The bison are back in the Carpathians, and they are quietly fighting climate change

High in the Southern Carpathian mountains of Romania, a giant that had vanished from these lands for generations has quietly returned. The European bison, the heaviest land mammal on the continent, once again grazes the meadows and forest clearings of the Tarcu Mountains. And, in one of nature's more pleasant surprises, this returning colossus is turning out to be an unexpected ally in the global fight against climate change.

The return of a giant

For a sense of just how remarkable this comeback is, consider that Romania lost its very last wild European bison more than two centuries ago, hunted out of existence across the region. The animal was gone from these mountains for around two hundred years. Then, in 2014, a determined reintroduction effort led by WWF Romania and Rewilding Europe began the slow, patient work of bringing the species home.

That effort has borne fruit in impressive fashion. The initial group of around one hundred bison released into the Tarcu Mountains has since grown to more than one hundred and seventy animals, making it one of the largest free-roaming bison populations anywhere in Europe. Experts estimate that the wider landscape could eventually support a herd of somewhere between three hundred fifty and four hundred fifty individuals, leaving plenty of room to grow.

An unexpected climate ally

The most eye-catching part of the story emerged from a scientific study published in 2024, carried out by researchers from Yale University and Memorial University of Newfoundland. Their work examined a question that few might think to ask: what effect does a herd of large grazing animals have on the amount of carbon a landscape can pull out of the atmosphere and store away safely in the ground?

The findings were striking. According to the study, the herd of roughly one hundred and seventy bison helps the landscape capture an additional fifty-four thousand tons of carbon every single year, spread across about forty-eight square kilometers of grassland. The researchers calculated that this is around ten times higher than the carbon removal potential of the very same ecosystem would be without the presence of the bison.

To put that abstract figure into more relatable terms, the scientists offered a vivid comparison. The extra carbon locked away thanks to the bison is roughly equivalent to taking at least forty-three thousand petrol-powered cars off the roads of the United States for an entire year. It is a genuinely significant climate contribution from a single, relatively modest herd of wild animals in one corner of Europe.

How a bison locks away carbon

The mechanism behind this is a fascinating example of how ecosystems work as connected systems. As the bison move across the land and graze, they fertilize the grasses with their dung and spread seeds through the landscape, both of which spur fresh plant growth. More vigorous plants, in turn, absorb more carbon dioxide from the air, pulling the greenhouse gas down and storing it within the vegetation and roots.

There is a second, more physical effect at play as well. With their enormous bulk, bison compact the soil as they walk, treading it down beneath their considerable weight. This compaction helps to keep carbon that is already stored in the ground locked firmly in place, rather than being released back into the atmosphere. In this way, the animals act as natural ecosystem engineers, reshaping the land simply by living on it.

A wilder Carpathia

The bison do not roam alone. The Carpathian mountains, which stretch across a large part of Romania, are often described as home to some of Europe's last great virgin forests. This wilderness shelters a remarkable concentration of large wildlife, including a brown bear population numbering in the thousands, the largest in the European Union, alongside substantial numbers of wolves and lynx that together represent a huge share of the continent's large carnivores.

This is precisely the philosophy behind rewilding: restoring natural processes and letting ecosystems, as far as possible, look after themselves. Bringing back a missing keystone species like the bison is not just about the animal itself, but about the ripple effects it triggers, from healthier grasslands and richer biodiversity to the carbon benefits that the recent research has now helped to quantify in hard numbers.

There are human benefits too, ones that matter greatly for the remote mountain communities nearby. The return of iconic wildlife has helped put the region on the map for a growing number of nature enthusiasts, drawn by the rare chance to see bison, bears and wolves in the wild. This kind of responsible wildlife tourism can channel much-needed income to local economies, giving people a direct, practical stake in keeping these landscapes wild and well protected.

The road ahead

None of this is a magic solution to climate change on its own, and the experts behind such projects are careful not to overstate the case. Rewilding faces real challenges, from ensuring peaceful coexistence with local communities to the patient work of long-term monitoring. Yet the Tarcu bison offer a hopeful and tangible example of how protecting and restoring nature can deliver benefits for wildlife and the climate at the same time, a reminder that sometimes the oldest solutions are the best.