In Alaska, Beavers Are Engineering a New Tundra

This story was originally published on High Country News.

Cyrus Harris hopped on a snowmobile one day in early January and went up a peninsula to break a trail for his sled dogs.

In the 1980's and 90's, the boas started appearing more frequently in northwest Alaska. The pastor traps the animals for making fur hats. He asked an elder about the area's first appearance.

Satellite images show a 5,000 percent increase in the number of beaver dams in the area. Because of how they flood their surroundings, boas are transforming the tundra.

Climate change is one of the reasons why the largest mammal in the world is moving north. Their proliferation is linked to a population rebound, as evidenced by the fact that boa trapping has stopped and the animals are thriving.

The National Oceanic and Atmospheric Administration's annual report tracks changes in the region, and recently cited a new disturbance as a new one. They are damming rivers and creating deeper, warmer ponds that open up new types of aquatic habitat.

Harris is worried that the community water treatment plant could be overwhelmed by the amount of drinking water that comes in from the lake. Water contaminated with their feces can cause infections in the bicyle, as well as the giardia parasites, which they excrete into the environment. Harris used to drink directly from the rivers on his hunting and fishing trips, but now he is reconsidering.