The secret weapon to combat carbon emissions has been discovered: beaver

Beaver dams and ponds can turn stream channels into annual net carbon sinks, capturing more carbon than they release in a year, a new study finds.

The discovery has major implications for the reintroduction of the Eurasian beaver (castor fiber) across Europe, after it was hunted to the brink of extinction for centuries. If similar patterns hold elsewhere, the animals could help mitigate climate change by sequestering greenhouse gases without the need for expensive infrastructure.

“Beavers are not going to solve climate change, but our study shows that these natural engineers can quietly help river landscapes store more carbon for decades to come,” study lead author Lucas Hallberg, a researcher at the University of Birmingham in the UK, told Live Science in an email.

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Carbon balance calculation

In the study, published March 18 in the journal Communication, Earth and Environment, researchers investigated a half-mile (0.8 kilometer) stream affected by beavers in northern Switzerland.

Until the establishment of a beaver swamp in 2010, the river was heavily wooded and functioned more as a floodplain. When beavers were introduced, they cut down many trees for dams and expanded the canopy for smaller plants.

Scientists measured carbon in water that is released into the atmosphere and stored in sediment, biomass and dead trees. They did this by collecting core samples from the sediment and surrounding forest, as well as plant samples from algae growing along the river. The researchers also calculated water flow in streams to help determine water levels, salinity content, and the amount of sediment passing through the area.

The results showed that wetlands are net sinks that sequester 108 to 146 tons (98 to 133 tons) of carbon per year. This reduced amount of carbon is equivalent to between 832 and 1,129 barrels of oil consumed.

The research team estimated that the resulting wetlands could potentially offset 1.2% to 1.8% of Switzerland’s annual carbon dioxide emissions, making the entire floodplain suitable for recolonization of Swiss beavers.

The researchers were careful not to overestimate the beaver’s abilities. This is especially true because only one site was studied, and the amount of carbon stored can vary depending on factors such as climate, geology, vegetation, and the size of the room in which beavers spread out. But Hallberg argued that beavers can help make infrastructure more sustainable at low cost.

“Taking advantage of natural processes from the beginning is not only ecologically sound, but also economically prudent,” he said.

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Emily Fairfax, assistant professor in the University of Michigan’s Department of Geography, Environment and Society, who was not involved in the study, welcomed the findings. He said the study helps counter the common misconception that restoring wetlands doesn’t seem worthwhile because they can emit carbon dioxide.

“I think the way they described beaver ponds as durable carbon sinks is really important,” she told Live Science. “This is a very powerful tool to help with the wetland restoration that needs to happen, and to remove some of the skepticism about beavers…People are quick to think of beavers as a problem and look for reasons to tightly manage beavers, and I think this study does a really good job of showing that there’s no need to do anything but let beavers be beavers.”

bouncing beaver

Beavers were hunted to the brink of extinction across vast swaths of their range in both Europe and North America, taking with them carbon-rich wetlands. Now, as populations recover, researchers are beginning to understand their role in carbon sequestration.

Hallberg said it’s difficult to estimate with certainty how much carbon could be removed by large-scale beaver restoration in either North America or Europe, because suitable habitat and carbon input vary by location. But he noted that earlier research in Colorado’s Rocky Mountain National Park estimated that active beaver swamps could account for as much as 23% of the total carbon storage in the landscape.

Fairfax said that “if we were to seriously restore beavers,” the resulting increase in carbon dioxide would be “not negligible.”

He added that the new findings may even underestimate the carbon sequestered by beavers, since healthy beaver wetlands can make river landscapes more resilient to catastrophic wildfires and prevent some carbon from being released in the first place.

“The joke in beaver science is that if there’s a problem, there’s a beaver to take care of it,” she says.