Colonization of the Beaufort Coastal Plain by Beaver (<i>Castor canadensis</i>): A Response to Shrubification of the Tundra?

Abstract

A consequence of rapid global warming has been the shrubification (increase in shrub abundance, cover, and biomass) of arctic and alpine tundra ecosystems. Shrubification is likely a key driver of predicted and observed changes in the biodiversity of the Arctic. The American Beaver (Castor canadensis) has a vast distributional range, covering most of north America below the tree line; however, it has not been recorded in tundra habitat of the Beaufort Coastal Plain of Yukon and Alaska. in 2015, we observed a beaver dam, lodge, and winter food cache on the Babbage River in Ivvavik National Park, Yukon, Canada. Local Inuvialuit hunters first observed beavers on two rivers immediately east of the Babbage River in 2008 and 2009. Together, these are the first observations of beavers on the Beaufort Coastal Plain and indicate initial attempts at colonization. Colonization of the Beaufort Coastal Plain by beavers may have been facilitated by shrubification of river valleys on the tundra of northern Yukon and adjacent Alaska, which is a consequence of rapid climate warming in the western Arctic.

Tundra be dammed: Beaver colonization of the Arctic

“…It is also possible that beaver populations are still rebounding from heavy trapping during the 19th and early 20th centuries. Recent observations suggest beaver movement from forest into tundra of western and northwestern Alaska (Brubaker et al., ; Rabung, Sam and Norton Sound Bering Straight Regional Planning Team, ), and northwestern Canada (Jung, Frandsen, Gordon, & Mossop, ), but beavers are thought to be absent from the North Slope of Alaska (Huryn & Hobbie, ). Because beavers are well known agents of disturbance and wetland formation in their contemporary distribution, it is important to understand where and how rapidly beavers will colonize the Arctic, and how this will impact riparian and freshwater ecosystems set within permafrost landscapes.…”

“…Orange line approximates treeline, which was historically considered to be the range limit of beavers (Bockstoce, ; McCulloch & Hopkins, ). Yellow arrows denote known beaver colonization routes since 1999, including an observation of a new dam on the Babbage River in Canada (Jung et al., ), and evidence of many new dams and ponds in the white box covering the western Brooks Range. White arrows speculate future colonization routes, and plus signs indicate observations of beaver ponds beyond treeline on the Seward Peninsula…”

Expanding beaver pond distribution in Arctic Alaska, 1949 to 2019

“…Exhaustive beaver pond mapping on the scale shown here has not previously been implemented in the Arctic. Scattered observations in northern Canada, as in Alaska, indicate that beaver engineering is expanding into new areas 44 , in some locations reaching the Arctic coast, though changes in pond extent and density have not been studied in most treeline and tundra regions. Given the vastness of northern Canada compared to northwest Alaska, the number of new beaver ponds could be an order of magnitude larger than 10,000 in Canada.…”

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“…With postglacial warming temperatures, vegetation on the island changed rapidly from tundra (suitable for beavers; Aleksiuk 1970; Jung et al 2016;Tape et al 2018) to forest, a spruce (Picea sp. )nonarboreal birch (Betula sp.)…”