World’s Soils Have Lost 133bn Tonnes of Carbon Since the Dawn of Agriculture
By Daisy Dunne
The world's soils have lost a total of 133bn tonnes of carbon since humans first started farming the land around 12,000 years ago, new research suggests. And the rate of carbon loss has increased dramatically since the start of the industrial revolution.
The study, which maps where soil carbon has been lost and gained since 10,000 BC, shows that crop production and cattle grazing have contributed almost equally to global losses.
Understanding how agriculture has altered soil carbon stocks is critical to finding ways to restore lost carbon to the ground, another scientist tells Carbon Brief, which could help to buffer the CO2 accumulating in the atmosphere.
Soil as a Carbon Sink
The top meter of the world's soils contains three times as much carbon as the entire atmosphere, making it a major carbon sink alongside forests and oceans.
Soils play a key role in the carbon cycle by soaking up carbon from dead plant matter. Plants absorb CO2 from the atmosphere through photosynthesis, and pass carbon to the ground when dead roots and leaves decompose.
But human activity, in particular agriculture, can cause carbon to be released from the soil at a faster rate than it is replaced. This net release of carbon to the atmosphere contributes to global warming.
New research, published in the Proceedings of the National Academy of Sciences, estimates the total amount of carbon that has been lost since humans first settled into agricultural life around 12,000 years ago.
The research finds that 133bn tonnes of carbon, or 8 percent of total global soil carbon stocks, may have been lost from the top two meters of the world's soil since the dawn of agriculture. This figure is known as the total "soil carbon debt."
Around two-thirds of lost carbon could have ended up in the atmosphere, while the rest may have been transported further afield before being deposited back into the soil.
And since the industrial revolution, the rate of soil carbon loss has increased, said lead author Dr. Jonathan Sanderman, a scientist at the Woods Hole Research Center in Massachusetts. He told Carbon Brief:
"Considering humans have emitted about 450bn tonnes of carbon since the industrial revolution, soil carbon losses to the atmosphere may represent 10 to 20% of this number. But it has hard to calculate exactly how much of this has ended up in the atmosphere versus how much has been transported due to erosion."
'Hotspots' for Carbon Loss
As part of the study, the researchers designed an artificially intelligent model that used an existing global soil dataset to estimate past levels of soil carbon stocks, Sanderman said.
"We used a dataset which defines 10,000 BC as a world without a human footprint. What we did was develop a model that could explain the current distribution of soil carbon across the globe as a function of climate, topography [physical features], geology and land use. Then we replaced current land use with historic reconstructions including the 'no land use' case to get predictions of soil carbon levels back in time."
To calculate an overall soil carbon debt, the researchers subtracted the amount of current global soil carbon from the amount of soil carbon predicted to have existed in the era before human agriculture. The model also allowed the researchers to estimate global soil carbon stocks at different points throughout history, including at the advent of the industrial revolution.
The results allow scientists to get a clearer picture on how 12,000 years of human agriculture have affected the world's soil stocks, said Sanderman.
"More carbon has been lost due to agriculture than has generally been recognized and a lot of this loss predated the industrial revolution. This loss isn't equally distributed across agricultural land. Some regions stand out as having lost the most carbon."
Map B below shows the regions that have experienced the most soil carbon loss, and includes the U.S. corn belt and western Europe. The red shading represents the very highest level of soil carbon loss since 10,000 BC, while blue shows the highest level of carbon gain.
Map A shows the global distribution and intensity of crop production (red) and cattle grazing (green) and map B shows regional changes to soil carbon stocks since 10,000 BC. On map B, blue represents the highest level of soil carbon gain since 10,000 BC, while red shows the highest level of carbon loss. Black shows unfarmed desert regions.
The U.S. corn belt and western Europe are likely to have experienced high levels of soil carbon loss as a result of long periods of intense crop production, said Sanderman.
However, the analysis also reveals a number of regions which have seen high levels of soil carbon loss despite having relatively little farming. These "hot spots"—including the rangelands of Argentina, southern Africa and parts of Australia—are considered to be particularly vulnerable to land degradation driven by agriculture, said Sanderman.
"Semi-arid and arid grasslands [the hotspots] are particularly vulnerable to potentially irreversible degradation if grazing intensity is too high. That's because there isn't a lot of soil carbon to start with and there can often be a complete shift in vegetation cover leading to lots of erosion."
Map A shows the distribution and intensity of crop production (red) and cattle grazing (green) across the world. Both have contributed almost equally to loss of soil carbon stocks, Sanderman said.
Repaying the Debt
Identifying how much carbon has been lost from the soil could also help scientists understand how much could be replenished, if soils were managed so that they took up more carbon from the atmosphere than they released into it.
Soil carbon management is one of a number of negative emissions technologies (NETs) that could help to remove greenhouse gases from the air. Research suggests that NETs will be key to meeting the Paris agreement, which aims to keep warming "well below" 2C above pre-industrial temperatures, while striving to limit increases to 1.5C.
In theory, soils could be managed in a way that would allow them to reabsorb all of the carbon that has been lost since the agricultural revolution. In practice, however, this is highly unlikely, Sanderman explained.
"This figure [133bn tonnes of carbon] is likely a maximum potential if we were willing to give up agriculture and completely restore natural ecosystems. That is obviously not going to happen, so the real potential—giving the constraint of needing to feed 10 billion people by 2050—is going to be a lot lower."
"Modifying large-scale agricultural practices to restore some of these lost soil carbon stocks might be a valuable strategy in our efforts to dampen climate change. If regenerative agriculture can restore some of the carbon that we have lost, then it might be a really valuable tool in our fight against climate change."
However, the study lacks clarity on how it considers peat soils, said Prof. Meine van Noordwijk, chief science advisor at the World Agroforestry Centre in Kenya, who also wasn't involved in the study.
Peat is a type of soil made up of waterlogged partially-decomposed plant material such as moss, which builds up over thousands of years in wetland environments including bogs.
Peat soils are thought to contain up to half of global soil carbon stocks, van Noordwijk explain to Carbon Brief, and so are of particular concern:
"Peat soils require and currently receive separate attention. Water management [of wetland soils] is a relevant part of agricultural use, leading to [carbon] losses, but also indicating opportunities for restoration."
Reposted with permission from our media associate Carbon Brief.
By Bill McKibben
To understand the planetary importance of this autumn's presidential election, check the calendar. Voting ends on November 3—and by a fluke of timing, on the morning of November 4 the United States is scheduled to pull out of the Paris Agreement.
President Trump announced that we would abrogate our Paris commitments during a Rose Garden speech in 2017. But under the terms of the accords, it takes three years to formalize the withdrawal. So on Election Day it won't be just Americans watching: The people of the world will see whether the country that has poured more carbon into the atmosphere than any other over the course of history will become the only country that refuses to cooperate in the one international effort to do something about the climate crisis.
EcoWatch Daily Newsletter
By Oliver Milman
The climate crisis is set to be a significant factor in a U.S. presidential election for the first time, with new polling showing a clear majority of American voters want decisive action to deal with the threats posed by global heating.
Do you support or oppose each of the following policies as part of the recovery from the coronavirus pandemic?<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQzODcyMC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxNjg4MzY4OX0.B-bt9mltOhK0MHFbzK8G3_8sBkDAeUsAWm-AhNZYoxQ/img.png?width=980" id="acd43" class="rm-shortcode" data-rm-shortcode-id="8724178274b9f96e27055f74a1bafe20" data-rm-shortcode-name="rebelmouse-image" />
America's largest national forest, Tongass National Forest in Alaska, will be opened up to logging and road construction after the Trump administration finalizes its plans to open up the forest on Friday, according to The New York Times.
Aerial view of the Tongass National Forest. Alan Wu / Flickr / CC BY-SA 2.0
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By Ruby Russell and Ajit Niranjan
Hamstrung by coronavirus lockdowns, frustrated school strikers have spent months staging digital protests against world leaders failing to act urgently on climate change.
Pandemic Stalls Protests<p>Last November, the head of the UN Environment Program was among the public and scientific figures to warn that 2020 offered a last chance to cut emissions. Then, few could have suspected this deadline would coincide with an unprecedented public health emergency.</p><p>The pandemic has <a href="https://www.dw.com/en/tough-times-ahead-for-climate-protesters-during-corona-pandemic/a-52978469" target="_blank">dealt climate activism a blow</a>. Niedeggen says that as a movement demanding that the world act on scientific advice, the school strikers took lockdown restrictions extremely seriously, halted public protests immediately and took their activism online.</p><p>On April 24, Fridays for Future organized a "digital strike," with Niedeggen hosting a that racked up close to a quarter of a million views. "We were not physically standing together, but we were all fighting together," she says.</p><p><a href="https://www.dw.com/en/climate-strikers-get-inventive-during-the-covid-19-crisis-fridays-for-future/a-53229262" target="_blank" rel="noopener noreferrer">Activists also gathered thousands of placards</a> from across Germany to lay out in front of the German Bundestag around the central slogan: "Fight every crisis."</p>
Opportunity for a New Normal<p>Last September's Global Climate Strike drew young and old protestors around the world, with organizers estimating a global turnout of 7.6 million, including an estimated 270,000 people in Berlin. Activists have adjusted this year's event to account for social distancing and different levels of coronavirus restrictions in cities taking part.</p><p>They say COVID-19 also presents opportunities.</p><p>"The pandemic shows that we can change our normal daily life, and we are very able to adjust to a situation of crisis," she says. The key question is how economies get back on their feet: "We have the possibility to build a new normal, to build a renewable world order, and an environmentally just, climate-just normal for everybody."</p><p>In July, Jeng was among 20 female Fridays for Future activists from the Global South to sign an open letter to G20 finance ministers warning that their decisions in "exclusive backrooms" over stimulus packages and corporate bailouts would "lock in development pathways for decades."</p><p>"The system is not broken, it was built to be unjust. We don't need recovery, we need a reboot," the letter reads, stressing that "black people, indigenous peoples and people of color," have been disproportionately hit by the economic, climate and coronavirus crises. </p>
Policy 'Not Quite There Yet'<p>Figures on stimulus spending do not suggest their words had much impact. The ministers were criticized for failing to relieve the debt of poorer countries, and according to <a href="https://www.energypolicytracker.org/region/g20/" target="_blank" rel="noopener noreferrer">Energy Policy Tracker</a>, G20 countries by August had pledged $169 billion (142 billion euros) to fossil fuels since the beginning of the pandemic.</p><p>Katrin Uba, associate professor of political science at Uppsala University in Sweden, is researching Fridays for Future. She says that despite the movement raising awareness and gaining access to policymakers, real policy change "is not there yet."</p><p>Still, she stresses that social movements go through waves of mobilization as public attention on their core issues ebbs and flows. And perhaps one of Fridays for Future's biggest achievements is birthing a politically active generation that will keep the fight up long after corona becomes a memory. </p><p>"We know clearly from our research that many of the people who came to the streets hadn't done any protesting before in their lives," she told DW. "And we also know that if you do one protest, you are likely to do more."</p>
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This week marks the official start of fall, but longer nights and colder days can make it harder to spend time outdoors. Luckily, there are several inspiring environmental films that can be streamed at home.
1. Kiss the Ground<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="ccc5f0c92a5603e68aec39e56b0db02a"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/K3-V1j-zMZw?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p><strong>Streaming On: Netflix</strong></p><p><strong>Premiere Date: Sept. 22</strong></p><p>Between <a href="https://www.ecowatch.com/wildfires-california-washington-oregon-photos-2647585008.html" target="_self">wildfires devastating the U.S. West Coast</a> and <a href="https://www.ecowatch.com/tropical-storm-beta-landfall-2647760268.html" target="_self">storms battering the Gulf</a>, the impacts of the <a href="https://www.ecowatch.com/climate-change/" target="_self">climate crisis</a> can feel overwhelming right now. <em><a href="https://kissthegroundmovie.com/" rel="noopener noreferrer" target="_blank">Kiss the Ground</a> </em>offers an alternative to all of the bad news by focusing on solutions.</p><p>The film, directed by Josh and Rebecca Tickell and narrated by Woody Harrelson, explains how we can heal the Earth through "regenerative agriculture," farming practices that draw carbon dioxide from the atmosphere and into soil as a way to restore soil health, which in turn boosts ecosystems and food supplies.</p><p>"<em>Kiss the Ground </em>shows how feasible it is to make these changes at a grassroots level immediately and make a truly substantive impact with low cost and easy to implement solutions," Executive Producer RJ Jain said in an email. "This is why I got involved."</p>
2. Public Trust: The Fight for America's Public Lands<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="5338f7a2931e356910026e5fd76fac56"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/jsKMTAaj_wQ?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p><strong>Streaming On: YouTube</strong></p><p><strong>Premiere Date: Sept. 25</strong></p><p>This <a href="https://www.patagonia.com/films/public-trust/" target="_blank">award-winning documentary</a> tells the stories of Indigenous activists, journalists, whistleblowers and historians working to protect America's <a href="https://www.ecowatch.com/tag/public-lands" target="_self">public lands</a>. The film focuses on three political struggles: the shrinking of <a href="https://www.ecowatch.com/tag/bears-ears" target="_self">Bears Ears</a> National Monument in Utah, the mining of Boundary Waters Wilderness in Minnesota and the opening of the <a href="https://www.ecowatch.com/tag/Arctic-National-Wildlife-Refuge" target="_self">Arctic National Wildlife Refuge</a> to fossil fuel exploration.</p><p><em>Public Trust</em> was directed by David Garrett Byars and produced by Jeremy Rubingh. Patagonia Films, Patagonia founder Yvon Chouinard and actor Robert Redford are executive producers. It will be <a href="https://www.youtube.com/watch?v=OGjnIG7puzY" rel="noopener noreferrer" target="_blank">released</a> on YouTube in time for <a href="https://www.ecowatch.com/national-public-lands-day-2640656776.html" target="_self">National Public Lands Day</a>.</p><p>"Our country is fortunate to have millions of acres of public lands, including National Parks, Monuments, Wildlife Refuges and Wilderness set aside for future generations," Redford said. "Sadly, these lands that belong to you and me are under unprecedented threats from the greed of big corporations, eager to weaken restrictions in the pursuit of profits. Many of our current politicians are also to blame. <em>Public Trust</em> tells the story of citizens who are fighting back. It's a much-needed wake-up call for all of us who want to preserve our unique and wild cultural heritage."<br><br>It will be <a href="https://www.youtube.com/watch?v=OGjnIG7puzY" target="_blank">released</a> on YouTube at 2 p.m. EDT Friday in time for <a href="https://www.ecowatch.com/national-public-lands-day-2640656776.html" target="_self">National Public Lands Day</a>.<br></p>
3. David Attenborough: A Life on Our Planet<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="156438a30836a765d7a92982545fc334"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/B_OFZvAd05Y?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p><strong>Streaming On: Netflix</strong></p><p><strong>Premiere Date: Oct. 4</strong></p><p>Beloved nature broadcaster <a href="https://www.ecowatch.com/tag/David-Attenborough" target="_self">David Attenborough</a> has spent his career introducing viewers to the wonders of our planet. In recent years, his footage of albatrosses swallowing <a href="https://www.ecowatch.com/tag/plastics" target="_self">plastic</a> in <em>Blue Planet II</em> has been credited with <a href="https://www.ecowatch.com/2018-fighting-plastic-waste-2624606566.html" target="_self">helping to ramp up</a> the global fight against plastic pollution. Now, in this <a href="https://www.wwf.org.uk/" rel="noopener noreferrer" target="_blank">World Wildlife Fund</a> (WWF)-produced <a href="https://www.attenborough.film/" rel="noopener noreferrer" target="_blank">documentary</a>, he reflects on the defining moments of his career and the devastating changes he has witnessed.</p><p><em>David Attenborough: A Life on Our Planet,</em> which was also produced by Silverback Films and directed by Alastair Fothergill, Jonnie Hughes and Keith Scholey, features an intimate conversation between Attenborough and Sir Michael Palin as the broadcaster reflects on his life and a career that took him to every continent on Earth. In addition to streaming on Netflix, the movie will be available in select theaters starting Sept. 28.</p><p>"For decades, David has brought the natural world to the homes of audiences worldwide, but there has never been a more significant moment for him to share his own story and reflections," WWF executive producer Colin Butfield said in a <a href="https://www.wwf.org.uk/updates/david-attenborough-life-our-planet" target="_blank">statement</a>. "This film coincides with a monumental year for environmental action as world leaders make critical decisions on nature and climate. It sends a powerful message from the most inspiring and celebrated naturalist of our time."</p>
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