Study finds that a herd of bison could help store the CO2 equivalent of 40K cars — here's how

A horned, brown European bison photographed against a snowy backdrop in Ukraine, with a tree branch in the forefront.

A carbon sink is anything that absorbs more carbon from the atmosphere than it releases. The world’s soil, oceans, and forests are the biggest known carbon sinks, and scientists have long acknowledged the role that they play in slowing the effects of climate change. 

But a new study shows how instrumental animals could be in tamping down on carbon emissions, too. It found that a single herd of bison has the potential to store 54 thousand tons of carbon a year.

Lead author Oswald Schmitz, Oastler Professor of Population and Community Ecology at the Yale School of Environment, studied a herd of bison in Romania’s Țarcu mountains and explained how this phenomenon occurs. 

“Bison influence grassland and forest ecosystems by grazing grasslands evenly, recycling nutrients to fertilize the soil and all of its life, dispersing seeds to enrich the ecosystem, and compacting the soil to prevent stored carbon from being released,” Schmitz told the Guardian.

“These creatures evolved for millions of years with grassland and forest ecosystems, and their removal, especially where grasslands have been plowed up, has led to the release of vast amounts of carbon. Restoring these ecosystems can bring back balance, and ‘rewilded’ bison are some of the climate heroes that can help achieve this.”

The study, backed by the Global Rewilding Alliance, calculated that a herd of 170 European bison — roaming on 30 square miles of grasslands — captured the yearly equivalent of carbon dioxide emissions from 43,000 US cars. 

Schmitz believes his research, which currently awaits peer review, could be revolutionary for the future of environmentalism and animal conservation alike. 

“Wildlife species, throughout their interaction with the environment, are the missing link between biodiversity and climate,” Schmitz explained in an interview with Yale. “This interaction means rewilding can be among the best nature-based climate solutions available to humankind.”

Dr. Alexander Lees, lecturer and conservation biodiversity reader at Manchester Metropolitan University, welcomes further research on the topic. 

“[Schmitz’s study] makes a convincing case for European bison reintroduction as a nature-based climate solution – one with major biodiversity conservation co-benefits,” he told The Guardian. 

“This study reinforces an emerging consensus that large mammals have very important roles in the carbon cycle,” Lees said. “Rewilding efforts, including, where appropriate, reintroductions, represent key tools in tackling the intertwined biodiversity and climate crises.”

A herd of European bison graze and rest in the grasslands of a wildlife refuge.
A herd of European bison graze and rest in the grasslands of a wildlife refuge. Image via Michal Köpping / Wikimedia Commons (CC BY-SA 4.0 DEED)

Beyond bison, Schmitz and his team studied a total of nine species in relation to how they impact the carbon cycle — including whales, sea otters, musk oxen, tropical forest elephants, and more. Schmitz remarked that they all had “massive potential” to capture carbon. 

“Many of them show similar promise to these bison, often doubling an ecosystem’s capacity to draw down and store carbon, and sometimes much more,” Schmitz said. 

The researchers said that the results of the study invite further research into animals around the world; they hope to carry out additional studies on high-potential species like primates, fruit bats, seals, loggerhead and green turtles, and more. 

Magnus Sylvén, the director of science policy practice at Global Rewilding Alliance, celebrated Scmitz’s research as a milestone in conservation

“Until now, nature protection and restoration has largely been treated as another challenge and cost that we need to face alongside the climate emergency,” Sylvén said. 

“This research shows we can address both challenges: we can bring back nature through rewilding and this will draw down vast amounts of carbon, helping to stabilize the global climate.”

[Editor's Note: This article was updated on May 18, 2024 after the researchers of the study reported a coding error in their original metrics. The headline and article have been corrected accordingly.

Header image via Оксана Ващук / Wikimedia Commons (CC BY-SA 4.0 DEED)

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May 15, 2024 2:13 PM
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