Beavers are expanding their range into Canada’s western Arctic, and a recent study has reconstructed when these ecosystem engineers first became active in the area — sometime around 2008.
Historically, North American beavers (Castor canadensis) have been associated with boreal and temperate waterways. However, they’re increasingly being observed moving northward in the Arctic tundra. This range expansion is partly aided by a warming climate and the growth of shrubs they depend on to build their dams and lodges.
When local Indigenous communities in the Inuvialuit Settlement Region in the Canadian Arctic noticed an increase in beavers, they “flagged this as an urgent issue requiring investigation,” study lead author Georgia Hole, from Durham University in the U.K., told Mongabay by email.
Beavers are known for their ability to build dams in streams and rivers, which blocks the flow of water, creating ponds. For the Inuvialuit, the impacts of busy beavers led to “creeks running dry, dams blocking access to historic established travel routes and harvesting sites, and changes in vegetation,” said Hole, who carried out the work while at Anglia Ruskin University, U.K.
However, in the absence of long-term scientific monitoring, nobody knew exactly when the beavers had moved in and colonized this remote Canadian Arctic region.
When beavers chew through woody plants such as trees or shrubs, their browsing leaves behind scars in the stems’ growth rings. So, to peek back in time, the researchers examined growth rings in the stems of willow and alder shrubs — local species the beavers fell — and found they record “the moment a beaver appeared and started cutting them,” Hole said.
Researchers also looked at surface water levels in satellite images over time, and found that these time stamps coincided with an increase in flooding, possibly due to the beavers’ damming activity.
Hole said these two independent lines of evidence “tell the same story” — that beavers arrived in the Inuvialuit Settlement Region starting in 2008 and have been active in the area since. This timeline fits with the real-world experience of locals, she added.
Kevin Arey, an Indigenous environmental guardian and Imaryuk monitor who worked alongside the researchers, told the Canadian Broadcasting Corporation that the beavers are everywhere and impacting the traditional way of life in the region. “What we do for a living, our fishing, our hunting, it’s making obstructions, moving water, making the rivers act differently,” Arey said.
Researchers say beaver ponds can also speed up the warming of permafrost, a concern in areas already impacted by climate change. Tracking beaver colonization and its impacts on landscapes with the new method will help inform local communities and decision-makers.
“The Arctic is transforming faster than many people may appreciate, and I hope this methodology helps us understand one ongoing change that would go otherwise go untracked,” Hole said.
Banner image: North American beaver in the Northwest Territories, Canada. Image courtesy of Helen Wheeler/Anglia Ruskin University.
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