A herd of 170 bison reintroduced to Romania’s Țarcu mountains could help sequester CO2 emissions equivalent to taking 43,000 US cars off the road for a year, according to new research.
This finding highlights how these animals can mitigate some climate crisis effects.
European bison vanished from Romania over 200 years ago, but in 2014, Rewilding Europe and WWF Romania reintroduced them to the southern Carpathian mountains. Since then, the bison population has grown to over 170, making it one of Europe’s largest free-roaming herds. The area could potentially support 350-450 bison.
The latest research, not yet peer-reviewed, utilised a model developed by scientists at the Yale School of the Environment, funded by the Global Rewilding Alliance and WWF Netherlands. This model, published and peer-reviewed in the Journal of Geophysical Research: Biogeosciences, calculates the additional atmospheric CO2 captured and stored in soils through wildlife interactions within ecosystems.
In the Țarcu mountains, the bison grazing on nearly 50 sq km of grasslands could potentially capture an additional 54,000 tonnes of carbon annually. This is nearly 9.8 times more carbon than would be captured without the bison.
However, the report notes that this figure could vary by up to 55%, making the median estimate uncertain. This carbon capture is equivalent to the annual CO2 emissions of 43,000 average US petrol cars, or 123,000 average European cars, which are more energy-efficient.
Prof Oswald Schmitz of the Yale School of the Environment in Connecticut in the US, who was the lead author of the report, said: “Bison influence grassland and forest ecosystems by grazing grasslands evenly, recycling nutrients to fertilise the soil and all of its life, dispersing seeds to enrich the ecosystem, and compacting the soil to prevent stored carbon from being released.
“These creatures evolved for millions of years with grassland and forest ecosystems, and their removal, especially where grasslands have been ploughed 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.”
Alexander Lees, a reader in biodiversity at Manchester Metropolitan University, who was not involved with the study, said it “makes a convincing case for European bison reintroduction as a nature-based climate solution – one with major biodiversity conservation co-benefits”.
Lees said more in-the-field research would help validate the models and assist understanding of how long it would take for bison benefits to accrue, adding: “This study reinforces an emerging consensus that large mammals have very important roles in the carbon cycle. Rewilding efforts, including, where appropriate, reintroductions, represent key tools in tackling the intertwined biodiversity and climate crises.”
As a keystone species, bison play a crucial role in ecosystems. Their grazing and browsing maintain a diverse landscape of forests, scrub, grasslands, and microhabitats.
In the Țarcu mountains, their reintroduction has also spurred nature-based tourism and rewilding-related businesses. Schmitz noted that the Carpathian grasslands have unique soil and climate conditions, so the impact of European bison might not be directly applicable to other regions, such as the less productive American prairies.
“This research opens up a whole new raft of options for climate policymakers around the world,” said Magnus Sylvén, the director of science policy practice at Global Rewilding Alliance. “Until now, nature protection and restoration has largely been treated as another challenge and cost that we need to face alongside the climate emergency. 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 stabilise the global climate.”
The report on Romania’s European bison is “the first of its kind”, said Sylvén, adding that the model provided “a very powerful tool at hand to give directions to wildlife reintroductions”.
Schmitz said the research team has studied nine species in detail, including tropical forest elephants, musk oxen, and sea otters, and has begun investigating other species as well.
He added: “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. This really is a policy option with massive potential.”
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