Why Are Beavers Moving Into the Arctic?

Beavers have been moving north across Alaska for decades. Scientists are still working out exactly why, and some of the latest findings are unexpected.

Before 1950, there was little evidence of beaver engineering in Arctic Alaska, but their presence grew considerably during the second half of the century. A 2022 study estimated around 12,700 beaver ponds across Alaska’s Arctic tundra. The exact current total in 2026 remains unknown.

Polar Journal has previously reported on this rapid expansion of beaver activity in Alaska. Now, a new study provides an update on what may be driving it.

What happens when beavers arrive?

Beavers are powerful “ecosystem engineers.” By building dams and digging channels, they can turn flowing streams into networks of ponds and wetlands, changing water levels, habitats and the surrounding landscape.

In the Arctic, beaver engineering has an additional important consequence: beaver ponds can accelerate permafrost thaw and affect the carbon cycle. Polar Journal previously reported on a study that found methane hotspots were 51% more common around beaver ponds than around nearby water bodies. Flooding creates waterlogged, oxygen-poor conditions where microbes can produce methane as organic matter decomposes. Permafrost thaw can also expose previously frozen carbon to decomposition.

The scale of the transformation caused by beaver engineering in Alaska is substantial. The US National Oceanic and Atmospheric Administration (NOAA) has described it as a new Arctic “disturbance”.

For people living in the region, some effects are concerning. Communities in Alaska have reported impacts on fishing, as well as water quality and boat access.

Why are beavers moving north?

Climate change has long been the main explanation for the northward expansion of beavers. A new study by researchers at the University of Alaska Fairbanks looks more closely at the specific environmental changes making this expansion possible.

The researchers analysed satellite observations of nearly 1,500 beaver ponds in northwest Arctic Alaska between 2005 and 2020. They estimate that conditions became around five times more favourable for establishing new ponds during this period, while observed beaver activity increased approximately threefold.

According to the study, several factors were associated with new pond establishment: milder winters, warmer Junes, greater vegetation productivity and higher spring river discharge. Interestingly, the same conditions did not necessarily help ponds persist. Cooler Junes and lower spring discharge were associated with a greater likelihood that existing ponds remained occupied.

Another finding challenged previous expectations. Expanding shrubs had been proposed as one reason beavers could move north, since they provide food and building material. Yet the new research found that local shrub cover was not an important predictor of new pond establishment.

The new study points towards continued beaver expansion. How quickly they will spread, how far they will go and what their growing presence will mean for Arctic ecosystems remain open questions.

Dr. Yana Kirichenko, PolarJournal