The number of beavers in North America fell sharply throughout the 20th century, from an estimated 60 to 10 million to 6 to 12 million. The U.S. park service is now seeking to reintroduce them and the sooner, the better. The dams that beavers build, and the wetlands that are produced, sequester carbon — beavers, that is, play a small but crucial role in fighting climate change.
Hunted almost to extinction in the 19th century for their fur, beaver populations are coming back in many parts of North America and in Europe thanks to legal protections and reintroduction programs that began at the end of the 20th century.
This is indeed good news as recent research by Ellen Wohl of Colorado State University in Fort Collins reveals. Beaver dams cause rivers to overflow their banks and form what are called beaver meadows, wetlands rich in sediment and organic material, explains Wohl. Should a dam break, the meadows dry up and release the carbon as all the organic material becomes exposed to the air.
In a recently published article in a journal about geophysical research, Wohl reports the findings of her study of the total organic content in dried-up beaver meadows in 27 drainage basins in Rocky Mountain National Park. These now-abandoned beaver meadows account for 8 percent of the carbon in landscape. But, says Wohl, when the meadows were flooded, they were able to store as much as 23 percent of the carbon, showing that the disappearance of beavers has had a measurable impact on the environment.
As Joseph Wheaton of the department of watershed sciences at Utah State University in Logan explains to New Scientist, “beavers can transform systems extremely quickly and the long cascading list of feedbacks and impacts of their ecosystem engineering is extensive.”
In Scotland, Simon Jones oversaw a program to reintroduce beavers under which four families of Eurasian beavers were reintroduced on that country’s southwest coast in 2009; the program has so far been successful. Jones emphasizes that beavers play a crucial role in maintaining ecosystems:
Beavers are a keystone species: the dams they build and the ponds they create help to improve biodiversity, because they provide the conditions for many other wetland species to flourish. Beaver dams can also trap sediment, pollutants and regulate water flow at times of flood or drought.
Attempts to reintroduce beavers have been met with opposition. In Scotland, people mistakenly feared their dams would affect fish populations, even though beavers are herbivores.
Beaver dams can be “incompatible with modern farming, forestry and fishing in some places and will need removing. But as Jones notes, we can figure out ways to “mitigat[e] the problems that beavers cause and [allow] the species to co-exist with us.” For instance, water-levelling pipes can be inserted through beaver dams at places where they may be causing damage to commercial crops or tree plantations.
In another sign that the beaver is back, one was recently spotted in Devon in Britain, the first time a wild beaver has been seen in 800 years. As Wohl’s research about the carbon storage capacity that beaver dams create reveals, beavers play a crucial role in fighting against climate change that has resulted from our — not their — activities. Far from being pests, beavers play an essential role in making this planet a healthy place for all of us to live.
Photo from Thinkstock