Beavers March North Into Arctic: 'Tundra Be Dammed'

Beavers are marching north into the Arctic tundra, colonizing parts of Alaska and Canada and significantly altering the landscape.

The report, Beaver Engineering: Tracking a New Disturbance in the Arctic, is part of the Arctic Report Card 2021, published by the National Oceanic and Atmospheric Administration (NOAA). In it, scientists used satellite images to plot how beavers have entered the Arctic and taken over large areas.

Their findings showed that in western Alaska, there are now over 12,000 beaver ponds. This is twice the number seen 20 years ago. Between 1949 and 1955 there were no beaver ponds in this region. In Canada, efforts are now underway to map beaver ponds to establish how much their presence has increased.

The beaver colonization is of concern because of the huge impact the species has on landscapes.

In the 20th century, beavers were almost hunted to extinction after demand for their fur skyrocketed. Changes in fashion, however, saved them and there are now millions across the North American continent.

As engineers of the landscape, they are known to help prevent climate change. However, their relationship with global warming is complicated and in some places —including the Arctic tundra—their presence can increase greenhouse gas emissions considerably.

By building ponds on the tundra, beavers increase the amount of surface water—a change that causes permafrost, which is permanently frozen ground, to thaw. As this happens, organic material trapped away for thousands of years begins to break down, releasing methane and carbon dioxide in the process.

"We showed that new beavers are controlling surface water increases, which affects underlying permafrost," the report said. "Fieldwork is underway to characterize the impacts of beaver ponds on aquatic and terrestrial Arctic ecosystems, starting with hydrology and permafrost, and continuing downstream to methane flux, fish populations, and aquatic food webs. As a result of these efforts, most of the questions surrounding beaver engineering in the Arctic are presently being examined but are unanswered."

Impact on the Local Environment

Report co-author Helen Wheeler, from the U.K.'s Anglia Ruskin University, is part of the team now mapping beaver ponds in Canada. She is working to establish what impact beavers are having on the local environment and people living on the Canadian Arctic tundra.

In an email to Newsweek, Wheeler said beavers are now found as far north as Paulatuk. She said the biggest concerns about their presence are their impacts on permafrost and the release of greenhouse gasses, as well as locally on how they will alter the ecosystem for people living in the region.

"There are concerns that beavers will impact fish populations for example, but as well as the dams created by beavers changing hydrologies and impacting fish directly there is also the issue of access to important fishing and hunting grounds, beaver dams can block passage of rivers by boats, and submerged beaver dams can make travel dangerous."

In a statement, she said: "The true impact of the spread of beavers into the Arctic on the environment and the Indigenous communities who live there, is not yet fully known. However, we do know that that people are concerned about the impact beaver dams are having on water quality, the numbers of fish downstream of the dams, and access for their boats.

"The abundance of vegetation, particularly trees and woody shrubs, appears to help beavers to thrive in previously inhospitable terrain, and we are also finding beaver lodges at ever higher elevations, including above the treeline.

"Whether their expansion northwards is entirely due to climate change or increased populations following historical reductions in the trapping of beavers for fur and food, or a combination of the two, is not entirely clear, but we do know that beavers are having a significant impact on the ecosystems they are colonizing."

This article has been updated to include quotes from Helen Wheeler.

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A file photo of a beaver. There are now over 12,000 beaver ponds in western Alaska—double the number recorded 20 years ago. Getty Images