They may be cute and cuddly, but the humble beaver is dragging Earth deeper into the climate crisis, according to research.
The furry critters have invaded the Arctic, and their dams are contributing to the rapid loss of permafrost in the region, a study found.
Experts fear that greenhouse gases trapped in the ice are being released as it melts, adding to those pumped into the atmosphere by human activities.
Researchers from the US and Germany made the shock finding while studying satellite images of northwestern Alaska.
They showed that warming temperatures in the region have resulted in a boom in the local beaver population over the past 20 years.
That’s because the once-barren and inhospitable region is now teeming with trees and other shrubbery used by beavers for food and to build dams.
They appear to be building these dams in areas already susceptible to permafrost thaw, with grave consequences for the environment.
“We knew that the beavers there had spread substantially,” said study author Dr. Ingmar Nitze from the Alfred Wegener Institute in Germany.
“The lakes, which used to freeze solid, now offer beaver-friendlier conditions, thanks to their thinner seasonal winter ice cover. Lastly, the rodents aren’t hunted as intensively as in the past.
“As a result, it’s a good time to be a beaver in the Arctic. But we never would have dreamt they would seize the opportunity so intensively.”
The study found that the number of beaver dams in a 38-mile area near the town of Kotzebue has risen from from just two in 2002 to 98 in 2019.
The area of surface water in the region – a sign of melting permafrost – rose by eight per cent in that time, two thirds of which was attributed to beavers.
In a second study area, which covered 170 miles on Alaska’s Baldwin Peninsula, the number of dams jumped from 94 in 2010 to 409 in 2019.
“We’re seeing exponential growth there. The number of these structures doubles roughly every four years,” Dr. Nitze said.
Many beaver dams were spotted in the Arctic where they’d never been seen before, warping the local landscape.
Dams create lakes which overflow with water, spawning reservoirs of heat that melt the surrounding permafrost.
Permafrost in the Arctic contains huge stores of ancient methane, carbon dioxide and other greenhouse gases.
Once released into the atmosphere, these gases accelerate global warming, causing further permafrost melting in a vicious cycle.
The researchers reckon similar beaver booms are swamping in other Arctic regions.
“The growth in Canada, for example, is most likely even more extreme,” Dr. Nitze said.
“Anyone who wants to predict the future of the permafrost should be sure to keep the beaver in mind.”
The research was published in the journal Environmental Research Letters.