Beavers are the unsung heroes of wildfire prevention

Beavers are the engineers of the forest. Best known for chewing down trees to build up dams, the animals change their surroundings in obvious ways: pointy stumps lie in their wake; piles of branches and mud peak over riverbeds. However, scientists are increasingly noticing another, less evident way they shift their environment: wildfire prevention.

In a study from earlier this year, researchers found that areas around beaver habitat were significantly less impacted by wildfires. Specifically, they looked at data from three Rocky Mountain megafires in the United States from 2020, and found that areas with beaver dams “had significantly reduced burn severity compared to riverscapes without beaver dams or to areas outside the river corridor.” 

The same pattern has been found in Canada, explained Emily Fairfax, assistant professor of geography at the University of Minnesota, who led the study. In new research, which is not yet published, they analyzed beaver habitats in wildfire areas in British Columbia and Ontario. Beaver habitat is spread throughout much of Canada’s lakes and streams. 

“We have found very similar results in the Canadian context, which isn't surprising,” she explained. “Beavers don't just roll up to the border and be like, ‘oh, better change my whole MO.’”

Megafires, defined as blazes of 100,000 acres or more, are becoming more common due to climate change. Canada had its most devastating fire season in 2023, with 6,000 fires burning 15 million hectares of land: an area larger than the entirety of England. In Quebec specifically, an international collaboration of scientists found that the province’s wildfires were made at least two times more likely due to extreme weather conditions fuelled by climate change.

It makes the role of beavers as firefighters increasingly relevant, explained Fairfax. Along with building wetlands, beavers also create conditions that resist fire through tree cutting: they bite down trees, which thins the forest, thereby removing fuel. 

The wildfire resistance consistent with beaver habitat is due to the way they build and maintain their dams. A family of beavers builds up to 15 dams, with one primary dam creating a large pond that they live in. They dig channels between the pools, which Fairfax describes as “little water highways” which makes “it easier for them to get around, move building material, but critically, it's also spreading water out.”

“These are like irrigation lines running across valley bottoms. So instead of these little localized wet patches around a river, the whole valley is wet,” she explained.

To analyze the megafires in the western United States, Fairfax and her co-authors used satellite data to look at landscapes before, during and after a fire and then compared the images with about 1,500 beaver dam locations. That study built on previous research from 2020, which found that river corridors with beavers are about three times more fire resistant than those without. 

The new study found that during the megafires, 89 per cent of area that was beaver habitat was fire refugia, a zone within a fire that does not burn at all or burns with low intensity. In refugia, beaver habitat is protected as well as mature trees, reeds, and other plants.

The 11 per cent within beaver habitat that was burned was either on the perimeter of beaver habitat, or was new habitat that the beavers hadn't really had time to change in a big enough way to store water, Fairfax said.

River areas without beaver habitat had 60 per cent fire refugia and areas without rivers had only 40 per cent.

Where there are beavers, fires don’t spell a complete ecological wipeout, Fairfax said. That creates a zone where other animals can also survive — not just beavers and plants.

“We also see a lot of other animals really like these patches we found: moose, otter, bobcats, fountain, lions, bears, beavers, a lot of fish and frogs and turtles and snakes. Like everyone goes to these patches because it's the food in the water that's left after the fire.”

How beaver habitat resists wildfires fits into a broader picture of beavers resisting climate change impacts: they’ve also been shown to reduce the severity of droughts and floods. 

A study from this year in England by the University of Exeter and Devon Wildlife Trust analyzing a 10 year period following beavers being reintroduced to the East Devon area found “that together the wetlands were storing more than 24 million litres of water…equivalent to around 10 Olympic-sized swimming pools of water being held behind the beavers’ dams.” The researchers also found that beaver habitat reduces flooding during major rain storms.

The takeaway from the research is that protecting existing beaver habitat should be prioritized due to worsening wildfire impacts fueled by climate change, Fairfax said. 

“I think that the beavers are probably playing a disproportionately important role today because of our history of removing wetland landscapes and their ability to create them.”