New report maps their spread into tundra region of Alaska and northern Canada
A new report has highlighted how beavers are heading further north and are having a significant impact on the landscape of northern Canada and Alaska.
The Arctic Report Card 2021 report, published this month by the US National Oceanic and Atmospheric Administration (NOAA), describes how the North American beaver (Castor canadensis) has expanded its range in recent years and is now colonising Arctic territory.
Authored by members of the Arctic Beaver Observation Network (A-BON), including Dr Helen Wheeler of Anglia Ruskin University (ARU), the report details how scientists are using satellite imagery to plot the beavers’ march into the Arctic tundra.
Over 12,000 beaver ponds have so far been mapped in western Alaska, with most areas seeing a doubling in the last 20 years. In comparison, analysis of aerial photography of coastal areas of western Alaska from between 1949-55 found no beaver ponds.
Beavers are a keystone species, capable of changing landscapes by creating new ponds and diverting the flow of rivers. As notorious ecosystem engineers they are agents of change, altering hydrology, landforms, biodiversity and biophysical processes. Ponds created by beaver dams increase surface water, which in the Arctic is causing permafrost to melt, in turn releasing the greenhouse gases methane and carbon dioxide.
In western Alaska, research has shown that beavers are the dominant factor in almost two thirds (66%) of cases where surface water has increased. These new ponds can also lead to the introduction of other new species, including fish and invertebrates.
The Arctic Report Card says that, In Canada, beaver distribution changes have also been observed both by local people and scientists. Concern over rising numbers of beavers in the Inuvialuit settlement region in the Northwest Territories in northwestern Canada was sufficient to instigate a harvesting incentive scheme in 2017. Although publications of academic studies of beavers in northern Canada have been sparse to date, there are reports of beavers north of the previously known range (Jung et al. 2016).
In Europe, Eurasian beavers (C. fiber) were widespread from the Arctic to the Mediterranean, before being substantially reduced around the twelfth century, and almost extinct by the sixteenth century. Today, the Eurasian beaver has restored a large area of its original range, and increased in numbers from around 1200 beavers a century ago to an estimated 1.5 million individuals today; beavers distribution reaches the northern coast throughout most of Europe (Halley et al. 2021).
In Asia, beaver distribution remains well south of Arctic tundra regions, though recent northward range extensions have been observed (Halley et al. 2021). In general, research on beavers in Arctic tundra regions is in its early stages. A coordinated circumarctic beaver pond mapping effort is underway, which will hopefully establish the footprint, if not the nature, of this new disturbance regime in the Arctic.
Pond mapping in Canada is now underway and Dr Wheeler is leading the Wildlife Change in the Arctic project in the Mackenzie Delta in Canada’s Northwest Territories to investigate the beavers’ impact on the local environment as well as the Indigenous people who live there.
Dr Wheeler, Senior Lecturer in Zoology at Anglia Ruskin University (ARU), 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 colonising.”
The Arctic Report Card further says, “Thawing of permafrost associated with new beaver ponds would initially release carbon and methane stored in permafrost, though the magnitude and fate of these fluxes are complex and unknown. Permafrost thaw, thermokarst, and the inception of a more dynamic lowland Arctic ecosystem suggest an exacerbation of effects due to warming air temperatures. As beavers create thermal and biological oases by the thousands, they could provide a foothold for boreal aquatic species, including fish and aquatic invertebrates. For now, however, these remain hypotheses that will spawn downstream studies involving field measurements and local knowledge to answer.”
The new report, Beaver Engineering: Tracking a New Disturbance in the Arctic, is led by Ken Tape, Research Associate Professor at University of Alaska Fairbanks, and involves academics from Wilfrid Laurier University in Canada, the University of South-Eastern Norway, and Anglia Ruskin University (ARU). (Newswise)
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