Beavers aren’t going to save the world â€“ but they are doing their bit for carbon capture and storage. The dams they build, and the wetlands produced as a result, lock away a surprising amount of carbon.
“Beavers offer a mechanism of carbon storage,” says Ellen Wohl of Colorado State University in Fort Collins. Beaver dams cause water to breach riverbanks, creating areas of wetland known as beaver meadows, which contain large amounts of sediment and organic material. If the dam breaks the meadows dry out, exposing the material to the air and releasing some of the carbon stored within them.
Using previously published carbon-content values, Wohl estimated the total organic content from dried-up beaver meadows in 27 drainage basins in Rocky Mountain National Park, and found it accounted for 8 per cent of the carbon in the landscape. She estimated that when the meadows were flooded they may have sequestered as much as 23 per cent of the carbon.
Beaver numbers have been declining in the park since the 1940s. Wohl says there were once between 60 and 400 million beavers in North America â€“ a number that would have had a significant effect on the ecosystem. There are now thought to be 6 to 12 million, and the park service is working towards reintroduction.
“Beavers can transform systems extremely quickly and the long cascading list of feedbacks and impacts of their ecosystem engineering is extensive,” says Joseph Wheaton of the department of watershed sciences at Utah State University in Logan.
“With some subtle and cheap shifts in how we manage landscapes and rivers, allowing beavers to do a lot of the work for us can have profound impacts,” he says â€“ but ecologists will have to manage people’s expectations about just how much beavers can do.