A recently published study suggests that a herd of more than 170 European bison reintroduced into Romania’s Țarcu Mountains may contribute significantly to carbon sequestration—potentially offsetting the annual emissions of approximately 43,000 petrol-powered vehicles in the United States. The findings underscore the environmental value of restoring native wildlife as part of broader climate change strategies.
More than 200 years ago, the European bison, once native to Romania, got extinct from the region. In 2014, efforts by conservation organizations Rewilding Europe and WWF Romania led to the reintroduction of the species into the southern Carpathian Mountains. From an initial group of around 100, the population has now surpassed 170 individuals, making it one of the largest free-roaming bison herds on the continent. Researchers believe the Țarcu landscape could sustain as many as 350 to 450 animals in the future.
A newly developed model by scientists at the Yale School of the Environment—supported by the Global Rewilding Alliance and WWF Netherlands—estimates that the current bison population could help absorb an extra 54,000 tonnes of carbon dioxide each year. This is due to their grazing activity across nearly 50 square kilometers of grasslands. According to the model, this level of carbon capture is roughly 9.8 times higher than what would occur without the presence of bison. However, the authors caution that this figure could fluctuate by up to ±55% depending on local ecological variables.
The environmental impact is comparable to eliminating the emissions of 43,000 standard US gasoline cars annually. If the higher end of the carbon capture range is accurate, the offset could represent as many as 84,000 US vehicles or around 123,000 European cars, which typically emit less due to greater fuel efficiency.
Professor Oswald Schmitz, the lead author and a faculty member at Yale, emphasized the ecological role of bison in regulating climate processes. “Bison shape their habitats through balanced grazing, natural fertilization of the soil, seed dispersion, and compacting the earth—each of which contributes to preventing the release of stored carbon,” he said.
“These species have evolved alongside grassland and forest environments over millions of years,” Schmitz explained. “Their disappearance—and the conversion of these lands for farming—resulted in significant carbon emissions. Rewilding can restore that equilibrium, and bison are proving to be instrumental in that effort.”
Although the study has not yet undergone full peer review, the modeling approach it relies on was previously validated and published in the Journal of Geophysical Research: Biogeosciences.
Dr. Alexander Lees, a biodiversity expert at Manchester Metropolitan University who was not involved in the project, praised the research for reinforcing the growing consensus around rewilding as an effective climate strategy. “This study presents a strong case for bringing back European bison as a nature-based solution that also delivers critical biodiversity gains,” he said.
Lees also stressed the importance of conducting further on-the-ground research to confirm the theoretical benefits. “Understanding how long it takes for such ecological advantages to manifest is essential,” he noted. “But the role of large herbivores in maintaining carbon cycles is becoming increasingly clear.”
European bison contribute to ecology as an essential element. Their presence supports a rich mosaic of vegetation types—from woodlands and grasslands to shrubs and microhabitats—helping to sustain biodiversity across the landscape. In the Țarcu region, their return has also sparked growth in nature tourism and rewilding-related community ventures.
Still, Schmitz noted that these findings might not be directly applicable to other regions with different environmental conditions. For instance, North American prairies, which differ significantly in soil structure and productivity, may not experience the same benefits.
Nevertheless, the research strengthens the case for rewilding as a dual-purpose tool—fostering ecological resilience while addressing climate challenges. If nature returns, climate stability can follow.
