Beavers build dams. That much everyone knows. But a new study published in March 2026 has revealed something that scientists had long suspected but never fully quantified: those dams don't just change the landscape. They change the carbon cycle.
The Research
The study, led by Dr. Joshua Larsen of the University of Birmingham and published with partners from Wageningen University and the University of Bern, is the first to construct a complete carbon budget for a beaver-engineered wetland system. The team studied a stream corridor in northern Switzerland where beavers had been active for over a decade.
The findings were striking. Beaver-modified wetlands stored carbon at rates up to ten times higher than comparable streams without beaver activity. Over 13 years, a single beaver-engineered wetland accumulated an estimated 1,194 tonnes of carbon — equivalent to 10.1 tonnes per hectare per year. The sediment in these areas contained up to 14 times more inorganic carbon and eight times more organic carbon than surrounding forest soils.
Deadwood — created when rising water levels flood and kill standing trees — accounted for nearly half of the long-term stored carbon. These submerged trunks can persist for decades, locking carbon in place.
The Methane Question
There's a standard objection to wetland carbon accounting: wetlands produce methane, a potent greenhouse gas, which can offset carbon storage benefits. The study addressed this directly. Methane emissions from the beaver wetlands were negligible — less than 0.1% of the total carbon budget. The carbon sink benefits substantially outweigh any methane-related warming effects.
"Beavers fundamentally shift how carbon moves through stream systems," said Dr. Larsen. "By slowing water, trapping sediments, and expanding wetlands, they turn streams into powerful carbon sinks."
Implications for Rewilding
Beavers have been returning to Europe after centuries of near-extinction from hunting. They were reintroduced to Scotland in 2009, Wales declared them a native species in 2023, and populations are now expanding naturally across Germany, the Netherlands, and other countries where they had been absent for generations.
Beyond carbon, beaver-engineered wetlands reduce downstream flooding, filter pollutants, raise water tables during droughts, and create habitat for hundreds of other species. The University of Birmingham study adds climate mitigation to this list — and quantifies it for the first time. Rewilding beavers, the researchers conclude, could offer a major benefit for nature-based climate solutions across Europe at negligible cost.
Sources: University of Birmingham, March 18, 2026; Wageningen University; EurekAlert; Technology Networks; Peer EU; Birmingham.ac.uk
