Geographers Identify Huge Sources of CO2 Buried in Soil of the Great Plains
Geographers in the U.S. have found a new factor in the carbon cycle, and—all too ominously—a new potential source of the greenhouse gas carbon dioxide (CO2). They have identified huge deposits of fossil soils, rich in organic carbon, buried beneath the Great Plains of America.
The discovery is evidence that the subterranean soils could be a rich store, or sink, for ancient atmospheric carbon. But if the soil is exposed—by erosion, or by human activities such as agriculture, deforestation or mining—this treasure trove of ancient charred vegetation, now covered by wind-blown soils, could blow back into the atmosphere and add to climate change.
Erika Marin-Spiotta, a biogeographer at the University of Wisconsin-Madison, and her colleagues report in Nature Geoscience that what is known as Brady soil—ancient buried soil—formed more than 13,500 years ago in Nebraska, Kansas and other Great Plains states.
It now lies more than six meters below the surface, and it was buried by a vast deposit of loess—wind-blown dust—about 10,000 years ago, when the glaciers began to retreat from North America.
The significance is not that it survived the end of the Ice Age and the colonisation of the Great Plains by grazing animals, but in the fact that it is there at all, at such depths. Calculations about the world stock of soil carbon have focused on the topsoil, and the role of root systems, decaying vegetation, microbes and fungi in the natural carbon cycle. Now the climate scientists who play with models of the carbon cycle will have to think again.
“There is a lot of carbon at depths where nobody is measuring,” said Dr. Marin-Spiotta. “It was assumed that there was little carbon in deeper soils. Most studies are done only in the top 30 centimeters. Our study is showing that we are grossly underestimating carbon in soils.”
The researchers have enough evidence to put together a picture of a stormy past in an almost empty continent. The tract of prairie that now contains the Brady soil was never glaciated. As the glaciers retreated from the rest of the continent, the climate warmed, the vegetation regime changed, and it became scorched by wildfire—“an incredible amount of fire” according to the report’s author.
Before the ash, charred wood and singed fibers and stalks of the prairie grasses could begin to decompose and turn back into CO2, it was covered by the accumulating loess. It now exists as a meter-thick band of dark soil far below the surface—a hidden record of bygone climate.
The researchers calculate that, altogether, there could be as much as 2.7 billion tons of potentially reactive carbon below the Great Plains. And what happened in the Plains, could have happened in many other parts of the world. The implication is that such deposits could exist anywhere, and could just as easily be a potential contributor to global warming if disturbed.
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They are among the largest trees in the world, descendants of forests where dinosaurs roamed.
Pixabay / Simi Luft<p><span>Until recently, measuring these trees meant scaling their 80 meter high trunks with a tape measure. Now, a team of scientists from University College London and the University of Maryland uses advanced laser scanning, to create 3D maps and calculate the total mass.</span></p><p>The results are striking: suggesting the trees <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">may be as much as 30% larger than earlier measurements suggested.</a> Part of that could be due to the additional trunks the Redwoods can grow as they age, <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">a process known as reiteration</a>.</p>
New 3D measurements of large redwood trees for biomass and structure. Nature / UCL<p>Measuring the trees more accurately is important because carbon capture will probably play a key role in the battle against climate change. Forest <a href="https://www.wri.org/blog/2020/09/carbon-sequestration-natural-forest-regrowth" target="_blank">growth could absorb billions of tons</a> of carbon dioxide from the atmosphere each year.</p><p>"The importance of big trees is widely-recognised in terms of carbon storage, demographics and impact on their surrounding ecosystems," the authors wrote<a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank"> in the journal Nature</a>. "Unfortunately the importance of big trees is in direct proportion to the difficulty of measuring them."</p><p>Redwoods are so long lived because of their ability to <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">cope with climate change, resist disease and even survive fire damage</a>, the scientists say. Almost a fifth of their volume may be bark, which helps protect them.</p>
Carbon Capture Champions<p><span>Earlier research by scientists at Humboldt University and the University of Washington found that </span><a href="https://www.sciencedirect.com/science/article/pii/S0378112716302584" target="_blank" rel="noopener noreferrer">Redwood forests store almost 2,600 tonnes of carbon per hectare</a><span>, their bark alone containing more carbon than any other neighboring species.</span></p><p>While the importance of trees in fighting climate change is widely accepted, not all species enjoy the same protection as California's coastal Redwoods. In 2019 the world lost the equivalent of <a href="https://www.worldwildlife.org/threats/deforestation-and-forest-degradation" target="_blank" rel="noopener noreferrer">30 soccer fields of forest cover every minute</a>, due to agricultural expansion, logging and fires, according to The Worldwide Fund for Nature (WWF).</p>
Pixabay<p>Although <a href="https://c402277.ssl.cf1.rackcdn.com/publications/1420/files/original/Deforestation_fronts_-_drivers_and_responses_in_a_changing_world_-_full_report_%281%29.pdf?1610810475" target="_blank" rel="noopener noreferrer">the rate of loss is reported to have slowed in recent years</a>, reforesting the world to help stem climate change is a massive task.</p><p><span>That's why the World Economic Forum launched the Trillion Trees Challenge (</span><a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a><span>) and is engaging organizations and individuals across the globe through its </span><a href="https://uplink.weforum.org/uplink/s/uplink-issue/a002o00000vOf09AAC/trillion-trees" target="_blank" rel="noopener noreferrer">Uplink innovation crowdsourcing platform</a><span> to support the project.</span></p><p>That's backed up by research led by ETH Zurich/Crowther Lab showing there's potential to restore tree coverage across 2.2 billion acres of degraded land.</p><p>"Forests are critical to the health of the planet," according to <a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a>. "They sequester carbon, regulate global temperatures and freshwater flows, recharge groundwater, anchor fertile soil and act as flood barriers."</p><p><em data-redactor-tag="em" data-verified="redactor">Reposted with permission from the </em><span><em data-redactor-tag="em" data-verified="redactor"><a href="https://www.weforum.org/agenda/2021/03/redwoods-store-more-co2-and-are-more-enormous-than-we-thought/" target="_blank">World Economic Forum</a>.</em></span></p>
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