North America once had 400 million beavers, nearly wiped out by the 1900s; they are now helping shield wildfire-prone stream corridors in northeastern Washington from flames

Before the arrival of European settlers, around 400 million beavers were running about the continent’s waterways, quietly reshaping rivers, flooding pastures, and creating what today’s science recognizes as some of the most resilient habitats on the planet. But then came the fur trade. By 1900, the vast beaver population had been reduced from the once-huge number to just 100,000 animals, drastically altering the hydrology of the whole continent.

Marshes dried out, stream beds shrunk, and the natural fire breaks created by the beavers over centuries vanished. Today, as massive wildfires rage across the western part of the USA, experts are making a stunning discovery: the country might have accidentally destroyed its most efficient natural system of fire protection. It was on four legs, had a flat tail and an extreme tendency to build dams.

Why beavers are basically nature's firefighters


This is what you may not learn about beavers in school: these animals not only inhabit wetland areas, but also create them. When a beaver constructs a dam, it does not simply slow down a stream; it raises the water table, saturates the soil in the area, and carves out channels that channelize pond water deep into the surrounding landscape. The outcome is an extensive, wet, green corridor that remains green even when everything else around it has dried up.

According to a 2020 study titled “Smokey the Beaver: beaver-dammed riparian corridors stay green during wildfire throughout the western United States,” published in Ecological Applications, beaver-dammed riparian corridors had an average reduction in vegetation greenness of just 19%, while those that were devoid of beavers saw an average reduction of 51%. This difference is statistically significant, and evident even from space photographs. In other words, according to the study, places with beavers remained green while those without did not.

This process is virtually elegant in its simplicity. Wet leaves and water-filled soil do not ignite easily; it’s the same concept as not being able to start a campfire from soaked wood. In fact, when a wildfire is heading toward a wetland that has been beaver-built, it tends to take the easier route and bypass it.

What's happening in northeastern Washington, and why it matters

In the dry stream corridors of northeast Washington, there emerged a unique experiment of peaceful co-existence. The Methow Okanogan Beaver Project has been in operation since 2008, and this project involves live-trapping the “nuisance” beavers, the ones that had caused problems for private property owners, and moving them to degraded unoccupied stream segments on the public lands. In simple terms, the idea is to relocate the conflicting animals to places where their engineering skills can be a public asset.

Beaver wetlands in northeast Washington's dry landscapes are currently functioning as buffer zones against wildfires, according to the UMass Amherst RiverSmart Communities project. The project involves collaborative efforts of the US Forest Service, Washington Fish and Wildlife, habitat biologists, and volunteer community members; and is a significant change in the approach to the management of beavers in the American West.

The Methow Valley is well aware of the potential impact of these events since back in 2014, Carlton Complex wildfires raged and destroyed in excess of about 250,000 acres and over 300 houses, thus becoming one of the biggest wildfires in the history of Washington State. Restoration ecologist Alexa Whipple examined burned riparian areas with and without beavers’ dams in the Methow River drainage area, and found measurable differences in how riparian areas recovered post-fire.

A reckoning more than a century in the making

It could have been a happy story of conservation success and, in many ways, it is. Numbers of North American beavers have recovered from such an appalling figure of 100,000 to an estimate of 10 to 15 million now. Still, it represents only a small percentage of their original population; and the ecological deficit caused by the population collapse, which was complete by 1900, roughly 126 years ago, remains enormous.

The fur trade wasn't just about the extermination of one species but the destruction of an entire wetland system. Beaver ponds that once held back water throughout the landscape disappeared. Rivers that once flowed lazily and overflowed their banks cut deeper and swifter. Those landscapes created by that time are the same ones burning more fiercely because of global warming.

There is evidence suggesting that the beaver ponds may also filter out the ash and the pollutants carried by water to the rivers after the wildfires. It means that the advantages of the beavers’ presence do not end even after the fires are long extinguished.

The uncomfortable question no one's asking loudly enough

This is where things get serious. The scientific evidence is conclusive, the long-term experimental projects are progressing fairly, and the logic is undeniable. So then, why isn’t beaver-led restoration central to U.S. wildfire policy in the West? First and foremost, there’s bureaucracy at work. Beavers continue to be considered a nuisance species in many states. Hunting seasons continue to be open in many parts of the country. And the idea of the beaver as an environmental problem, the destroyer of trees and floods, and thus a pest to be controlled rather than an ally to be employed, has deep roots in rural communities dealing with flooding roadways and damage to property.

There are signs of change in the US Forest Service. Beaver dam analogs have been tested on several projects in New Mexico and Washington; essentially, they are artificial structures that mimic the hydrologic effect of natural dams, sometimes used to attract beavers to specific locations. However, they are only small-scale experiments at this stage, and the will to scale them up on a national level may still be lagging behind.

Meanwhile, wildfire seasons get longer. The fires get bigger. And somewhere in northeastern Washington, there is a relocated beaver quietly raising the water level and keeping vegetation alive, doing for free what no fire retardant would do.