“Beavers effectively write their history into the landscape with each shrub they cut and every pond they create by damming streams" - Dr Georgia Hole.

Researchers track the northward expansion of the species. 

North American beavers are having a considerable impact on the tundra landscape as they expand into the Canadian Arctic, according to new research.

Researchers at Anglia Ruskin University (ARU) led a study investigating the northward expansion of beavers, a move thought to be driven by climate change, and found they are leaving behind a ‘significant and abrupt’ environmental footprint.

The researchers used dendrochronology (the study of tree rings) to analyse shrubs like the Salix (willow) and Alnus (alder), which have become more abundant in the region with rising temperatures. 

They found that as beavers chew through these plants, they leave behind permanent scars in the growth rings. Furthermore, the resulting beaver dams create hydrological changes that are detectable from space.

Senior author Dr Helen Wheeler, Associate Professor of Ecology at ARU, said: “The engineering activities of beavers leave a clear trail of evidence, and our findings confirm important aspects of beaver occupancy at locations extending northwards as far as the shores of the Arctic Ocean.

“Arctic Indigenous communities are already observing rapid environmental change, and beaver range expansion is part of that shift. Their impacts on lakes, rivers, fish populations and traditional practices make understanding these dynamics a priority for the Inuvialuit community.

In the study, the team recorded 60 beaver lodges or dam sites and collected Salix and Alnus stems containing scars from beaver browsing. They cross-dated the samples against regional shrub-ring chronologies spanning 1973–2023 (Salix) and 1968–2023 (Alnus), providing evidence of beaver colonisation in the region starting in 2008.

Satellite analysis revealed that at one large lodge-dam complex, beaver activity caused a significant expansion of surface water between 2015 and 2019. This flooding matched a period of intense browsing recorded in the shrub samples, providing strong agreement between two independent methods.

Lead author Dr Georgia Hole, who carried out the work while at ARU and is now based at Durham University, said: “In the Arctic, we often lack the historical baselines needed to understand ecological change. This study shows how we’ve developed an approach to reconstruct that missing history.

“Beavers effectively write their history into the landscape with each shrub they cut and every pond they create by damming streams. By dating browsing scars in willow and alder using dendrochronological techniques, and linking these to hydrological changes detected in satellite imagery, we’re able to pinpoint when and where beavers were present.

“Our findings demonstrate a powerful new way to track past beaver colonisation in Arctic regions that are rapidly transforming under climate change.”

The study was conducted as part of the BARIN project funded by CINUK, the Canada-Inuit Nunangat-United Kingdom Arctic Research Programme.

Image (C) Frank Fichtmueller/Shutterstock.com