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Restoring the populations of just 9 species can snowball the world’s carbon capture ability


a bison stands in the snow and snow on its fur and 2 or 3 more bison in the white background
Image Credit: Unsplash / Daniel Lloyd Blunk-Fernández

For the last century, the United States has enacted heavy efforts to bring back the American Bison from the brink of extinction. Now, that bison is one of nine species scientists at the Yale School of the Environment say can dramatically increase their ecosystems’ ability to sequester carbon and keep us below the crucial 1.5°C mark.


It’s estimated that before European colonizers arrived in North America, between 30 and 50 million bison roamed the Great Plains. Even more spanned across the country from Nevada to Appalachia.


These animals were imperative to the survival of Indigenous peoples living in what is now the U.S., as they used almost every part of the bison for food, clothing, and even weapons and tools for shelter. Because of this, Europeans decimated the bison populations in an attempt to starve Native Americans. “Kill every buffalo you can! Every buffalo dead is an Indian gone,” one American colonel said in 1867.


In 1902, there were fewer than 100 bison left in the Great Plains, and because of conservation efforts over the past 100 years, the number of bison across the country jumped from under 500 to 15,000, with more in captivity. Even so, in the Department of Interior’s announcement of a new $25 million bison restoration plan, they referred to bison as “functionally extinct.”


The decimation of the bison had a domino effect of environmental catastrophe, from grassland degradation and biodiversity loss to the great Dust Bowl of the 1930s and widespread crop failure. It also drastically reduced the area’s carbon sequestration ability.


Bison now exist at only 2% of their historical population, restricted to 1% of their historical range. As the scientists at the Yale School of the Environment put it, restoring the bison’s landscape to “even a fraction” of what it once was “could add an estimated 595 megatons (Mt) of CO2 annually to prairie ecosystem storage primarily by reducing soil emissions.”


That’s more than the entire country of Indonesia emitted in 2016, contributing to about 1.5% of the world’s total emissions.


Published on March 28 in the journal Nature Climate Change, the study goes in-depth on how the protection and restoration of just nine species would be a “major step forward” in the sequestration goal outlined in the Paris Climate Agreement, enhancing the entire ecosystem’s ability to capture and store carbon. Collectively, the natural world already captures and stores 50% of human-emitted carbon. This type of worldwide conservation would enhance that number.


These nine species range across the planet, from bison in the prairie, wildebeest in the savannah, sea otters in coastal kelp forests, and grey wolves in boreal forests, to African elephants in the tropics, baleen whales in the Southern Ocean, muskox in the Arctic’s wet meadows, fish close to the shore, and tiger, black-tipped reef, and lemon sharks lurking among coral reefs.



a shark swims from an angle below the shark
Image Credit: Unsplash / Alexandre Boucey

Between now and 2100, the Paris Agreement says the world must remove and store 500 gigatons (Gt) of atmospheric CO2, largely using negative emissions tech. That’s roughly 6.5Gt of CO2 a year.


It’s an understatement to say that we’re nowhere close to capturing and storing that amount.


According to the International Energy Agency, we are storing nearly 45 Mt of CO2 a year. That’s 0.044 in gigatons. To make matters worse, that’s the amount captured and either used or stored from industrial facilities, offsetting the amount fossil fuels produce. The amount of human-emitted emissions directly captured from the air and stored is only 0.01 Mt of CO2 a year, a blade of grass in the prairie of one full gigaton.


According to the agency, we need to capture almost 60Mt of CO2 a year by 2030 to keep up with the Net Zero Emissions by 2050 Scenario. A growing body of research says that direct air capture, carbon capture, and zero-emission tech like renewables are not enough on their own.


The recent report from the Intergovernmental Panel on Climate Change (IPCC) shows a myriad of mitigation and adaptation solutions to the grim picture it paints. However, the cost of these solutions compared to the emission reduction potential doesn’t leave one optimistic about the scale at which they need to be implemented.


In the IPCC report, reducing the conversion of natural ecosystems and restoring and reforesting ecosystems both run laps around the emission reduction of carbon capture tech. In fact, simply not tearing down natural ecosystems beats the emission reduction of wind by a hair, almost on par with solar power.


The 15 scientists who coauthored the Nature study say that nature-based solutions to the climate conundrum are often overlooked, especially when they involve animals.


“Ecological science has had a long history of overlooking the role of animals as an important driver of the biogeochemistry of ecosystems,” Oswald Schmitz, a Yale ecologist and the lead author of the study told the publication, Grist.


“What we say is that we know animals can change the vegetation makeup of ecosystems, and a lot of ecosystem ecologists say vegetation is important for ecosystem function and carbon cycling, then surely the animals must be important, too.”


All in all, the authors show that through rewilding the ecosystems of those nine species, the CO2 uptake would increase by 6.41 Gt a year.


To put into perspective how powerful nature is, that’s more than the 6 billion tons in greenhouse gas emissions the U.S. emitted in 2020. According to the authors, that is 64% of the current global natural climate solutions target of 10 Gt of CO2 a year.


Using wild animal conservation explicitly to enhance carbon capture and storage is known as ‘animating the carbon cycle, the authors write. Most nature-based climate solutions focus on protecting and restoring plants like trees, mangroves, and seagrasses, as well as soil and sediment microbes in ecosystems, all of which have massive carbon storage abilities. However, the authors recognize that wild animals “can have consequential effects.”


“Instead of taking 77 years to get that 500 gigatons out, we could actually have that in 35 years,” Schmitz said. “We could do it if we really made a concerted effort to rebuild these populations.”


Most experts agree that negative emissions tech will play a sizable role in the climate fight, but as the authors of the paper show, animating the carbon cycle has additional benefits that technology doesn’t.


The paper uses the wildebeest in the African Serengeti as an example. Wildebeest here were initially decimated by diseases transmitted by domestic cattle. Restoring and protecting wildebeest populations by managing disease will increase the number of animals grazing the landscape. With fewer animals grazing, the grassy savannah has more frequent and intense wildfires. Not only is this tragic for communities living in proximity, but it releases carbon stored in the biomass across 80% of the landscape.


Efforts to restore the Serengeti wildebeest in Tanzania have reduced wildfires and the region now stores up to 4.4 Mt of CO2 more than when the wildebeest population was at an all-time low.



5 wildebeest look  with 3 in the front, one of which bends down and two stare directly at camera
Image Credit: Unsplash / Charl Durand

Cases like this exist across the planet. We depend on fish for food security, but overfishing has damaged ocean ecosystems. Replenishing populations would contribute to ocean carbon storage.


The same applies to whale populations, a recently popular candidate for this type of conservation. Whales both help the ocean capture and store carbon in their bodies. And when whales live 50 and 200 years compared to the 20.6 and 65 years of the paper’s terrestrial species, the potential from protecting generations of whales over our critical 100-year timeline is astounding.


The authors show how the key to conversation efforts for all nine species “human–nature coexistence.” Right now, the Department of Interior’s (DOI) plan to restore bison in the U.S. aims to incorporate Indigenous knowledge by putting the management and ownership of some large herds in the hands of Tribes and tribal organizations. According to the DOI announcement, co-stewardship would allow for training throughout communities.


The authors of the paper write that this level of conservation requires engaging local communities in participatory planning, decision-making, and subsequent governance. It also presents the opportunity for Indigenous communities around the world to make a living on their traditional lands.


“It’s about having people think about themselves as stewards of the land, and we ought to also compensate them for that stewardship,” Schmitz said.


Specifically referring to the bison, he added in Inside Climate News, “It’s probably not possible to bring back even 10 million bison. It takes time to build up populations of these large animals, but this study is a message that says we have complex problems and we can’t put our eggs in one basket, waiting for a high-tech CO2 removal machine. We need to work within nature tech; that’s been around for millions of years.”


Restoring bison on a small scale could be tough. “Cattle ranchers would be up in arms,” he said. But, with a carbon price of $30 per ton, “bison would be worth double or triple what a cow is worth,” and maybe cattle ranches could put bison on their land and become “carbon ranchers” instead, he said, effectively creating a carbon market for conservation.


According to Schmitz, this may even bring a more stable income and economy for the entire region.


As all 15 authors write in the study, mitigating climate change and the biodiversity crisis is often thought of as two different issues. What’s needed are policies that combat both simultaneously. They point out that 30 by 30 — the landmark biodiversity agreement passed at COP15, aiming to protect 30% of the world’s waters and lands by 2030— is a good example of this.


With concluding that rewilding meets U.N. climate, Convention on Biological Diversity, and Sustainable Development goals all at the same time, they leave us with this:


“There is some urgency on both fronts because we are losing populations of many animal species just as we are discovering how much they functionally impact carbon capture and storage.”


“Thus, to ignore animals leads to missed opportunities” of ecosystems “that can be enlisted to help hold climate warming to within 1.5°C.”


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