How a surprising twist on rewilding could help settle our carbon debt

In the Țarcu mountains of Romania, a pioneering experiment is changing the atmosphere around rewilding. Starting in 2014, around 100 European bison were gradually reintroduced to the area, having been wiped out by hunting more than 200 years ago. They now number more than 170 and graze over some 48 square kilometres. That is a success story in itself. But there is more to this project than just bringing back the big beasts. Their domain has also become a carbon hoover, sucking an estimated 200,000 tonnes of carbon dioxide out of the air every year, equivalent to taking 43,000 petrol cars off the road.

The bison themselves aren’t a significant carbon sink. It is their influence on the wider environment – compacting soil, dispersing seeds and creating varied habitats through their browsing – that has turbocharged its ability to absorb carbon. The area in which they roam is now soaking up 10 times the amount that it was before the bison were reintroduced.

The Țarcu mountains experiment is the first test of a concept that Oswald Schmitz, an ecologist at Yale University, claims has the potential to restore the atmosphere to an earlier state and hence help to arrest climate change. Schmitz and his collaborators argue that if similar projects were rolled out across the globe, both on land and in the sea, a significant amount of carbon would just disappear.

These researchers are now building their evidence base and honing their plans. Meanwhile, though, some climate scientists have raised concerns that attempts to put…