Beavers are turning rivers into powerful carbon sinks

Published in Communications Earth & Environment, the study is the first to measure both the carbon dioxide (CO₂) released and captured as a result of beaver activity in wetland environments. Researchers from the University of Birmingham, Wageningen University, the University of Bern, and several international collaborators conducted the work in a stream corridor in northern Switzerland, where beavers have been active for more than a decade.

The results show that wetlands shaped by beavers can store carbon at rates up to ten times higher than similar areas without their presence. Over 13 years, the site accumulated about 1,194 tonnes of carbon, which equals 10.1 tonnes of CO₂ per hectare each year.

Dr. Joshua Larsen, from the University of Birmingham and lead senior author of the study, said: "Our findings show that beavers don't just change landscapes: they fundamentally shift how CO₂ moves through them. By slowing water, trapping sediments, and expanding wetlands, they turn streams into powerful carbon sinks. This first-of-its-kind study represents an important opportunity and breakthrough for future nature-based climate solutions across Europe."

Beaver dams reshape rivers and carbon storage

Beavers are returning to rivers and natural habitats across Europe after years of conservation efforts. This comeback is revealing how strongly they influence carbon movement, especially in headwater streams, which are the small upper sections where rivers begin.

As beavers build dams, they flood nearby land, form wetlands, redirect groundwater flow, and capture both organic and inorganic materials, including CO₂. These changes significantly alter how carbon is stored and circulated in these ecosystems.

The findings suggest that expanding beaver populations in suitable wetland regions could provide substantial climate benefits by increasing the amount of carbon captured and stored, while limiting its release back into the atmosphere.

Beaver ecosystems act as long-term carbon sinks

To understand the full impact, researchers combined detailed hydrological measurements, chemical testing, sediment analysis, greenhouse gas (GHG) monitoring, and long-term modeling. This allowed them to develop the most complete carbon budget yet for a beaver-influenced landscape in Europe.

The study found that the wetland functioned as a net carbon sink, storing an average of 98.3 ± 33.4 tonnes of carbon each year. This was largely driven by the removal and retention of dissolved inorganic carbon below the surface.

Seasonal changes were also observed. During summer, when water levels dropped and more sediment was exposed, carbon dioxide (CO₂) emissions temporarily exceeded storage, turning the system into a short-term carbon source.

Across the full year, however, the buildup of sediments, plant matter, and deadwood resulted in significant net carbon storage. Methane (CH₄) emissions, often a concern in wetlands, were minimal and accounted for less than 0.1% of the total carbon budget.

Dr. Lukas Hallberg from the University of Birmingham and corresponding author of the study, said: "Within just over a decade, the system we studied had already transformed into a long-term carbon sink, far exceeding what we would expect from an unmanaged stream corridor. This highlights the enormous potential of beaver-led restorations and offers valuable insights into potential land-use planning, rewilding strategies, and climate policy."

Long-lasting carbon storage and climate benefits

Over time, carbon becomes locked in place as sediments build up and deadwood accumulates in beaver-created wetlands. The researchers found that these sediments contained up to 14 times more inorganic carbon and eight times more organic carbon than nearby forest soils. Deadwood from forests along riverbanks, streams, and wetlands (known as riparian forests) made up nearly half of the long-term stored carbon.

These carbon reserves can remain in place for decades, indicating that beaver-modified wetlands can serve as stable, long-term carbon sinks as long as the dams remain intact.

Dr. Annegret Larsen, Assistant Professor in the Soil Geography and Landscape Group at Wageningen University, said: "Our research shows that beavers are powerful agents of carbon capture and adsorption. By reshaping waterways and creating rich wetland habitats, beavers physically change how carbon is stored across landscapes."

When researchers applied their findings to all floodplain areas in Switzerland suitable for beaver recolonization, they estimated that these wetlands could offset 1.2-1.8% of the country's annual carbon emissions. Notably, this benefit would come without direct human intervention or additional cost.

The study, led by the University of Birmingham, Wageningen University, the University of Bern, and international partners, focused on a Swiss stream corridor with more than ten years of beaver activity.

As beaver populations continue to grow, further research will be essential to better understand how these animals influence ecosystems and future carbon storage on a larger scale.