and could potentially increase the drought tolerance of maize.</p>
<p>Research has been done in <a href="https://www.sciencedirect.com/science/article/abs/pii/S1161030111001456">Europe</a> and the <a href="https://academic.oup.com/plphys/article/140/2/779/6115032">US</a> to ascertain how elevated CO₂ might indirectly increase the productivity of C4 plants like maize. These studies found that elevated CO₂ generally had a positive effect on maize growth and compensated for water limitation and warming. However, temperatures and water stress are much higher in most of Africa and other tropical regions than in Europe and the US, raising the question of whether elevated CO₂ can help overcome reduced rainfall under these much more challenging conditions.</p>
<p>We set out to <a href="https://academic.oup.com/aob/article-abstract/129/5/607/6524535?redirectedFrom=fulltext">address this knowledge gap</a>. Through a series of experiments conducted in South Africa’s Eastern Cape province, we found that future atmospheric CO₂ concentrations are likely to benefit maize production in tropical growing regions like those found in many parts of Africa. This may extend the future land area available to rainfed maize cultivation by making maize production more water use efficient.</p>
<p>However, while CO₂ can prolong soil water availability and slow down the effect of drought on photosynthesis, it cannot compensate for a lack of rainfall entirely. Rainfall seasonality thus still plays an important role in determining where maize can be grown. With more data from tropical growing regions, our ability to predict this will increase.</p>
<h2>A series of experiments</h2>
<p>Experiments are required to predict the interacting effects of increased drought and increased CO₂ on maize yields; these studies allow scientists to manipulate each of these factors, singly and in combination. While manipulating water is fairly straightforward, experimenting with atmospheric CO₂ requires specialised and costly facilities. It is therefore not surprising that the leading experiments on the effects of temperature, water and CO₂ have been done under temperate conditions in the northern hemisphere, where research resources are concentrated.</p>
<p>In 2018, Rhodes University in South Africa launched Africa’s first large-scale elevated CO₂ plant <a href="https://www.ru.ac.za/ruecf/">research facility</a>. Here, in special open-top chambers, we exposed six different maize cultivars bred for South African climates to drought and watering treatments under ambient and elevated CO₂, and at elevated temperatures.</p>
<p>Plants were grown over the summer season and were either irrigated daily or left to grow with only the little rainfall that fell naturally. The study area has too little summer rainfall to be a viable maize growing region; this allowed us to simulate the effects of drought under hot and dry summer conditions.</p>
<p>To examine the effect of atmospheric CO₂, we compared current conditions of 400 parts per million (ppm) to those <a href="https://www.ipcc.ch/report/ar5/wg2/">predicted</a> to occur towards the end of the 21st century (800 ppm). The air temperature in the open-top chambers was 4-5°C higher than ambient, which is in line with future climate <a href="https://www.ipcc.ch/report/ar5/wg2/">predictions</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=512&fit=crop&dpr=1 600w, https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=512&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=512&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=643&fit=crop&dpr=1 754w, https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=643&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/458566/original/file-20220419-24-4dbirn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=643&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Study co-author Tebadi Burgess (née Bopape) holds maize plants that she grew at either current or future atmospheric CO₂ concentrations with and without drought.</span>
<span class="attribution"><span class="source">Authors supplied</span></span>
</figcaption>
</figure>
<h2>Findings</h2>
<p>Under ambient CO₂ and without watering, plants had very low yields. Irrigated plants at elevated CO₂ had nearly four time higher yields. </p>
<p>Adding elevated CO₂ to unwatered plants resulted in the same growth and yield as irrigation at ambient CO₂. This shows that elevated CO₂ had the same effect on plants as daily irrigation and thus completely compensated for drought. When given additional CO₂, plants needed less water, because they could partially close their leaf pores and avoid water loss.</p>
<p>Irrigated maize yields increased with added CO₂. This suggests that even under irrigation, hot and dry weather can cause water stress and reduce productivity.</p>
<p>This research shows that future atmospheric CO₂ concentrations could help alleviate the effects of warming and drought, even for irrigated production. However, more research is needed to determine the effects of intermediate CO₂ concentrations between 400 and 800 ppm, which will be experienced between now and the end of the century. Data on the effects of other variables, such a soil type and severity of climate, are also needed to calibrate realistic models to forecast future maize production.</p>
<p><em>Tebadi Burgess (nee Bopape), an MSc graduate, co-authored the research on which this article is based.</em></p><img src="https://counter.theconversation.com/content/181497/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brad Ripley receives funding from Applied Centre for Climate & Earth Systems Science (ACCESS), Rhodes Unversity and Grain SA.</span></em></p><p class="fine-print"><em><span>Susanne Vetter receives funding from the Applied Centre for Climate & Earth Systems Science (ACCESS) and Rhodes University.</span></em></p>Rising carbon dioxide in the atmosphere may be a boon for maize crops in tropical growing regions like those found in much of Africa.Brad Ripley, Professor, Department of Botany, Rhodes UniversitySusanne Vetter, Associate Professor, Department of Botany, Rhodes UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1811632022-04-14T05:30:09Z2022-04-14T05:30:09ZMulti-coloured plants are suddenly a home decor ‘must-have’. Here’s how to keep them alive<figure><img src="https://images.theconversation.com/files/457621/original/file-20220412-46278-pqir8z.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5065%2C3785&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>Fads and fashion have always influenced the plants we keep. And so it is with variegated plants, which have become <a href="https://thatplantylife.com/affordable-and-gorgeous-variegated-houseplants/">very popular</a> with indoor plant enthusiasts these days.</p>
<p>Variegated plants possess multiple colours – typically on their leaves, but in some cases on stems, flowers and fruit. Their patterns include stripes, dots, edges and patches. They’re usually green with either white or yellow, but can also feature red, pink, silver and other colours.</p>
<p>Variegated plants can divide opinion. I recall a great aunt telling me many years ago of her great fondness for the variegated Aspidistra elatior growing her garden. But I’ve also heard gardeners and garden designers dismiss variegated foliage because it didn’t fit with their design or colour themes.</p>
<p>Now, it seems indoor variegated plants are considered a “<a href="https://www.apartmenttherapy.com/variegated-plant-care-tips-36878935">must-have</a>” home decor accessory. But before you rush out and buy one, make sure you know how to keep it happy.</p>
<figure class="align-center ">
<img alt="woman puts handful of dirt into plant pot" src="https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&rect=14%2C22%2C4889%2C3235&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.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">Variegated plants come in an array of colours and patterns.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Understanding variegated plants</h2>
<p>Most plant species are entirely green but occasionally a variegated individual arises. Some catch the eye of a dedicated plant collector or nursery worker and become a popular variety.</p>
<p>Plant variegation can occur for several reasons.</p>
<p>In some plants, such as the flowers of tulips, it’s due to a <a href="https://www.britannica.com/story/tulip-mania-how-a-plant-virus-fueled-a-speculative-frenzy">viral infection</a>. The resulting streaks of different colours may be cursed or valued depending on the aesthetic effect.</p>
<p>Others plants, such as those in the genus <a href="https://www.rbgsyd.nsw.gov.au/Stories/2019/Coleus-back-in-the-name-game">coleus</a>, are naturally patterned. Groups of cells produce different colour combinations, causing leaves to grow with attractive markings.</p>
<p>Plant variegations can also arise from genetic mutation.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-leaves-green-86160">Curious Kids: Why are leaves green?</a>
</strong>
</em>
</p>
<hr>
<p>When growing variegated plants, it’s important to understand how the various colours affect the way it functions.</p>
<p>The green part of plants contains chlorophyll, a pigment essential for photosynthesis. (Photosynthesis, of course, is the process by which the leaves convert sunlight into oxygen and carbohydrate that provides energy for plants to grow.) </p>
<p>In variegated plants, white parts of leaves do not contain chlorophyll and so do not photosynthesise. </p>
<p>Yellow parts of leaves can help send energy to the chlorophyll, but can’t perform photosynthesis on their own. The same goes for some red, orange and pink patches of tissue.</p>
<p>But all cells in the leaf – green or not – use the plant’s energy. That means variegated plants are less efficient energy producers than their all-green counterparts, which causes them to grow more slowly.</p>
<p>Some plants have mutated into <a href="https://www.chicagobotanic.org/blog/how_to/science_activity_albino_plants">albinos</a> containing no chlorophyll. These normally die within a few days or weeks of germination.</p>
<figure class="align-center ">
<img alt="two indoor variegated plants in pots" src="https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.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">Yellow parts of leaves do not photosynthesise.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Caring for your plant indoors</h2>
<p>It’s no coincidence many popular indoor plants – such as coleus, philodendrons, monsteras, dracaenas and calatheas – are variegated. Because they’re usually far less vigorous than all-green versions of the species, they won’t be pushing against the ceiling within weeks. </p>
<p>The decorative colour and pattern of a variegated indoor plant is an added bonus.</p>
<p>Variegated plants can take longer than others to reach a size considered appropriate for sale at a nursery, so may be comparatively more expensive. But there are ways to protect your variegated investment.</p>
<p>First, watch out for “reversion”. This can occur when a variegated plant sends up an all-green shoot. The shoot will grow fast compared to the variegated parts and can eventually take over, causing the whole plant to revert to green. </p>
<p>To avoid this, vigilantly remove any green shoots before they get big.</p>
<p>You don’t want variegated plants quickly outgrowing their space, but remember they’re low on chlorophyll and so need good light.</p>
<p>And like any indoor plant, ensure its leaves are kept free of fine dust and you don’t give it too much, or too little, water.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-apartment-dwellers-need-indoor-plants-80196">Why apartment dwellers need indoor plants</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="plants on sun-drenched windowsill" src="https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.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">Indoor variegated plants need good light to make up for the lack of chlorophyll.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Variegated plants in the garden</h2>
<p>The popularity of indoor variegated plants will almost certainly lead to greater use outdoors.</p>
<p>Their slow-growing nature means outdoor variegated plants are usually much less likely to be “weedy” and spread where they’re not wanted. </p>
<p>This can be an advantage if you’ve avoided planting a species because it will take over the garden. The variegated versions of <a href="https://www.plantmark.com.au/pittosporum-eugenioides-variegata">pittosporum</a>, ficus and <a href="https://www.rhs.org.uk/plants/57250/nerium-oleander-variegatum-(v)/details">nerium oleander</a>, for example, are far less intent on global domination than their all-green counterparts.</p>
<p>When planting a variegated plant outdoors, watch that it doesn’t become shaded by other quicker-growing plants. Many variegated plants already struggle to photosynthesise sufficiently. A bit of extra shade can damage or even kill them.</p>
<p>So ensure they get enough light – and every so often give them a hand by trimming back nearby plants.</p>
<figure class="align-center ">
<img alt="green and purple plants in garden" src="https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.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">
<figcaption>
<span class="caption">Ensure variegated plants are not over-shaded.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Growing with flying colours</h2>
<p>Variegated plants are having their moment in the sun. But their interesting biology is always in fashion!</p>
<p>These plants can brighten up your indoor space and provide attractive colour and pattern in the garden.</p>
<p>By learning about how variegated plants function and considering their special requirements, you can enjoy them for years to come.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/trees-get-sunburnt-too-but-there-are-easy-ways-to-protect-them-from-tree-sunscreen-to-hydration-172953">Trees get sunburnt too – but there are easy ways to protect them, from tree 'sunscreen' to hydration</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/181163/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gregory Moore 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>Variegated plants can be more expensive than their all-green counterparts. But there are ways to protect your investment.Gregory Moore, Doctor of Botany, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1798122022-04-13T12:13:16Z2022-04-13T12:13:16ZRedwood trees have two types of leaves, scientists find – a trait that could help them survive in a changing climate<figure><img src="https://images.theconversation.com/files/457498/original/file-20220411-11-h2ic9b.jpg?ixlib=rb-1.1.0&rect=16%2C0%2C5542%2C3709&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Coastal redwoods in Felton, California.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/coastal-redwoods-stand-in-the-henry-cowell-redwoods-state-news-photo/915647562">Carolyn Van Houten/The Washington Post via Getty Images</a></span></figcaption></figure><p>Coast redwoods are amazing trees that scientists have studied for generations. We know they are <a href="https://doi.org/10.1038/nature02417">the tallest living trees</a> and have survived for millennia, <a href="https://academic.oup.com/jof/article-abstract/29/6/939/4719848">resisting fire</a> and <a href="https://nzjforestryscience.springeropen.com/articles/10.1186/s40490-014-0017-4">pests</a>. Because redwoods are long-lived, large and decay-resistant, the forests they dominate store <a href="https://doi.org/10.1016/j.foreco.2016.05.018">more above-ground mass, and thus presumably more carbon</a>, than any other ecosystem on Earth. </p>
<p>Nonetheless, while working on a recently published study, colleagues at the <a href="https://scholar.google.com/citations?user=qeqqJqwAAAAJ">University of California</a>, <a href="https://scholar.google.com/citations?user=S3LivCgAAAAJ&hl=es">Davis</a>, and <a href="https://scholar.google.com/citations?user=5dqacuQAAAAJ&hl=en">Cal Poly</a> <a href="https://kerhoulasforestlab.weebly.com/">Humboldt</a> and <a href="https://scholar.google.com/citations?hl=en&user=Qv4DpXAAAAAJ">I</a> learned a secret that had been sitting right under our noses. </p>
<p>Redwoods, it turns out, have two types of leaves that look different and perform very different tasks. This previously unknown feature helps the trees adapt to both wet and dry conditions – an ability that could be key to their survival in a changing climate.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-swLTsWXPII?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Redwoods can live for more than 2,000 years and grow to more than 350 feet tall.</span></figcaption>
</figure>
<h2>Just enough water</h2>
<p>Wherever trees grow, sooner or later their leaves get wet. For trees in wet environments, this can be a problem if films of water <a href="https://doi.org/10.1111/j.1365-3040.1995.tb00377.x">cover their stomata</a>. These tiny pores allow carbon dioxide to enter leaves so the tree can combine it with water to make plant tissue through <a href="https://www.usda.gov/media/blog/2015/03/17/power-one-tree-very-air-we-breathe">photosynthesis</a>. Many trees that are common to wet forests have leaves with adaptations that <a href="https://doi.org/10.1073/pnas.95.24.14256">prevent these water films from forming</a>. </p>
<p>In contrast, trees growing in dry environments take advantage of brief bouts of leaf wetness to <a href="https://doi.org/10.1111/nph.15307">take up valuable water</a> directly across the surfaces of their leaves, <a href="http://dx.doi.org/10.1111/pce.13439">through special leaf structures</a>, and even <a href="https://doi.org/10.1111/pce.14041">through their stomata</a>. But some trees, including coast redwoods, live in both wet and dry environments with intense seasonal variation. </p>
<p>For broad-leaved trees like the <a href="https://doi.org/10.1104/pp.114.242040">holm oak</a>, which grows in Mediterranean climates with dry summers and rainy winters, this seasonal wetness challenge is relatively easy to overcome. Their stomata are on the sheltered undersides of their leaves, which keeps them clear of water, while the leaves’ top surfaces absorb water. But redwoods are conifers, or cone-bearing trees, with <a href="https://ucanr.edu/sites/forestry/California_forests/http___ucanrorg_sites_forestry_California_forests_Tree_Identification_/Coast_Redwood_Sequoia_sempervirens_198/">thin, flat needlelike</a> leaves, and they need a different way to balance the competing goals of repelling and absorbing water. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Oval-shaped opening on a wavy green surface." src="https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=772&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=772&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457504/original/file-20220411-11-gw6ixl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=772&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A single stoma on a tomato leaf, shown via electron microscope.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Stoma#/media/File:Tomato_leaf_stomate_1-color.jpg">Photohound/Wikipedia</a></span>
</figcaption>
</figure>
<p>We knew we wanted to explore how redwoods met the paradoxical challenge of leaf wetness, how much water redwoods could absorb and which leaf features caused differences in water uptake capacity. What we learned came as a total surprise.</p>
<h2>Big trees with big secrets</h2>
<p>Scientists have long known about redwoods’ <a href="https://doi.org/10.1111/j.1365-3040.2004.01207.x">ability to absorb water through their leaves</a>. But figuring out how much water redwoods can absorb this way, and how the capacity to do so might vary from one type of climate to another, is a real challenge in this species. </p>
<p>First, a big redwood has over 100 million leaves with a <a href="https://doi.org/10.1016/j.foreco.2016.05.018">massive amount of surface area</a> for water absorption. And these leaves <a href="https://doi.org/10.1016/j.foreco.2016.05.018">drastically change structure with height</a>, going from long and flat to short and awllike. So we couldn’t get this right by simply picking leaves at ground level.</p>
<p>To complicate matters further, gravity is always pushing down on the giant column of water rising upward through a redwood’s trunk. As a result, leaves at the top of the tree <a href="https://doi.org/10.1038/nature02417">always have less available water</a> than those lower down. The treetop’s inherent dryness should pull water into the leaf more quickly than into water-rich leaves at the bottom, just as a dry sponge picks up water faster than a damp one. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing historic and current distribution of coast redwoods." src="https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=716&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=716&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=716&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=899&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=899&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457508/original/file-20220411-26-5iu2ea.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=899&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Coast redwoods’ range extends from southern Oregon to California’s Big Sur coast.</span>
<span class="attribution"><a class="source" href="https://www.parks.ca.gov/?page_id=24723">California Department of Parks and Recreation</a></span>
</figcaption>
</figure>
<p>For an accurate picture of how redwoods absorbed water, we needed leaves from trees in wet and dry environments, and from multiple heights on those trees. To get them to their natural gravity-based water levels for analysis, we put our leaf samples in a <a href="https://doi.org/10.1111/pce.13327">fog chamber</a> – in this case, an ice chest hooked up to a room humidifier – and measured weight gain over time to see how much water they could absorb.</p>
<h2>A trail of clues</h2>
<p>As we took apart clusters of redwood shoots to immerse them in fog, we divided each cluster into pieces. Redwood shoot clusters fan out from a woody core and are segmented into individual shoots of multiple ages, each with its own set of leaves. We separated shoots along <a href="https://doi.org/10.1093/treephys/tpu011">the woody central axis</a> from the much more common pliable shoots on the outer edges of each cluster. </p>
<p>It quickly became obvious that shoots from the center axis had leaves that could absorb water three times faster than peripheral leaves. When we looked inside the leaves with a microscope, we understood that they were two completely different types. They don’t look the same on the outside either, but this was so unexpected that we needed to see their internal structure to really convince ourselves. </p>
<p>The axial leaves were packed with water storage cells, but their phloem – tubes in the leaves that export photosynthetic sugars to the tree – appeared to be blocked and useless. If a tree has leaves, the conventional wisdom is that they are there for photosynthesis, but we wondered whether the axial leaves had a different purpose.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two types of redwood shoots" src="https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457500/original/file-20220411-13-ve7ex9.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Redwoods’ broad peripheral leaves, shown at left, make up about 95% of the trees’ leaf area and do all the photosynthesis. Their axial leaves, at right, are adept at absorbing water.</span>
<span class="attribution"><span class="source">Alana Chin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>With some additional measurements, we found that redwoods’ axial leaves are specialized for absorbing water. Differences between the surfaces of axial and peripheral leaves, especially their wax coverage, cause the differences in their water absorption rates.</p>
<p>Unlike the axial leaves, redwoods’ peripheral leaves have waxy surfaces with lots of stomata. This helped to explain how they <a href="https://academic.oup.com/treephys/article/30/10/1260/1658568">photosynthesize year-round</a> regardless of the long wet season in much of their current habitat.</p>
<p>Further analysis showed that the redwoods’ axial leaves account for only about 5% of the trees’ total leaf area, and barely produce enough energy through photosynthesis to maintain themselves. But they contribute up to 30% of the trees’ total water absorption capacity. Together these two types of leaves balance the dueling requirements of photosynthesis and water absorption, allowing redwoods to thrive in both wet and dry habitats. </p>
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<p>Using large-scale <a href="https://www.youtube.com/watch?v=B4JAyIAhgIU&t=89s">tree measurements</a> and <a href="https://doi.org/10.1890/14-1016.1">equations for estimating redwood leaf area</a>, we estimated that these thirsty giants can absorb as much as 105 pounds (48 kilograms) of water in the first hour of a rainfall wetting their leaves. That’s equivalent to 101 pints of beer.</p>
<h2>The significance to redwoods</h2>
<p>Understanding what causes the variation in redwood leaves’ uptake capacity can help us gauge differences in water uptake capabilities among trees and environments, now and in the future. In my opinion, this is the most potentially useful part of our study.</p>
<p>Redwoods vary their two leaf types to suit their local climates. In wet rainforests in the northern part of their range, above Mendocino County, the trees invest in fewer of the axial leaves that are specialized for absorbing water. These leaves are concentrated in the trees’ lower crowns, leaving the photosynthetically <a href="https://doi.org/10.1093/treephys/tpp037">high-performing treetops</a> free to maximize sugar production in the bright sun. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Leaf under a microscope, covered with white dots." src="https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=510&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=510&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=510&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=641&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=641&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457510/original/file-20220411-6515-ece0z9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=641&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Wax on the surface of a redwood leaf. The white dots are water-resistant plugs in the stomata.</span>
<span class="attribution"><span class="source">Marty Reed</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In dry forests on the southern margins of redwoods’ range, trees have more axial leaves in their water-stressed tops. This allows them to take better advantage of briefer leaf-wetting events, but it means they photosynthesize less per leaf area than redwoods in wetter areas. </p>
<p>Redwoods’ ability to shift leaf types to match regional climatic differences may help them adjust to climate change in an <a href="https://theconversation.com/californias-water-supplies-are-in-trouble-as-climate-change-worsens-natural-dry-spells-especially-in-the-sierra-nevada-173142">ever-drier California</a>. That would be good news for conserving these epic trees, and it may be a promising feature to investigate as scientists try to <a href="https://onlinelibrary.wiley.com/doi/epdf/10.1111/tpj.15592">link drought tolerance traits</a> to regional differences among redwood populations.</p><img src="https://counter.theconversation.com/content/179812/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alana Chin received funding from the NSF GRFP</span></em></p>New research shows that coast redwood trees have a surprising adaptation that helps them thrive in both wet and dry environments.Alana Chin, Postdoctoral Fellow in Plant Ecology, Swiss Federal Institute of Technology ZurichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1802052022-03-29T12:36:16Z2022-03-29T12:36:16ZArctic greening won’t save the climate – here’s why<figure><img src="https://images.theconversation.com/files/454793/original/file-20220328-19-rmoej.jpg?ixlib=rb-1.1.0&rect=0%2C22%2C3072%2C2023&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Changes in vegetation and temperature affect wildlife and humans, as well as the climate.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/usfws_alaska/51357490933/">Lisa Hupp/USFWS</a></span></figcaption></figure><p>Satellite images show the Arctic has been getting greener as temperatures in the far northern region rise <a href="https://www.amap.no/documents/doc/arctic-climate-change-update-2021-key-trends-and-impacts.-summary-for-policy-makers/3508">three times faster</a> than the global average.</p>
<p>Some theories suggest that this “Arctic greening” will help counteract climate change. The idea is that since plants take up carbon dioxide as they grow, rising temperatures will mean Arctic vegetation will absorb more carbon dioxide from the atmosphere, ultimately reducing the greenhouse gases that are warming the planet.</p>
<p>But is that really happening?</p>
<p>I am a <a href="https://scholar.google.com/citations?user=Qw1L18EAAAAJ&hl=en">biologist who focuses on the response of ecosystems to climate change including tundra ecosystems</a>. For the past five years, my colleagues, students and I have tracked vegetation changes at remote locations across the Arctic to find out.</p>
<h2>Braving bears to collect evidence on the tundra</h2>
<p>The Arctic tundra is a vast, mostly treeless region stretching across the far northern areas of North America and Eurasia. A few feet below its surface, much of the soil is frozen permafrost, but the top layer blooms with grasses and low shrubs during the short summer months.</p>
<p>Satellite studies over the past decade have tracked changes in the greening of the Arctic by measuring the visible and near-infrared light reflected by vegetation. Healthy green vegetation absorbs visible light but reflects the near-infrared light. Scientists can use that data to estimate plant growth across wide areas. </p>
<p>But satellites don’t measure the plants’ carbon dioxide uptake. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Yi8SFOJffFA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Satellite images of the greening Arctic. NASA Goddard Space Institute.</span></figcaption>
</figure>
<p>Until recently, field studies that might verify how much carbon dioxide Arctic plants were taking up were sparse, preventing scientists from testing the hypothesis that earlier snow melt and its impact on plants helped control carbon dioxide in the atmosphere.</p>
<p>For <a href="https://doi.org/10.1038/s41598-022-07561-1">our study</a>, scientists <a href="https://newscenter.sdsu.edu/sdsu_newscenter/news_story.aspx?sid=78713">braved bear territory</a> and cold summer nights to collect extensive carbon dioxide measurements near plants and soil in 11 Arctic tundra ecosystems, including in Alaska, Canada, Siberia and Greenland. We focused on the most understudied Arctic areas, located over continuous permafrost. </p>
<h2>Earlier growth, but a late-season slowdown</h2>
<p>Arctic plants currently have only about three months in which they can grow and reproduce before the temperatures gets too cold.</p>
<p>When we started this study, we wanted to find out what effect the earlier start to the growing season was having on the overall amount of carbon dioxide taken up by vegetation each summer. The results surprised us: Even though the greening was evident, the overall carbon dioxide uptake either did not significantly increase or had only minor increases. </p>
<p>When we looked closer and compared the changes from week to week, we discovered why. While the earlier snowmelt was stimulating plants’ productivity in June, that productivity began to taper off in July – normally their peak season for photosynthesis. By August, productivity was well below normal.</p>
<p>The Arctic’s dominant shrubs, <a href="https://www.nps.gov/articles/000/sedges-and-grasses-of-the-cook-inlet-coast.htm">sedges</a> and other wetland plants were no longer sequestering more carbon late in the season. It was like waking up earlier in the morning and being ready to go to sleep earlier in the evening.</p>
<figure class="align-center ">
<img alt="A map of North America showing green areas in the far north." src="https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=339&fit=crop&dpr=1 600w, https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=339&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=339&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=426&fit=crop&dpr=1 754w, https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=426&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/454794/original/file-20220328-21-1tkvokt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=426&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Satellite data captured at the summer growth peak from 1984-2012 showed extensive greening in the tundra of western Alaska, northern Canada, Quebec and Labrador. It captures evidence of plants, but not carbon dioxide changes.</span>
<span class="attribution"><a class="source" href="https://landsat.gsfc.nasa.gov/article/nasa-studies-details-of-a-greening-arctic/">NASA’s Goddard Space Flight Center/Cindy Starr</a></span>
</figcaption>
</figure>
<p>We still have many questions, including why plants are responding this way and whether the widely used index for plant growth based on changes in visible and infrared light, <a href="https://www.usgs.gov/landsat-missions/landsat-normalized-difference-vegetation-index">called NDVI</a>, is definitively associated with a higher uptake of carbon dioxide. Some Arctic ecosystems have shown <a href="https://arctic.noaa.gov/Report-Card/Report-Card2019/ArtMID/7916/ArticleID/835/Surface-Air-Temperature">strong correlations</a> between NDVI and carbon dioxide uptake, while <a href="https://doi.org/10.1111/j.1365-2486.2009.02107.x">others have not</a>. We didn’t find evidence that plants were affected by water limitations in the late season.</p>
<p>If tundra ecosystems are not able to continue taking up carbon dioxide later in the season, the expected increase in plants sequestering carbon may not materialize. </p>
<p>And there’s another problem. Normally, plants on the tundra store more carbon through photosynthesis than the tundra releases, making it a vast <a href="https://edu-arctic.eu/news/57-what-is-arctic-tundra-doing-with-carbon-dioxide">carbon sink</a>. The long, cold winters slow plants’ decomposition and lock them in the frozen ground. However, when permafrost holding this and other organic matter thaws, it releases more greenhouse gases into the atmosphere.</p>
<figure class="align-center ">
<img alt="Illustration of plant growth by month for early and later snowmelt shows the growing period shift from July-August to June-July." src="https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/454811/original/file-20220328-13-tpii5c.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This infographic illustrates the differences in plant growth each month. When snow melts earlier in the season, plants begin decomposing earlier.</span>
<span class="attribution"><span class="source">Donatella Zona</span></span>
</figcaption>
</figure>
<h2>The local impact goes beyond carbon</h2>
<p>This isn’t just a story about plants and the climate. Vegetation changes can have wide-ranging effects on other components of ecosystems, including animals and people.</p>
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<p>The Intergovernmental Panel on Climate Change, the United Nations body for assessing the science related to climate change, has estimated that changes in snow cover have already <a href="https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/">affected food and water security</a>. Many local native communities depend on hunting, trapping and fishing, and earlier vegetation development can affect the delicate balance of complex Arctic systems.</p>
<p>If Arctic greening is only shifting seasons and isn’t increasing the overall carbon dioxide level as previously believed, that could also mean the models currently used to evaluate and predict the overall impact of climate change are missing an important piece of information. The result could be that a process we assumed would slow or mitigate climate change isn’t actually working as expected.</p><img src="https://counter.theconversation.com/content/180205/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Donatella Zona receives funding from the National Science Foundation (NSF) Office of Polar Programs, from the National Aeronautics and Space Administration (NASA), from the European Union’s Horizon 2020 research and innovation program, from the Natural Environment Research Council (NERC), and from the NOAA Cooperative Science Center for Earth System Sciences and Remote Sensing Technologies (NOAA-CESSRST) </span></em></p>The growing season on the tundra is starting earlier as the planet warms, but the plants aren’t sequestering more carbon, a new study finds.Donatella Zona, Associate Professor of Biology, San Diego State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1769792022-02-17T23:03:03Z2022-02-17T23:03:03ZIn heatwave conditions, Tasmania’s tall eucalypt forests no longer absorb carbon<figure><img src="https://images.theconversation.com/files/446947/original/file-20220217-27-1jhm47y.JPG?ixlib=rb-1.1.0&rect=4%2C0%2C2727%2C1822&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>Southern Tasmania’s tall eucalyptus forests are exceptionally good at taking carbon dioxide from the atmosphere and converting it into wood. </p>
<p>For many years, we have believed these forests had a reasonable buffer of safety from climate change, due to the cool, moist environment. </p>
<p>Unfortunately, my <a href="https://www.nature.com/articles/s41598-022-06674-x">research published today</a> shows these forests are closer to the edge than we had hoped. I found during heatwaves, these forests switch from taking in carbon to pumping it back out. </p>
<p>That’s not good news, given heatwaves are only expected to increase as the world heats up. While we work to slash emissions, we need to explore ways to make these vital forests more resilient. </p>
<h2>From carbon dioxide in to carbon out</h2>
<p>It’s well established from <a href="https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/geb.12171">forest sampling</a> that moist, cool environments like southern Tasmania provide ideal growing conditions for tall eucalypt forests. </p>
<p>We had believed these types of forests would <a href="https://www.science.org.au/supporting-science/science-policy-and-analysis/reports-and-publications/risks-australia-three-degrees-c-warmer-world">have a buffer</a> against the worst effects of climate change to come, and perhaps even benefit from limited warming. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="large gum tree" src="https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=828&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=828&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=828&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1040&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1040&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446935/original/file-20220217-27-tcgdni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1040&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Messmate stringybark (Eucalyptus obliqua) in southern Tasmania.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>But this is no longer the case. </p>
<p>I monitored what happened to a messmate stringybark (<em>Eucalyptus obliqua</em>) forest during a three week heatwave in November 2017. Under these conditions, the forest became a net source of carbon dioxide, with each hectare releasing close to 10 tonnes of the greenhouse gas over that period. </p>
<p>A year earlier during more normal conditions, the forest was a net sink for carbon dioxide, taking in around 3.5 tonnes per hectare. </p>
<p>How can we know this? The forest I studied is at the Warra Supersite in the upper reaches of the Huon Valley, one of 16 intensive ecosystem monitoring field stations making up Australia’s <a href="https://www.tern.org.au/">Terrestrial Ecosystem Research Network</a>.</p>
<p>Instruments mounted on an 80-metre-tall tower at Warra give us great insight into how the forest is behaving. We can measure how much, and how quickly, carbon dioxide, water and energy shuttle between the forest and the atmosphere.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australian-forests-will-store-less-carbon-as-climate-change-worsens-and-severe-fires-become-more-common-173233">Australian forests will store less carbon as climate change worsens and severe fires become more common</a>
</strong>
</em>
</p>
<hr>
<p>So what actually happened in the forest during the hot spell? Two crucial things. </p>
<p>The first was that the forest breathed out more carbon dioxide. This was expected, because living cells in all air-breathing lifeforms (yes, this includes trees)
respire more as temperatures warm. </p>
<p>But the second was very unexpected. The forest’s ability to photosynthesise fell, meaning less solar energy was converted to sugars. This took place while the trees were transpiring (releasing water vapour) rapidly. </p>
<p>Until now, we’ve seen falls in photosynthesis output in heatwaves because the trees are trying to limit their water loss. They can do this by closing their pores on their leaves (stomata). When a tree closes its stomata, it makes it harder for carbon dioxide in air to enter the leaves and fuel the photosynthesis process. </p>
<p>By contrast, this heatwave saw trees releasing water and producing less food at the same time. </p>
<p>So what’s going on? In short, the temperatures were simply too hot for the forests in southern Tasmania. Every forest has an ideal temperature to get the best results from photosynthesis. We now know this temperature in Australia is <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15760">linked to the historic climate</a> of the local area. </p>
<p>That means the trees at Warra require lower temperatures to optimally feed themselves, compared to most other Australian forests. </p>
<p>During the 2017 heatwave, the temperatures soared well outside the forest’s comfort zone. In the hottest part of the day, the forest was no longer able to make enough food to feed itself. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="River and forest in Tasmania" src="https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446950/original/file-20220217-24-1c9xibt.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"></a>
<figcaption>
<span class="caption">For now, the forests at Warra remain intact.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Outside the forest’s comfort zone</h2>
<p>For now, the forest at Warra is still intact. After the heatwave, the messmate stringybark forest quickly recovered its ability to feed itself, and became a carbon sink again. </p>
<p>But as the world warms, these forests will be pushed outside their comfort zones more and more. They can only endure so many of these kinds of heatwaves. If they keep coming, there will be a <a href="https://www.science.org/doi/full/10.1126/sciadv.aay1052">tipping point</a> beyond which the forest can no longer recover. </p>
<p>What then? We can see a disturbing glimpse when we look at Tasmania’s oceans, which are a marine heatwave hotspot. Fully 95% of Tasmania’s giant kelp forests are now gone, <a href="https://www.int-res.com/articles/feature/m653p001.pdf">killed off</a> by temperatures beyond their ability to tolerate. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="giant kelp forest" src="https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446944/original/file-20220217-22-1kzkp2p.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">Giant kelp forests are all but gone from Tasmanian waters.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>It is no exaggeration to say that the rapid increase in temperatures are the most serious threat to the health of tall eucalypt forests I’ve encountered during 40 years of studying forest health and threats in Tasmania. </p>
<p>Unlike the kelp forests, our tall eucalyptus forests have not yet hit their tipping point. We still have time to lessen the risk global heating poses. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/can-selective-breeding-of-super-kelp-save-our-cold-water-reefs-from-hotter-seas-170271">Can selective breeding of 'super kelp' save our cold water reefs from hotter seas?</a>
</strong>
</em>
</p>
<hr>
<p>There is already work under way to test promising new methods for making future forests better able to cope with the new climate they find themselves in. </p>
<p>These techniques include <a href="https://www.frontiersin.org/articles/10.3389/fevo.2015.00065/full">climate adjusted provenancing</a>, where forest managers sow seeds of local species collected from areas at the hotter end of their range. Another being tried for giant kelp is <a href="https://www.nespmarine.edu.au/system/files/Layton%20et%20al_E7_M5_Assessing%20the%20feasibility%20of%20restoring%20giant%20kelp%20forests%20in%20Tas.pdf">finding individual plants</a> with better heat tolerance and breeding them. </p>
<p>Our eucalyptus forests will need our help, more and more. The better engaged and informed we are about the risks to forests we long thought were highly resilient, the likelier we will be to be able to preserve them. </p>
<p>One way we could do this is by making our monitoring data publicly accessible in real time, so we can grasp the strain our forests are under as the world warms.</p><img src="https://counter.theconversation.com/content/176979/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tim Wardlaw is affiliated with the Terrestrial Ecosystem Research Network.</span></em></p>Southern Tasmania’s cool climate was thought to be a climate refuge for tall forests. But that may no longer be true.Tim Wardlaw, Research Associate, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1757832022-02-02T16:52:03Z2022-02-02T16:52:03ZCurious Kids: what do plants do all day?<figure><img src="https://images.theconversation.com/files/443822/original/file-20220201-13-df60fw.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7987%2C5328&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/little-african-american-kid-boy-look-1841045359">Roman Chazov/Shutterstock</a></span></figcaption></figure><p><strong>What do plants do all day? – Oliver, aged almost three, Kent, England</strong></p>
<p>It is easy to think that the daily life of a plant is a simple one. They seem to just stand there and sunbathe. However, plants are very busy all the time doing many things. This activity is aimed at surviving the day and planning for the future.</p>
<p>Plants need food to survive. Being rooted in the ground means that they can’t move around to find food, so they must make their own. </p>
<p>They do this by taking water from the soil in through their roots and a molecule in the air, carbon dioxide, into their leaves. They then use the energy from sunlight which they absorb into their leaves to combine the water and carbon dioxide to make complex sugar molecules – food.</p>
<p>This process, called <a href="https://www.bbc.co.uk/bitesize/clips/z2k4d2p">photosynthesis</a>, is one of the most amazing chemical reactions on the planet.</p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&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><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>The plant then does one of two things with these sugar molecules. It can use them in <a href="https://www.bbc.co.uk/bitesize/topics/zvrrd2p/articles/zjqfsk7">respiration</a>. This is a process that releases the energy of the sugar molecules to allow the plant to do its daily activities. It can also convert the sugar molecules into other more complex chemicals to build other plant parts, such as new leaves or flowers.</p>
<p>However, the chemicals that are used to make up plant parts need more than just the input of sunlight, water and carbon dioxide. They also need additional chemicals that they take from the soil. It is the same as humans needing a healthy diet. </p>
<p>So, the plant spends all day mining the soil for useful chemicals such as nitrates, phosphates and various metals. These must then be moved to the part of the plant where they are needed. </p>
<h2>Measuring light</h2>
<p>Every day, plants must measure the <a href="https://www.adonline.id.au/flowers/photoperiod/">amount of daylight</a> they are getting. In particular, they need to know whether the hours of daylight are getting less or more from one day to the next. Measuring this change allows the plant to recognise what time of year it is. If daylight is increasing, then it knows that it is spring and time to start producing flowers. </p>
<figure class="align-center ">
<img alt="Meadow of purple crocus" src="https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=475&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=475&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=475&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=597&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=597&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444023/original/file-20220202-25-g3nn09.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=597&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Measuring light helps a plant know when to produce spring flowers.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/blossom-crocuses-spring-mountains-colorful-sunset-253469935">Andrew Mayovskyy/Shutterstock</a></span>
</figcaption>
</figure>
<p>If daylight is getting less then the plant knows that winter is coming. It can put food into storage ready for next spring’s growth. For example, daffodils produce bulbs, and the potato plant makes tubers – which are the potatoes that we eat.</p>
<p>It can also get rid of things it will not need in the winter. Oak trees do not use leaves to make food during the winter, as there isn’t enough light. So, the leaves fall off its branches and grow again in spring. </p>
<p>While a plant is always keeping track of how much of the 24-hour period is daylight, a term scientists call light quantity, it also monitors any <a href="https://www.hhmi.org/news/made-shade-how-plants-can-beat-competition">changes in light quality</a>. </p>
<p>This is the type of light falling on the plant. It might be full sunlight, or it might be light that is filtered through the leaves of other plants. If the plant is not getting the right light quality, it means it is being shaded by other plants. It must either start growing taller to find the full sun again, or produce larger leaves to gather in more light.</p>
<h2>Staying healthy</h2>
<p>The plant also monitors its own health. If a plant is being eaten by insects, it can produce a set of chemicals to make its leaves <a href="https://www.bbc.co.uk/bitesize/guides/z29trwx/revision/3">less tasty</a>. </p>
<figure class="align-center ">
<img alt="Caterpillar eating leaf" src="https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444021/original/file-20220202-17-rafz1r.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">Plants can produce chemicals to protect themselves from insects.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/caterpillar-eating-green-leaf-129550835">Bahadir Yeniceri/Shutterstock</a></span>
</figcaption>
</figure>
<p>We also know that plants that have detected they are being eaten can release chemicals into the air to warn its neighbours, and let them know that they should start making their leaves less tasty. </p>
<p>The same applies if fungal disease strikes the plant. The plant produces chemicals to attack the fungus and seals off parts of the plant that are damaged too much to be repaired. </p>
<p>So, every day, plants are making food, extracting minerals so they can grow, working out what season it is and whether they are getting enough light, and protecting themselves from animals that want to eat them – as well as warning their neighbours. It makes for a busy day, although one that is largely invisible to humans.</p><img src="https://counter.theconversation.com/content/175783/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Ashton 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>Though you might not think so to look at them, plants have a busy day.Paul Ashton, Head of Biology, Edge Hill UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1693372022-01-17T13:16:08Z2022-01-17T13:16:08ZWhy do plants grow straight?<figure><img src="https://images.theconversation.com/files/438139/original/file-20211216-19-1l3wauj.jpg?ixlib=rb-1.1.0&rect=12%2C0%2C2032%2C1523&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">_Allium schoenoprasum_, better known as chives.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/Tvikbd">Andreas Rockstein/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&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><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p>Why do plants grow straight? – Sara H., age 5, New Paltz, New York</p>
</blockquote>
<hr>
<p>Have you ever been at a sporting event or concert and had to wiggle and reposition to get in just the right spot to see the action? Maybe you needed to shift left or right to see between two people. Perhaps you even had to squat on your seat to see over the person in front of you.</p>
<p>Well, plants often have to do something similar so that they can “see” as much light as possible. Plants need light to perform photosynthesis – making sugars from water and carbon dioxide in the air to feed themselves.</p>
<p>If sunlight is directly above them, then plants will grow straight up toward it. </p>
<p>Sometimes, though, it’s not that simple. For example, you might have seen house plants bending towards a window rather than growing straight and tall. When light comes from an angle, plants will curve toward it to get better access to the light they need to grow. Hormones in the plant’s tissues, called <a href="https://www.britannica.com/science/auxin">auxins</a>, make cells on the dark side of the plant grow taller, bending the plant toward the light. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/HmHvWDeTt7Y?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Plants contain hormones called auxins that make them grow in the direction of light sources.</span></figcaption>
</figure>
<p>In a forest, plants may branch out so that their leaves are in open patches of sun, rather than in the shade. This often happens if taller bushes and trees tower over them, or if they are growing in a crowd of other plants. It’s much like humans seeking out sunny spots or reaching their hands toward a campfire to warm up when they feel cold outdoors.</p>
<p>[<em>More than 140,000 readers get one of The Conversation’s informative newsletters.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140K">Join the list today</a>.]</p>
<p>Humans twist or bend by changing our body positions temporarily, but when plants twist, bend or elongate, they are actually growing toward the light. The types of plants that reposition themselves to see the light are species that grow in a slow but determined way.</p>
<p>Other types of plants may not grow straight because they have different strategies. For example, strawberries grow close to the ground and spread sideways by sending out <a href="https://kids.britannica.com/kids/article/strawberry/433049">runners</a> – stems that spread out just above the ground to create new plants. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Stone house with ivy reaching up one wall to second story." src="https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438143/original/file-20211216-13-fq1fxz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ivy is climbing up the side of this house in Aberdeen, Scotland, to expose its leaves to as much sun as possible.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/2QJYU">Stuart Caie/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Other plants, like ivy, grow as vines that climb up trees, walls and fences and use them for support. Climbing vines may grow straight, to the side or at angles, depending on what kinds of support structures they find to grow on. The purpose is to expose their leaves to as much sunlight as possible.</p>
<p>In my recent book, “<a href="https://www.hup.harvard.edu/catalog.php?isbn=9780674241282">Lessons from Plants</a>,” I explore how plants are usually positioning themselves to see the light. It’s fascinating that we humans, too, are often positioning ourselves to see something interesting. </p>
<p>So the next time you see a plant growing straight, take notice of whether light is directly above it. Or if you see a plant that’s not straight, notice whether it’s bending toward light coming from the direction it’s facing. Or maybe it’s a vine climbing on a structure and using that support to take a different route toward the sun.</p>
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<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/169337/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Beronda L. Montgomery receives funding from National Science Foundation, grant no. MCB-1515002 to BLM.</span></em></p>Plants need light to feed themselves, so they grow in ways that help them collect as much of it as they can. Sometimes that’s straight up, but not always.Beronda L. Montgomery, Professor of Biochemistry and Molecular Biology & Microbiology and Molecular Genetics, and Assistant Vice President of Research & Innovation, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1747522022-01-12T13:38:21Z2022-01-12T13:38:21ZFive fascinating insights into the inner lives of plants<figure><img src="https://images.theconversation.com/files/440454/original/file-20220112-25-zmd311.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7289%2C4772&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/young-plant-growing-sunlight-609086588">Romolo Tavani/Shutterstock</a></span></figcaption></figure><p>Approximately 4.5 billion years ago, Earth’s land surface was barren and devoid of life. It would take another 2 billion years for the first single-celled organisms to appear in the ocean, including the first algae <em><a href="http://www.jsjgeology.net/Grypania-spiralis.htm">Grypania spiralis</a></em>, which was about the size of a 50 pence piece.</p>
<p>Plants composed of many cells have only been around for a mere 800 million years. To survive on land, plants had to protect themselves from UV radiation and develop spores and later seeds which allowed them to disperse more widely. These innovations helped plants become one of the most influential lifeforms on Earth. Today, plants are found in every major ecosystem on the planet and scientists describe more than 2,000 new species every year.</p>
<p>David Attenborough’s new documentary <a href="https://www.bbc.co.uk/programmes/m0013cl7">The Green Planet</a> casts the spotlight on plants and their ability to inspire us. In just one recent example, engineers have successfully mimicked the shape of winged maple seeds <a href="https://www.semanticscholar.org/paper/Maple-Seed-Performance-as-a-Wind-Turbine-Holden-Caley/4f5e2060500f2cd06ab63bbdf74024fdbf0c0f16">to design</a> new wind turbines.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/BoKyMzsa4Xs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>Plants retain many secrets which scientists have yet to discover. But here are five discoveries which helped us see our distant green cousins in a new light.</p>
<h2>1. Plants ‘talk’ to each other</h2>
<p>Of course, plants do not possess vocal cords and so cannot talk like we do. But they do use chemical and electronic signals to coordinate responses to their environment.</p>
<p>When plant cells are damaged, like grass cut by a lawnmower, they release protein fragments which can be detected by surrounding plants. It’s like a neighbourhood watch system: when one plant is harmed, the others are notified that there is danger nearby. This can trigger an immune response or other defences.</p>
<p>Similarly, plants can detect pollinators in their vicinity and release chemicals to attract them. These signals make plants very complex communicators.</p>
<figure class="align-center ">
<img alt="A tropical flowering plant covered in large, green ants." src="https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/440452/original/file-20220112-21-ughdth.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 can attract insects to do their bidding.</span>
<span class="attribution"><span class="source">Thom Dallimore</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>2. Plants can move</h2>
<p>In his seminal book <a href="https://www.cambridge.org/core/books/power-of-movement-in-plants/9B9B104AB3638E43936A34F1FB73E393">The Power of Movement in Plants</a>, published in 1880, Charles Darwin described the ability of plants to move away or towards light. Scientists call this phototropism. Plant movements are now known to not only be guided by light, but also water, nutrients and in response to grazing by animals and competition from other plants. </p>
<p>Plants may appear frozen in place, destined to remain where their seeds germinate. But in fact, plants constantly adjust their leaves, roots and stems to improve their chances of survival. For example, the shaded sides of stems always grow longer to ensure the plant grows towards light in a process mediated by hormones. Roots show the opposite effect, causing them to grow away from the light. </p>
<p>In some extreme cases, plants can even move across an entire forest. Nomadic vines grow upwards from the bottom of a tree trunk then detach from the soil. Later, they put down aerial roots and descend again, allowing them to <a href="https://www.jstor.org/stable/2261006?seq=1#metadata_info_tab_contents">move between trees</a>.</p>
<h2>3. Plants can grow in outer space</h2>
<p>The idea of traversing space and living on other planets has long excited the human imagination. But no planets with the same environment as Earth have been found. We know plants are experts at modifying environments to suit the needs of more complex life. As early forests began photosynthesising, they oxygenated Earth’s atmosphere and drew down CO₂, making the planet more hospitable.</p>
<p>Could growing plants on distant planets make them more suitable to our needs? During the space race between the USSR and the US in the 1950s and 1960s, scientists studied how plants grow and develop in space. So far, scientists have grown 17 different species of plants in specialised chambers, including crops like <a href="https://www.nasa.gov/feature/nasa-astronaut-paints-a-picture-of-success-growing-plants-in-space">corn, wheat, tomatoes and lettuce</a>. Big challenges to growing Earth’s plants outside our atmosphere remain, including radiation during space flight and differences in gas movements in space compared to Earth. If you think it’s hard to keep a plant alive at home, try doing it in space.</p>
<p>The ability to terraform a planet – making it suitable for humans to live on – remains elusive. But major progress in plant science over the last few years make this an achievable target, perhaps within the lifetime of people alive today.</p>
<h2>4. One in ten plants grow on other plants</h2>
<p>Often towering tens of metres tall are some of the largest organisms on the planet. Redwood trees, for example, can grow over 100 metres tall. Scientists first began studying their lofty forest canopies by training monkeys or employing skilled climbers to collect samples. Some even used shotguns to shoot down samples. </p>
<p>It was not until the 1980s that canopy research became a scientific discipline in its own right, with the use of rope climbing techniques borrowed from mountaineering. Later, cranes, balloons and drones joined the toolset of many scientists. But why risk your life to climb a tree? What’s up there? </p>
<p>It’s estimated that up to <a href="https://www.sciencedirect.com/science/article/pii/S0169534717300599">80% of species</a> in a forest either use or live their entire lives in the forest canopy. One in ten of all known species of vascular plants – species which use vein-like vessels to transport water and nutrients throughout their body – grow on top of other plants. </p>
<figure class="align-center ">
<img alt="A tree whose bark is concealed by green and fuzzy plants growing on its surface." src="https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/440453/original/file-20220112-21-1khse3w.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A tree in Papua New Guinea covered in epiphytic ferns and orchids.</span>
<span class="attribution"><span class="source">Thom Dallimore</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>These are called epiphytes. They are not parasites, but instead use their host for physical support. This gives them an advantage over plants growing in the forest understorey, where light is scarce. Most orchids grow on trees and a single tree can hold as many as 50 species of epiphyte. Often, these epiphytes put out more leaves than their host tree. </p>
<h2>5. Plants can indicate global change</h2>
<p>Organisms are very sensitive to changes in their environment and plants in particular have been used to detect these changes for centuries. When leaves start to change colour in autumn, it usually heralds the arrival of cooler and darker months. </p>
<p>Certain species of ferns are particularly vulnerable to changes in their local climate. Filmy ferns grow in shaded regions of tropical forests, usually near the bases of trees or on wet rocks. They rely on water and low temperatures, and are good indicators of oncoming drought and rising temperatures.</p>
<p>Since the 1980s, the global average temperature has been rising as a direct result of burning fossil fuels like coal, which was deposited by plants millions of years ago during the early formation of forests. We are living in a time of change and understanding how plants respond to changes in climate can help us to prepare ourselves for the future.</p><img src="https://counter.theconversation.com/content/174752/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sven Batke 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>David Attenborough’s new BBC documentary The Green Planet shows plants are stranger than they first appear.Sven Batke, Lecturer in Biology, Edge Hill UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1718082021-11-15T01:31:59Z2021-11-15T01:31:59ZAntarctic bacteria live on air and make their own water using hydrogen as fuel<figure><img src="https://images.theconversation.com/files/431840/original/file-20211114-21-10bd85o.jpeg?ixlib=rb-1.1.0&rect=13%2C13%2C2982%2C2232&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Ian Hogg</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Humans have only recently begun to think about using hydrogen as a source of energy, but bacteria in Antarctica have been doing it for a billion years. </p>
<p><a href="https://doi.org/10.1073/pnas.2025322118">We studied 451 different kinds of bacteria</a> from frozen soils in East Antarctica and found most of them live by using hydrogen from the air as a fuel. Through genetic analysis, we also found these bacteria diverged from their cousins in other continents approximately a billion years ago.</p>
<p>These incredible microorganisms come from ice-free desert soils north of the Mackay Glacier in East Antarctica. Few higher plants or animals can prosper in this environment, where there is little available water, temperatures are below zero, and the polar winters are pitch-black.</p>
<p>Despite the harsh conditions, microorganisms thrive. <a href="https://doi.org/10.1093/femsec/fiw126">Hundreds of bacterial species</a> and <a href="https://doi.org/10.1007/s00792-002-0276-5">millions of cells</a> can be found in a single gram of soil, making for a unique and diverse ecosystem.</p>
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<a href="https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431843/original/file-20211114-13-y0yaem.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The freezing soil of Antarctica makes a surprising home for a diverse community of microbes that have adapted to life in the harsh conditions.</span>
<span class="attribution"><span class="source">Ian Hogg</span>, <span class="license">Author provided</span></span>
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<p>How do microbial communities survive in such punishing surroundings?</p>
<h2>A dependable alternative to photosynthesis</h2>
<p>We discovered more than a quarter of these Antarctic soil bacteria create an enzyme called RuBisCO, which is what lets plants use sunlight to capture carbon dioxide from air and convert it into biomass. This process, photosynthesis, generates most of the organic carbon on Earth. </p>
<p>However, we found more than 99% of the RuBisCO-containing bacteria were unable to capture sunlight. Instead, they perform a process called chemosynthesis. </p>
<p>Rather than relying on sunlight to power the conversion of carbon dioxide into biomass, they use inorganic compounds such as the gases hydrogen, methane, and carbon monoxide.</p>
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Read more:
<a href="https://theconversation.com/extremophiles-resilient-microorganisms-that-help-us-understand-our-past-and-future-165634">Extremophiles: resilient microorganisms that help us understand our past - and future</a>
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<h2>Living on air</h2>
<p>Where do the bacteria find these energy-rich compounds? Believe it or not, the most reliable source is the air! </p>
<p>Air contains high levels of nitrogen, oxygen and carbon dioxide, but also trace amounts of the energy sources hydrogen, methane, and carbon monoxide. </p>
<p>They are only present in air in very low concentrations, but there is so much air it provides a virtually unlimited supply of these molecules for organisms that can use them.</p>
<p>And many can. Around 1% of Antarctic soil bacteria can use methane, and some 30% can use carbon monoxide.</p>
<p>More remarkably, our research suggests that 90% of Antarctic soil bacteria may scavenge <em>hydrogen</em> from the air. </p>
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<img alt="" src="https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431844/original/file-20211114-27-ajhz3n.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Only a tiny fraction of air is hydrogen, but there’s so much air it makes an unlimited supply of fuel for bacteria that can harvest it.</span>
<span class="attribution"><span class="source">Ian Hogg</span>, <span class="license">Author provided</span></span>
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<p>The bacteria gain energy from hydrogen, methane and carbon by combining them with oxygen in a chemical process that is like a very slow kind of burning.</p>
<p>Our experiments showed the bacteria consume atmospheric hydrogen even at temperatures of -20°C, and they can consume enough to cover all their energy requirements. </p>
<p>What’s more, the hydrogen can power chemosynthesis, which may provide enough organic carbon to sustain the entire community. Other bacteria can access this carbon by “eating” their hydrogen-powered neighbours or the carbon-rich ooze they produce.</p>
<h2>Water from thin air</h2>
<p>When you burn hydrogen, or when the bacteria harvest energy from it, the only by-product is water. </p>
<p>Making water is an important bonus for Antarctic bacteria. They live in a hyper-arid desert, where water is unavailable because the surrounding ice is almost permanently frozen and any moisture in the soil is rapidly sucked out by the dry, cold air.</p>
<p>So the ability to generate water from “thin air” may explain how these bacteria have been able to exist in this environment for millions of years. By our calculations, the rates of hydrogen-powered water production are sufficient to rehydrate an entire Antarctic cell within just two weeks.</p>
<p>By adopting a “hydrogen economy”, these bacteria fulfil their needs for energy, biomass, and hydration. Three birds, one stone.</p>
<h2>Could a hydrogen economy sustain extraterrestrial life?</h2>
<p>The minimalist hydrogen-dependent lifestyle of Antarctic soil bacteria redefines our understanding of what is the very least required for life on Earth. It also brings new insights into the search for extraterrestrial life.</p>
<p>Hydrogen is the most common element in the universe, making up almost three-quarters of all matter. It is a major component of the atmosphere on some alien planets, such as <a href="https://doi.org/10.1051/0004-6361/200913347">HD 189733b</a> which orbits a star 64.5 light-years from Earth. </p>
<p>If life were to exist on such a planet, where conditions may not be as hospitable as on much of Earth, consuming hydrogen might be the simplest and most dependable survival strategy.</p>
<p>“Follow the water” is the mantra for searches of extraterrestrial life. But given bacteria can literally make water from air, perhaps the key to finding life beyond Earth is to “follow the hydrogen”.</p>
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<strong>
Read more:
<a href="https://theconversation.com/hydrogen-breathing-aliens-study-suggests-new-approach-to-finding-extraterrestrial-life-137630">Hydrogen-breathing aliens? Study suggests new approach to finding extraterrestrial life</a>
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<img src="https://counter.theconversation.com/content/171808/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Greening receives funding from the Australian Research Council, the Australian Antarctic Science Program, the National Health & Medical Research Council, and the Wellcome Trust.</span></em></p><p class="fine-print"><em><span>Steven Chown receives funding from the Australian Research Council, the Australian Antarctic Science Program, the National Health & Medical Research Council and the Wellcome Trust. He is Immediate Past President of the Scientific Committee on Antarctic Research.</span></em></p><p class="fine-print"><em><span>Pok Man Leung 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>A billion-year-old ‘hydrogen economy’ in the frozen soil of Antarctica provides bacteria with energy, water, and the carbon that makes up their bodies.Pok Man Leung, PhD candidate in Microbiology, Monash UniversityChris Greening, Associate professor, microbiology, Monash UniversitySteven Chown, Director, Securing Antarctica's Environmental Future, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1651482021-08-12T07:59:04Z2021-08-12T07:59:04ZHumans will always have oxygen to breathe, but we can’t say the same for ocean life<p>There is nothing more fundamental to humans than the availability of oxygen. We give little thought to the oxygen we need, we just breathe, but where does it come from?</p>
<p>To shed light on this, statements such as “the ocean provides 50% of the oxygen we breathe”, or its equivalent, “every second breath we breathe comes from the ocean”, have become common mantras to highlight human dependence on the ocean and the risk of lower oxygen supply due to climate change and environmental degradation.</p>
<p>These mantras are repeated by high-profile politicians, including US climate envoy <a href="https://www.state.gov/special-guest-remarks-at-ocean-climate-ambition-summit/">John Kerry</a> and French president <a href="https://www.elysee.fr/emmanuel-macron/2019/12/03/locean-poumon-de-lhumanite-qui-menace-de-setouffer">Emmanuel Macron</a>, international organisations such as <a href="https://en.unesco.org/themes/preserving-ocean">Unesco</a> and the <a href="https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52020DC0259">European Commission</a>, and even prominent reports from the <a href="https://ocean-climate.org/en/press-release-the-ipcc-adopts-the-special-report-on-the-ocean-and-cryosphere-in-a-changing-climate/">IPCC</a> and other reputable <a href="https://oceanservice.noaa.gov/news/june14/30days.html">scientific institutions</a>.</p>
<p>While they may be good fodder for speeches, these claims misrepresent where the oxygen we breathe actually comes from, and in doing so, mislead the public as to why we should step up our role as ocean custodians.</p>
<h2>Where do we get our oxygen?</h2>
<p>The Earth’s atmosphere has <a href="https://doi.org/10.1038/nature13068">not always been as rich in oxygen as it is today</a>. The atmosphere is now made up of <a href="https://climate.nasa.gov/news/2491/10-interesting-things-about-air/">21% oxygen</a>, but it accounted for just 0.001% of today’s levels during the first 2 billion years of Earth’s history.</p>
<p>It is the advent of microscopic ocean bacteria and plants (phytoplankton) and, later, larger plants on land which caused the staggering increase of oxygen in our atmosphere. This oxygen is derived from <a href="https://www.nationalgeographic.org/encyclopedia/photosynthesis/">photosynthesis</a> – the process by which plants turn carbon dioxide and water into organic matter and oxygen.</p>
<p>Oxygen has been relatively stable at a high level for the past 500 million years. Today, <a href="https://doi.org/10.1126/science.281.5374.237">roughly half of photosynthesis takes place in the ocean and half on land</a>.</p>
<p>So yes, the ocean is responsible for about 50% of the oxygen produced on the planet. But it’s not responsible for 50% of the air we humans breathe. Most of the oxygen produced by the ocean is directly consumed by the microbes and animals that live there, or as plant and animal products fall to the seafloor. In fact, the net production of oxygen in the ocean is close to 0.</p>
<figure class="align-center ">
<img alt="Figure legend. Oxygen budget for the period 1960-2014 (redrawn from Grégoire et al., 2019)" src="https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=319&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=319&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=319&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=401&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=401&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415498/original/file-20210810-21-1vkqtv5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=401&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Oxygen produced by photosynthesis (i.e. net primary production) in the upper ocean is roughly consumed by respiration within the water column, except for a small excess production of 0.002 Pmol O2 per year which corresponds to burial in the ocean floor.</span>
<span class="attribution"><span class="source">Redrawn from Grégoire et al., 2019</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>A tiny fraction of the primary production, roughly 0.1%, escapes degradation and is stored as organic carbon in marine sediments – a process referred to as the <a href="https://rapid.ac.uk/abc/bg/bcp.php">biological carbon pump</a>. This organic carbon may eventually turn into fossil fuels such as coal, oil and gas. The tiny amount of oxygen which had been generated to produce this carbon store can later be released to the atmosphere. A similar process occurs on land too, with some carbon stored in soils.</p>
<p>Therefore, the oxygen we currently breathe comes from the slow accumulation of O₂ in the atmosphere supported by the burial of organic matter over very long time-scales – hundreds of millions of years – and not from the contemporary production by either the land or ocean biosphere.</p>
<h2>Fossil fuels and the air we breathe</h2>
<p>How about future trends of atmospheric oxygen? As early as 1970, the prominent geochemist <a href="https://doi.org/10.1126/science.168.3939.1537">Wally S Broecker recognised</a> that if we were to burn all known fossil fuel reserves, we would use up less than 3% of our oxygen reservoir.</p>
<p>If we were to cut or burn all forests and oxidise all organic carbon stored in vegetation and top soils worldwide, it would only lead to a small depletion in atmospheric oxygen. If photosynthesis in the ocean and on land stopped producing oxygen, we could continue breathing for millennia, though we would certainly have other problems.</p>
<p>The projected decline in atmospheric oxygen, even in the worst-case scenarios with massive fossil fuel burning and deforestation, will be very small relative to the very large atmospheric reservoir. <a href="http://www.nature.com/doifinder/10.1038/ngeo420">Models</a> show that the content of oxygen in the atmosphere will experience a minute change over the next 100,000 years in response to fossil fuel use. So while there are <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">many things to worry about in our climate future</a>, the availability of oxygen for air-breathing organisms (including humans) isn’t one of them.</p>
<h2>Oxygen decline in the ocean</h2>
<p>There are significant <a href="https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/">causes for concern</a> regarding the content of oxygen in the ocean, however. The ocean’s O₂ reservoir is vulnerable because it holds less than 1% of the oxygen stored in the atmosphere. In particular, ocean regions with very low or absent oxygen, referred to as <a href="https://depts.washington.edu/aog/oxygen-minimum-zones/">oxygen minimum zones</a>, expand as the planet warms, making new regions inhabitable for breathing organisms like fish.</p>
<p>The open ocean lost <a href="https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/">0.5 to 3.3% of its oxygen stock</a> in the top 1000 metres from 1970-2010, and the volume of oxygen minimum zones has increased by 3-8%.</p>
<p>This oxygen loss is primarily due to increasing <a href="https://www.nature.com/articles/s41558-020-00918-2">ocean stratification</a>. In this process, the mixing of the surface ocean, which becomes warmer and lighter, with the deeper and denser ocean layers is less efficient, restricting the penetration of oxygen. The activity of enzymes, including those involved in respiration, also generally increases with temperature. So, oxygen consumption by ocean creatures increases as the ocean warms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Phytoplankton and blue-green algae blooms in Finland" src="https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415506/original/file-20210810-15-1fmjpnd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most of the oxygen produced by the ocean is directly consumed by the microbes and animals that live there.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/seandoran/42685457065">Sean Doran</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>A recent <a href="https://doi.org/10.1126/science.aam7240">study</a> found that oxygen minimum zones in the open ocean have expanded by several million square kilometres and hundreds of coastal sites now have oxygen concentrations low enough to limit animal populations and alter the cycling of important nutrients. The volume of low-oxygen areas is projected to <a href="https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/">grow by about 7%</a> by 2100 under a scenario of high-CO₂ emissions.</p>
<p>Deoxygenation of this kind affects biodiversity and food webs; and negatively affects food security and livelihoods of the people who depend on it.</p>
<h2>The facts</h2>
<p>So where does this leave our mantra?</p>
<p>While it is incorrect to say that the ocean provides 50% of the oxygen we breathe, it is correct to say that, over geological time scales, the ocean has provided a large fraction of the oxygen we take in today. It is also perfectly correct to say that the ocean is responsible for 50% of primary production on Earth, sustaining our food system.</p>
<p>And while we should not worry about the future supply of oxygen for humans to breathe in the future, we should worry about fish being increasingly displaced from expanding ocean areas that are depleted in oxygen.</p><img src="https://counter.theconversation.com/content/165148/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jean-Pierre Gattuso's recent research was partly supported by the Prince Albert II of Monaco Foundation, the Ocean Acidification International Coordination Centre of the International Atomic Energy Agency, the Veolia Foundation, the French Facility for Global Environment, the French Polar Institute and the European Commission.</span></em></p><p class="fine-print"><em><span>Carlos M. Duarte a reçu des financements de King Abdullah University of Science and Technology and Oceans2050.</span></em></p><p class="fine-print"><em><span>Fortunat Joos is a researcher at Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research at the University of Bern. He acknowledges funding from the Swiss National Science Foundation (#200020_200511 ) and from the European Union’s Horizon 2020 research and innovation programme under grant agreements No 820989 (project COMFORT) and No 821003 (project 4C). The work reflects only the authors’ view; the European Commission and their executive agency are not responsible for any use that may be made of the information the work contains.</span></em></p><p class="fine-print"><em><span>Laurent Bopp's recent research was supported by CNRS, by the French Foundation for Biodiversity Research (FRB), by the European Union's Horizon 2020 research programme, and by Chanel through a Research Chair. </span></em></p>We are not at risk of running out of oxygen due to climate change, but ocean creatures are – and that will harm the whole planet.Jean-Pierre Gattuso, Research Professor, CNRS, Iddri, Sorbonne UniversitéCarlos M. Duarte, Distinguished Professor of Marine Science, King Abdullah University of Science and TechnologyFortunat Joos, Professor, University of BernLaurent Bopp, Research Professor, CNRS, École normale supérieure (ENS) – PSLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1518652020-12-10T19:12:56Z2020-12-10T19:12:56ZCarbon dioxide feeds plants, but are earth’s plants getting full?<figure><img src="https://images.theconversation.com/files/374249/original/file-20201210-19-57lrge.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">lowpower225 / shutterstock</span></span></figcaption></figure><p>Plants do a lot of work for us, producing the air we breathe, the food we eat, and even some of our medicine. But when it comes to removing carbon dioxide in the atmosphere, we may have been overestimating their ability.</p>
<p>Photosynthesis acts as the lungs of our planet – plants use light and carbon dioxide (CO₂) to make the sugars they need to grow, releasing oxygen in the process. When atmospheric CO₂ concentrations increase, as they have been thanks to humans burning fossil fuels, one might think that plants are enjoying a smorgasbord of food for unlimited growth. But a new study published in <a href="https://science.sciencemag.org/cgi/doi/10.1126/science.abb7772">Science</a> shows this excess of riches is not as effective as previously thought. </p>
<p>Since CO₂ is the main source of food for plants, increasing levels of it directly stimulate the photosynthetic rate of most plants. This <a href="https://www.nature.com/articles/nature22030">boost in photosynthesis</a>, known as the “CO₂ fertilisation effect”, enhances growth in many of earth’s plant species, with the effects seen most clearly in <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15375">crops</a> and young trees, and less so in <a href="https://www.nature.com/articles/s41586-020-2128-9?proof=trueHere">mature forests</a>. </p>
<p>The amount of CO₂ used by photosynthesis and stored in vegetation and soils has grown over the past <a href="https://theconversation.com/yes-more-carbon-dioxide-in-the-atmosphere-helps-plants-grow-but-its-no-excuse-to-downplay-climate-change-130603">50 years</a>, and now absorbs at least a quarter of human emissions in an average year. We’ve been assuming that this benefit will continue to increase as CO₂ concentrations rise, but data collected over a 33-year period show us that might not be true.</p>
<h2>Fertilisation is in decline</h2>
<p>Estimating the size of the global CO₂-fertilisation effect accurately is no easy task. We have to understand what limits photosynthesis from one region to another, and at every scale from molecules within a leaf through to whole ecosystems.</p>
<p>The big research team behind the new Science study used a combination of data from satellites and on-the-ground observations and models of the carbon cycle. Using this powerful toolkit, they found that the fertilisation effect declined across much of the globe from 1982 to 2015 – a trend that correlates well with observed changes in <a href="https://www.nature.com/articles/s41559-018-0694-0">nutrient concentrations</a> and available <a href="https://www.nature.com/articles/nclimate2995">soil water</a>.</p>
<p>In many ways, the combination of these different tools helps to paint a more complete picture of how the world’s ecosystems are photosynthesising. The researchers <a href="https://www.nature.com/articles/s41597-020-0534-3">used</a> a collection of long-term measurements from <a href="https://fluxnet.org/about/">flux towers</a> like the one pictured below which continuously monitor the CO₂ and water used by plants and are dotted across earth’s biomes and provide the best means of measuring photosynthesis at the ecosystem scale. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Some scientific equipment in a field." src="https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/374251/original/file-20201210-15-19oyvmb.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">FLUXNET towers around the world measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere.</span>
<span class="attribution"><span class="source">Caitlin Moore</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Flux towers are limited in their measurement range (1 km or so) – but the data these towers collect helps verify the satellite estimates of how much photosynthesis is going on. With satellites and flux towers now providing records since the 1990s (and earlier in some cases), scientists are able to assess long-term trends in global photosynthesis. These can then be compared to “models” – the computer-based simulations predicting plant–environment interactions – as the researchers did in this recent study.</p>
<h2>What might the models be missing?</h2>
<p>Researchers in the latest study found that the decrease in CO₂ fertilisation was related to the availability of nutrients and water, which the computer simulations might not be accounting for properly. We know that nutrients such as nitrogen and phosphorus are <a href="https://www.nature.com/articles/s41559-018-0694-0">declining</a>) in some areas – which may be unaccounted for. Plants can also acclimate, or change how they grow, when the environment changes. </p>
<p>Just like we can spend less on groceries when food is plentiful, plants <a href="https://onlinelibrary.wiley.com/doi/10.1111/gcb.15375">invest less nitrogen</a> in photosynthesis when they are grown at high CO₂. When this happens, CO₂ fertilisation is <a href="https://doi.org/10.1093/jxb/erp096">less effective</a> than before. Because <a href="https://www.nature.com/articles/s41598-018-21172-9">some plants</a> have a stronger response than others, the response can be difficult to account for in computer simulations. </p>
<p>For many years, some people have assumed that carbon fertilisation will mitigate climate change by slowing the rate at which CO₂ is increasing in the atmosphere. Although the effect is built into the models used to predict future climates, the argument has <a href="https://www.heartland.org/news-opinion/news/i-love-carbon-dioxide-and-you-should-too?source=policybot">become</a> <a href="https://www.dailysignal.com/2017/07/24/dont-believe-hysteria-carbon-dioxide/?wpisrc=nl_energy202&wpmm=1">widely</a> <a href="https://www.thegwpf.org/content/uploads/2015/10/benefits.pdf">misinterpreted</a> by those who believe the world is overreacting to climate change. </p>
<p>But if the new study is right, and we have indeed been overestimating the amount of carbon that plants will pull from the atmosphere in the future, even our most cautious climate projections have likely been optimistic.</p><img src="https://counter.theconversation.com/content/151865/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amanda Cavanagh receives funding from Realizing Increased Photosynthetic Efficiency (RIPE), an international research project that is engineering crops to photosynthesize more efficiently to sustainably increase worldwide food productivity with support from the Bill & Melinda Gates Foundation, the Foundation for Food and Agriculture Research (FFAR), and the U.K. Foreign, Commonwealth and Development Office (FCDO)</span></em></p><p class="fine-print"><em><span>Caitlin Moore 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>If a major new study is right, then even our most cautious climate projections have likely been optimistic.Amanda Cavanagh, Lecturer, University of EssexCaitlin Moore, Research Fellow, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1506622020-11-26T19:12:08Z2020-11-26T19:12:08ZClimate change is making autumn leaves change colour earlier – here’s why<figure><img src="https://images.theconversation.com/files/371524/original/file-20201126-17-6rujb9.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C6000%2C3979&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/5IHz5WhosQE">Chris Lawton/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>As the days shorten and temperatures drop in the northern hemisphere, leaves begin to turn. We can enjoy glorious autumnal colours while the leaves are still on the trees and, later, kicking through a red, brown and gold carpet when out walking.</p>
<p>When temperatures rise again in spring, the growing season for trees resumes. Throughout the warmer months, trees take carbon dioxide from the atmosphere and store it in complex molecules, releasing oxygen as a byproduct. This, in a nutshell, is the process of photosynthesis. The more photosynthesis, the more carbon is locked away.</p>
<p>We know that carbon dioxide is a major driver of climate change, so the more that can be taken out of the atmosphere by plants, the better. With the warmer climate leading to a longer growing season, some researchers have <a href="https://www.fs.fed.us/nrs/pubs/jrnl/2014/nrs_2014_keenan_001.pdf">suggested</a> that more carbon dioxide would be absorbed by trees and other plants than in previous times. But <a href="https://science.sciencemag.org/cgi/doi/10.1126/science.abd8911">a new study</a> has turned this theory on its head and could have profound effects on how we adapt to climate change.</p>
<h2>Reaching the limit</h2>
<p>The researchers, led by Deborah Zani at the Swiss Federal Institute of Technology, studied the degree to which the timing of colour changes in autumn tree leaves was determined by the growth of the plant in the preceding spring and summer. </p>
<p>Temperature and day length were traditionally accepted as the main determinants of when leaves changed colour and fell, leading <a href="http://max2.ese.u-psud.fr/publications/Delpierre_2009_AFM.pdf">some scientists</a> to assume that warming temperatures would delay this process until later in the season. Studying deciduous European tree species, including horse chestnut, silver birch and English oak, the authors of the new study recorded how much carbon each tree absorbed per season and how that ultimately affected when the leaves fell.</p>
<p>Using data from the <a href="https://www.researchgate.net/profile/Barbara_Templ/publication/323254030_Pan_European_Phenological_database_PEP725_a_single_point_of_access_for_European_data/links/5a8bf0dba6fdcc6b1a442ef2/Pan-European-Phenological-database-PEP725-a-single-point-of-access-for-European-data.pdf">Pan European Phenology
Project</a>, which has tracked some trees for as long as 65 years, the researchers found in their long-term observational study that as the rate of photosynthesis increased, leaves changed colour and fell earlier in the year. For every 10% increase in photosynthetic activity over the spring and summer growing season, trees shed their leaves, on average, eight days earlier.</p>
<p>Climate-controlled experiments on five-year-old European beech and Japanese meadowsweet trees suggest what could be behind this unexpected result. In these trials, the trees were exposed to full sun, half shade or full shade. The results show that there is a limit to the amount of photosynthesis that a tree can carry out over a growing season. Think of it like filling a bucket with water. It can be done slowly or quickly, but once the bucket is full, there is nowhere for any more water to go.</p>
<figure class="align-center ">
<img alt="A misty forest with trees displaying autumn colours." src="https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5933%2C3959&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371502/original/file-20201126-21-1rb5f4f.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">Deciduous trees, which shed leaves in autumn, have a fixed amount of carbon they can absorb per season.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/colorful-tall-beech-trees-close-forest-1717461841">Alex Stemmer/Shutterstock</a></span>
</figcaption>
</figure>
<p>This research shows that deciduous trees can only absorb a set amount of carbon each year and once that limit is reached, no more can be absorbed. At that point, leaves begin to change colour. This limit is set by the availability of nutrients, particularly nitrogen, and the physical structure of the plant itself, particularly the inner vessels which move water and dissolved nutrients around. Nitrogen is a key nutrient which plants need in order to grow, and it’s often the amount of available nitrogen that limits total growth. This is why farmers and gardeners use nitrogen fertilisers, to overcome this limitation.</p>
<p>Together, these constraints mean that carbon uptake during the growing season is a self-regulating mechanism in <a href="https://www.pnas.org/content/111/20/7355">trees</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/31158300/">herbaceous plants</a>. Only so much carbon can be taken up.</p>
<h2>Earlier autumn colours</h2>
<p>In a world with increasing levels of <a href="https://public.wmo.int/en/media/press-release/carbon-dioxide-levels-continue-record-levels-despite-covid-19-lockdown#:%7E:text=The%20annual%20globally%20averaged%20level,per%20million%20benchmark%20in%202015.">carbon in the atmosphere</a>, these new findings imply that warmer weather and longer growing seasons will not allow temperate deciduous trees to take up more carbon dioxide. The study’s predictive model suggests that by 2100, when tree growing seasons are expected to be between 22 and 34 days longer, leaves will fall from trees between three and six days earlier than they do now.</p>
<figure class="align-center ">
<img alt="A pile of yellow and orange maple leaves with a dark red leaf in the middle." src="https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371523/original/file-20201126-21-1cmpnob.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">Get ready for this happening a little sooner in the future.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/kAc0En1s1h8">Greg Shield/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>This has significant implications for climate change modelling. If we accept that the amount of carbon taken up by deciduous trees in temperature countries like the UK will remain the same each year regardless of the growing season, carbon dioxide levels will rise more quickly than was previously expected. The only way to change this will be to increase the capacity of trees to absorb carbon. </p>
<p>Plants that aren’t limited by the amount of nitrogen available may be able to grow for longer in the warming climate. These are the trees which can take nitrogen from the air, such as <a href="https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/a-z-of-british-trees/alder/">alder</a>. But these species will still lose their leaves at roughly the same time as always, thanks to less daylight and colder temperatures.</p>
<p>But on the upside, with the prospect of some trees losing their leaves earlier and others losing them at the time they do now, there might be the prospect of prolonged autumnal colours – and more time for us to kick through the leaves.</p><img src="https://counter.theconversation.com/content/150662/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip James 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>Warmer temperatures cannot increase the amount of carbon deciduous trees absorb in each growing season, a new study suggests.Philip James, Professor of Ecology, University of SalfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1465332020-09-25T12:23:59Z2020-09-25T12:23:59ZAncient microbial life used arsenic to thrive in a world without oxygen<figure><img src="https://images.theconversation.com/files/359871/original/file-20200924-18-13kp7nk.jpg?ixlib=rb-1.1.0&rect=71%2C29%2C1374%2C727&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Purple microbial mats offer clues to how ancient life functioned. </span> <span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Billions of years ago, life on Earth was mostly just large slimy mats of microbes living in shallow water. Sometimes, these microbial communities made carbonate minerals that over many years cemented together to become <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/stromatolite">layered limestone rocks called stromatolites</a>. They are the oldest evidence of life on Earth. But the fossils don’t tell researchers the details of how they formed.</p>
<p>Today, most life is supported by oxygen. But these microbial mats existed for a billion years <a href="https://en.wikipedia.org/wiki/Great_Oxidation_Event">before oxygen was present in the atmosphere</a>. So what did life use instead? </p>
<p>Our team of <a href="https://scholar.google.com/citations?user=Ikl5sOsAAAAJ&hl=en&oi=sra">geologists</a>, <a href="https://scholar.google.com/citations?hl=en&user=dST-ijMAAAAJ">physicists</a> and <a href="https://scholar.google.com/citations?hl=en&user=Wx6rafEAAAAJ">biologists</a> had found hints in fossilized stromatolites that arsenic was the chemical of choice for ancient photosynthesis and respiration. But modern-day versions of these microbial communities still live on Earth today. Perhaps one of these used arsenic and could offer proof for our theory?</p>
<p>So we joined a surveying expedition of Chilean and Argentinian scientists to look for living stromatolites in the extreme conditions of the High Andes. In a small stream deep in the <a href="https://www.livescience.com/64752-atacama-desert.html">Atacama Desert</a>, we found a big surprise. The bottom of the channel was bright purple and made of stromatolite-building microbial mats that thrive in the complete absence of oxygen. Just as the clues we’d found in ancient fossils suggested, these mats use two different forms of arsenic to perform photosynthesis and respiration. Our discovery offers the strongest evidence yet for how the oldest life on Earth survived in a pre-oxygen world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing how arsenic can function in place of oxygen in photosynthesis and respiration." src="https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.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"></a>
<figcaption>
<span class="caption">Modern organisms make oxygen during photosynthesis and use it in respiration, but other elements, like arsenic, shown here as As, can work too.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Christophe Dupraz, Anthony Bouton, Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Turning sunlight into energy</h2>
<p>For the last 2.4 billion years, photosynthetic organisms like plants and <a href="https://ucmp.berkeley.edu/bacteria/cyanointro.html">blue-green cyanobacteria</a> have used sunlight, water and carbon dioxide to make oxygen and organic matter. In doing this, they turn energy from the Sun into energy to be used by life. Other organisms breathe in oxygen as they digest organic carbon, gaining energy for their respiration in the process.</p>
<p>Microbes in the ancient world also captured energy from sunlight, but their primitive machinery <a href="https://en.wikipedia.org/wiki/Oxygen_evolution">could not make oxygen from water</a> or use oxygen for respiration. They needed another chemical to do this.</p>
<p>From a biochemical perspective, there are only a few possible candidates: iron, sulfur, hydrogen or arsenic. A lack of evidence in the fossil record and minuscule amounts of some of these chemicals <a href="https://link.springer.com/referenceworkentry/10.1007%2F978-3-662-44185-5_1275">in the primordial soup</a> suggests neither iron, sulfur nor hydrogen would be likely candidates for the earliest form of photosynthesis. That leaves arsenic.</p>
<p>In 2014, our team found the first clue that stromatolites were produced by arsenic-assisted photosynthesis and respiration. We collected pieces of <a href="http://pilbara.mq.edu.au/wiki/Stromatolites">2.72-billion-year-old stromatolites</a> from the pre-oxygen world by drilling into an ancient reefs in <a href="https://www.abc.net.au/news/science/2017-05-10/early-life-on-land-in-3.5bn-year-old-hot-spring-in-pilbara/8497594">the Outback of Australia</a>. We then took these samples to France and cut them into thin slivers. <a href="https://www.synchrotron-soleil.fr/en/beamlines/nanoscopium">By measuring the X-rays that came off these samples when we bombarded them with photons</a>, we made a map of the chemical elements in the sample. If two kinds of arsenic are present in the map, then it is a sign that life was using arsenic for photosynthesis and respiration. In these relics of ancient life we found lots of both forms of arsenic, but not iron or sulfur.</p>
<p>This was tantalizing, but we wanted more proof: a modern analog to help prove our arsenic theory. No researchers had ever found a microbial mat community living in a place completely free of oxygen, but if we found one, it could help explain how the first stromatolites formed when our planet’s oceans and atmosphere were lacking oxygen.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Pieter Visscher using a field gear to measure the chemical make up of the purple microbial mats." src="https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=468&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=468&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=468&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Samples taken from the microbial mats had high levels of arsenic and lithium, but no oxygen.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">D’Angelo Duran</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Modern microbes, ancient analogs</h2>
<p>The Atacama Desert in Chile is the driest place on Earth, flanked by volcanoes and exposed to extremely high UV radiation. It’s not too different from how the Earth looked 3 billion years ago and not exactly supportive of life as we know it. Here – with the help of a team that spanned four continents and seven countries – we found what we were looking for. </p>
<p>Or destination was Laguna La Brava, a very salty shallow lake deep into the harsh desert. A shallow stream, fed by a volcanic groundwater spring, led into the lake. The streambed was a unique, deep purple color. The color came from a microbial mat, thriving quite happily in waters that contained unusually high amounts of arsenic, sulfur and lithium, but missing one important element – oxygen.</p>
<p>Could these slimy purple blobs offer answers to an ancient question?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A purple and brown clump of microbes sitting on a white background." src="https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A piece of the microbial mats living at the bottom of the oxygen-free stream.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We cut a piece of the mat and looked for evidence of minerals. A drop of acid made the minerals fizz – carbonates! – this microbe community was forming stromatolites. So our team went to work, camping out at the site for days at a time. </p>
<p>We measured the chemistry of the water and the mat with our field equipment during day and night, summer and winter. Not once did we find oxygen, and back in the laboratory we confirmed that sulfur and arsenic were abundant. Looking through the microscope, we saw purple photosynthetic bacteria, but oxygen-producing cyanobacteria were eerily absent. We had also collected DNA samples from the mat and found genes for arsenic metabolism. </p>
<p>In the lab, we mixed up microbes from the mat, added arsenic and exposed the mix to sunlight. Photosynthesis was happening. The microbes used both arsenic and sulfur, but preferred the arsenic. When we added a minuscule amount of organic matter, a different arsenic compound was used for respiration and preferred over sulfur.</p>
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<p>All that was left was to show that the two types of arsenic could be detected in the modern stromatolites. We went back to France, and using an X-ray emission technique made chemical maps from the Chilean samples. Every experiment we performed supported the <a href="https://doi.org/10.1038/s43247-020-00025-2">presence of a vigorous arsenic cycle</a> in the absence of oxygen in this unique modern stromatolite. This validates, beyond doubt, the idea that the fossil Australian samples that we studied in 2014 held evidence of an active arsenic cycle in deep time on our young planet. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The large lake of Laguna La Brava with active volcanoes behind at sunset." src="https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?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">Laguna La Brava is closer to the Martian environment than most places on Earth.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Answers on Earth, leads for Mars</h2>
<p>The harsh conditions of the Atacama are so similar to Martian and early Earth environments that <a href="https://www.sciencealert.com/life-rebounds-after-eternity-without-water-earth-s-driest-places-atacama-desert-microbes-mars">NASA scientists and astrobiologists turn to the Atacama</a> to answer questions about how life began on our planet, and how it might start elsewhere. The arsenic-cycling mats we discovered at Laguna La Brava offer strong clues to some of the most fundamental questions about life.</p>
<p>On board the Mars 2020 Perseverance rover that is currently hurtling through space is an instrument that can observe elements using the <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/pixl/">exact same process we used to make our element maps</a>. Perhaps it will discover that arsenic is abundant in layered rocks on Mars, suggesting that life on Mars also used arsenic. For over a billion years, it did so on Earth. Under the harshest conditions life finds a way, and it is that way <a href="https://doi.org/10.1038/s43247-020-00025-2">we are trying to understand</a>.</p><img src="https://counter.theconversation.com/content/146533/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pieter Visscher receives funding from the National Science Foundation, NASA Exobiology (USA), UBFC-ISITE program (France)</span></em></p><p class="fine-print"><em><span>Brendan Paul Burns and Kimberley L. Gallagher do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>How ancient microbes survived in a world without oxygen has been a mystery. Scientists discovered a living microbial mat that uses arsenic instead of oxygen for photosynthesis and respiration.Pieter Visscher, Professor of Marine Sciences, University of ConnecticutBrendan Paul Burns, Senior Lecturer, UNSW SydneyKimberley L. Gallagher, Adjunct Professor of Chemistry, Quinnipiac UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1417842020-07-07T19:52:07Z2020-07-07T19:52:07ZClimate explained: what the world was like the last time carbon dioxide levels were at 400ppm<figure><img src="https://images.theconversation.com/files/345916/original/file-20200706-3943-1sq2bv1.jpg?ixlib=rb-1.1.0&rect=33%2C92%2C5573%2C3640&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Gil.K/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
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<p><strong>What was the climate and sea level like at times in Earth’s history when carbon dioxide in the atmosphere was at 400ppm?</strong></p>
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<p>The last time global carbon dioxide levels were consistently at or above 400 parts per million (ppm) was around <a href="https://www.nature.com/articles/nature14145">four million years ago</a> during a geological period known as the <a href="http://www.geologypage.com/2014/05/pliocene-epoch.html">Pliocene Era</a> (between 5.3 million and 2.6 million years ago). The world was about 3°C warmer and sea levels were higher than today. </p>
<p>We know how much carbon dioxide the atmosphere contained in the past by studying ice cores from Greenland and Antarctica. As compacted snow gradually changes to ice, it traps air in bubbles that contain <a href="https://www.cambridge.org/core/journals/annals-of-glaciology/article/enclosure-of-air-during-metamorphosis-of-dry-firn-to-ice/09D9C60A8DA412D16645E6E6ABC1892F">samples of the atmosphere at the time</a>. We can sample ice cores to reconstruct past concentrations of carbon dioxide, but this record only takes us back about a million years.</p>
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Read more:
<a href="https://theconversation.com/climate-explained-what-caused-major-climate-change-in-the-past-137874">Climate explained: what caused major climate change in the past?</a>
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<p>Beyond a million years, we don’t have any direct measurements of the composition of ancient atmospheres, but we can use several methods to estimate past levels of carbon dioxide. One method uses the relationship between plant pores, known as stomata, that regulate gas exchange in and out of the plant. The density of these stomata is <a href="https://journals.sagepub.com/doi/abs/10.1177/095968369200200109">related to atmospheric carbon dioxide</a>, and fossil plants are a good indicator of concentrations in the past.</p>
<p>Another technique is to examine sediment cores from the ocean floor. The sediments build up year after year as the bodies and shells of dead plankton and other organisms rain down on the seafloor. We can use isotopes (chemically identical atoms that differ only in atomic weight) of boron taken from the shells of the dead plankton to reconstruct changes in the acidity of seawater. From this we can work out the level of carbon dioxide in the ocean. </p>
<p>The data from four-million-year-old sediments suggest that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010PA002055">carbon dioxide was at 400ppm back then</a>.</p>
<h2>Sea levels and changes in Antarctica</h2>
<p>During colder periods in Earth’s history, ice caps and glaciers grow and sea levels drop. In the recent geological past, during the most recent ice age about 20,000 years ago, sea levels were at least <a href="https://science.sciencemag.org/content/292/5517/679.abstract">120 metres lower</a> than they are today.</p>
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<img alt="" src="https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.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">
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<span class="caption">Recent research shows that west Antarctica is now melting.</span>
<span class="attribution"><span class="source">Elaine Hood/NSF</span></span>
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<p>Sea-level changes are calculated from changes in isotopes of oxygen in the shells of marine organisms. For the Pliocene Era, <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004PA001071">research</a> shows the sea-level change between cooler and warmer periods was around 30-40 metres and sea level was higher than today. Also during the Pliocene, we know the West Antarctic Ice Sheet was <a href="https://www.nature.com/articles/nature07867">significantly smaller</a> and global average temperatures were about 3°C warmer than today. Summer temperatures in high northern latitudes were up to 14°C warmer. </p>
<p>This may seem like a lot but modern observations show strong <a href="https://journals.ametsoc.org/jcli/article/23/14/3888/32547">polar amplification</a> of warming: a 1°C increase at the equator may raise temperatures at the poles by 6-7°C. It is one of the reasons why Arctic sea ice is disappearing. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-carbon-dioxide-has-such-outsized-influence-on-earths-climate-123064">Climate explained: why carbon dioxide has such outsized influence on Earth's climate</a>
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<h2>Impacts in New Zealand and Australasia</h2>
<p>In the Australasian region, there was no Great Barrier Reef, but there may have been <a href="https://link.springer.com/content/pdf/10.1007/BF02537376.pdf">smaller reefs along the northeast coast of Australia</a>. For New Zealand, the partial melting of the West Antarctic Ice Sheet is probably the most critical point. </p>
<p>One of the key features of New Zealand’s current climate is that Antarctica is cut off from global circulation during the winter because of the big <a href="https://www.tandfonline.com/doi/abs/10.3402/tellusa.v54i5.12161">temperature contrast</a> between Antarctica and the Southern Ocean. When it comes back into circulation in springtime, New Zealand gets strong storms. Stormier winters and significantly warmer summers were likely in the mid-Pliocene because of a weaker polar vortex and a warmer Antarctica.</p>
<p>It will take more than a few years or decades of carbon dioxide concentrations at 400ppm to trigger a significant shrinking of the West Antarctic Ice Sheet. But recent studies show that <a href="http://nora.nerc.ac.uk/id/eprint/521027/">West Antarctica is already melting</a>. </p>
<p>Sea-level rise from a partial melting of West Antarctica could easily exceed a metre or more by 2100. In fact, if the whole of the West Antarctic melted it could <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.695.7239&rep=rep1&type=pdf">raise sea levels by about 3.5 metres</a>. Even smaller increases raise the risk of <a href="https://www.pce.parliament.nz/publications/preparing-new-zealand-for-rising-seas-certainty-and-uncertainty">flooding in low-lying cities</a> including Auckland, Christchurch and Wellington.</p><img src="https://counter.theconversation.com/content/141784/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Shulmeister receives funding from the Australian Research Council and is part of a National Science Foundation grant from the US. As well as being Professor and Head of School at the University of Canterbury in New Zealand, he is an Adjunct Professor at the University of Queensland, Australia and an associate investigator at the ARC Centre of Excellence for Australian Biodiversity and Heritage (CABAH)</span></em></p>The last time global carbon dioxide levels were around 400ppm was four million years ago. On average, the world was 3°C warmer, but in high northern latitudes, it was up to 14°C warmer than today.James Shulmeister, Professor, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.