Free-roaming bison herds deliver positive climate impact

May 17, 2024

A new study has calculated that the European bison population currently roaming free in the Southern Carpathians rewilding landscape in Romania could help to draw down and store 54,000 tonnes of carbon a year – the equivalent of the annual CO2 emissions of almost 123.000 european cars. This positive climate impact magnifies the importance of supporting wildlife comeback across European landscapes, with rewilding playing a key role.

Remarkable climate impact

Between 2014 and 2023, Rewilding Europe and WWF Romania translocated more than 99 European bison to the Țarcu Mountains – a part of the Southern Carpathians rewilding landscape where wild bison had disappeared for at least 250 years. Based on a genetic study carried out in 2022, the current population of bison is estimated at around 180 individuals. The ever-increasing range of this thriving population is now estimated to be around 300 square kilometres.

Remarkably, a new study (add link) carried out by Yale University has revealed that the current population of free-roaming European bison in the Southern Carpathians could help to draw down and store more than 54,000 tons of atmospheric carbon every year, thereby mitigating the climate impact of greenhouse gas emissions. This equates to the amount of CO2 released annually by almost 123,000 european cars.

“As a keystones species, we already know that the European bison benefits nature in many ways, while the recovery of bison populations can support the growth of nature-based tourism,” says Rewilding Europe’s Executive Director Frans Schepers. “But the results of this study magnify the importance of bringing back wildlife, including more bison, into European landscapes, which can have a climate positive, as well as a nature and people positive impact. Wildlife is the unsung hero in mitigating climate change and rewilding can play a key role supporting wildlife comeback.”


Bison interactions in the landscape

Through their grazing, browsing, and other interactions with the landscape, the European bison in the Southern Carpathians help to maintain a biodiversity-rich mosaic of forests, scrub, and grasslands, as well as numerous micro-habitats, which host a wide range of plant and animal species. These interactions promote the capture of atmospheric carbon in both vegetation and the soil, with carbon also stored in the bodies of the bison themselves. This is a process that takes time, and which may not be measurable in the first few years after bison are reintroduced, highlighting the need for long-term rewilding efforts. Studies focused on the reintroduction of other wildlife species, including American bison, have shown that measurable, positive impact in terms of carbon capture is detectable within five to 10 years of releases taking place.

Evidence from GPS collars fitted to the bison show they prefer open habitats, including grasslands, grassland close to forest edges, and forest gaps, where they can feed on fast-growing, highly nutritious plant species. The fact that the bison in the Southern Carpathians receive no supplementary feeding, as is the case with a number of other free-roaming European bison populations, means the ecological context for studying their impact on the landscape is entirely natural.

The new study, which was carried out by Oswald J. Schmitz (Yale University), Matteo Rizzuto (Yale University), and Gabriele Retez (WWF-Romania and Humboldt University) – with support from Rewilding Europe, the Global Rewilding Alliance, and WWF-Netherlands – focused on an area of grassland habitat and open-canopy forest gaps in the landscape, based on the assumption that most of the carbon impact of the free-roaming bison is concentrated there.


Ten times more carbon capture

The researchers employed a new computer model developed by the Yale School of the Environment, in collaboration with the Global Rewilding Alliance, which calculates the additional amount of atmospheric CO2 that wildlife species help to capture and store in the soils through their interactions within ecosystems. Running the relevant figures through the model, the researchers found that nearly 10 times as much carbon is captured and stored in plants, soil, and the bison themselves across the study area, compared to a situation where no bison are present.

Accounting for the methane emissions generated by the bison, this equates to a median value of 54,000 tonnes of additional carbon taken up and stored every year. This figure is an estimate calculated with the best available data, with field-based experiments necessary to provide more certainty. However, the research team are confident that the data used provide a reasonable approximation of the flow of carbon in the study area.


The bigger picture: animals, rewilding, and climate change 

The results of the new study show that European bison could play an influential role in promoting carbon capture to mitigate climate change. The case of bison in the Southern Carpathians is just one example of how animals – and their abundance in particular ecosystems – can have a significant impact on the capacity of that ecosystem to capture and store carbon. A growing body of research is now proving that restoring such animal populations to significant, near natural levels has the potential to massively increase the absorption and storage of atmospheric carbon. This process is called “Animating the Carbon Cycle (ACC)”.

The best way to animate the carbon cycle is rewilding. This means the immediate scaling up of rewilding – as a nature-based climate solution – is even more important if we are to minimise the risk of extreme climate-related impacts. To effectively address climate change, we not only need to protect and restore habitats such as peatlands, grasslands, forests, and seagrass meadows, but the animal populations they host as well.


Scaling up through rewilding

The model used by the study team to evaluate the carbon impact of bison in the Southern Carpathians is now being applied to several landscapes around the world with partners of the Global Rewilding Alliance.

“These first results show the huge potential of rewilding to address the challenges of climate change and biodiversity decline at the same time,” says Karl Wagner, Managing Director of the Global Rewilding Alliance. “As a means of enabling nature to recover, rewilding can restore the health and functionality of ecosystems, thereby boosting the capacity of those ecosystems to capture and store carbon. To fix our climate, we not only need to reduce carbon emissions as quickly as possible but scale up rewilding as quickly as possible too.”


Supporting wildlife comeback

Supporting wildlife comeback is one of Rewilding Europe’s core objectives. Over the last decade, across our portfolio of rewilding landscapes, we have employed a wide range of measures to create the right conditions for wildlife to recover of its own accord. These efforts have been complemented by species reintroductions and population reinforcements, and measures carried out on the ground by landscape teams to enhance human-wildlife coexistence. In 2022, Rewilding Europe launched the European Wildlife Comeback Fund as a tool to support the repopulation of landscapes with wildlife, with an emphasis on keystone species such as European bison, Eurasian lynx, and vultures. A Wildlife Comeback Report, commissioned by Rewilding Europe and published in 2022, shows that some European wildlife species are already making a comeback in Europe, but that we need to do more to support and scale up this recovery.

Funding for the comeback of European Bison in the Southern Carpathians has been provided by the European Union’s LIFE programme (LIFE Bison 2016-2021 and LIFE with Bison 2024-2029), the Dutch Postcode Lottery, Cartier for Nature, Fondation Ensemble, and other donors. If the bison population in the Southern Carpathians continues expanding at a similar rate, it is estimated that it will grow from around 180 individuals today, to between 350 and 450 individuals by 2030, although this is a ballpark figure. As the population increases, its positive climate impact will increase too.


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