In response to a rapidly warming Arctic region, Nature's engineers--beavers--are moving north into previously unoccupied regions of Canada and Alaska. Previously, beavers made sporadic inroads into the north, but not the migration is on a large scale. In Alaska alone, the number of beaver ponds in the tundra has doubled in the last twenty years, now numbering about 12,000. [see photo below, credit U. Alaska] More lodges are found dotted along river banks and lakeshores. Computer modeling shows that by 2100 the entire north slope will be colonized by beavers.
The tundra was once too sparse to be good habitat for Castor canadensis but warming temperatures has caused shrub expansion, which provides food and building materials for the industrious rodents. Running water also extends into shorter winters for longer periods. The downside of pond creatioin is that it creates more warming with the potential of melting permafrost, releasing methane gases stored underground. In the Noatak River basin, scientists have found a clear evidentiary link between beaver ponds and methane hotspots using aerial infrared imaging.
Canada's beaver populations have been increasing in the far north, but not as fast as in Alaska. Surveys conducted with the cooperation of Gwich'in people indicate a doubling in numbers since the 1960s. Dam building has positive bio-feedback effects too. Many other species are attracted to wetlands created by beavers forming an oasis of biodiversity. Residents of Devon, England have been pleasantly surprised by the ability of relocated beavers to keep a wetland green during severe drought that has parched surrounding fields.
Some human residents are concerned by local flooding that can block routes. Whether beavers should be again controlled by human predation is a question open to debate as their numbers continue to increase. Researchers, conservationists and natives will gather in February at the annual meeting of the Arctic Beaver Observation Network in Fairbanks to discuss the issues.