Scientists Are Relocating Nuisance Beavers to Help Salmon

On a bright day in a suburban Seattle backyard, a very confused beaver peers out of a wire trap. His crime? Flooding a creek behind a home and causing property damage, an increasingly common occurrence in the region. Confused, the rodent squints and watches as Molly Alves, a biologist with the Tulalip Tribe, slowly wades up to him, picks him up—trap and all—and loads him into the back of her white pickup.

Alves is now set to perform an environmental switcheroo: She's going to take the beaver out of the urban environment of western Washington and move him eastward to remote headwaters in the Mt. Baker-Snoqualmie National Forest. She's hoping that there, the beaver will create dams that turn the wild landscape back into a maze of wetlands that benefit wildlife from mosquitoes to brown bears, and to fish — including endangered salmon.

Alves helped launch the Tulalip Beaver Project in 2014 with the aim of using beavers to boost declining salmon numbers. Since the low-cost project began, scientists have relocated more than 200 “nuisance” beavers, as they are called, and created dozens of salmon-friendly beaver ponds. While scientists don’t have statistics on salmon population changes after beaver reintroductions, they say anecdotal evidence shows the rodents reshape the landscape in a way that’s fostering more fish. Now they’re set to expand their easily scalable work into new watersheds in western Washington, and other groups in the Pacific Northwest are picking up on their successful tactics too. “I've heard multiple people say that Washington is kind of a leader in beaver projects,” says Kodi Jo Jaspers, a Trout Unlimited employee and manager of the recently-launched Wenatchee Beaver Project on the other side of the Cascades.

The reintroductions are important because the outlook for wild salmon is dire, especially in the Pacific Northwest. About a third of salmon and steelhead populations on the West Coast have already gone extinct according to a 2007 study in Conservation Biology. Today, 14 more populations out of 131 remaining are at risk of extinction in Washington alone, according to a 2020 report produced by the governor's salmon recovery office. In the heavily populated Puget Sound area, only one of 22 different populations of chinook salmon—the largest species—has exceeded population goals set by NOAA in 2007.

These declines have led to a flurry of funding for salmon recovery projects. Many of those projects are costly and logistically complex; they include tearing down man-made dams that block fish passages, removing pollutants from contaminated waters and installing new salmon-friendly bridges over spawning grounds. The salmon recovery office estimates that only 22 percent of the funding needed for these projects has been met—after $1 billion has been pumped into salmon recovery efforts.

"There's so many restoration projects going on for salmon and they're so large scale and expensive and time consuming, and you don't always see the immediate benefits," says Alves. Beaver relocation, on the other hand, adds favorable salmon habitat “for a fraction of the cost and a fraction of the time and effort.”

Salmon need icy cold, clear water year-round, and that’s exactly what beavers provide. A 2019 study by Benjamin Dittbrenner, the executive director of Beavers Northwest, showed that each beaver relocated by the Tulalip Beaver Project created a swimming-pool sized pond of water for every 328 feet of stream. The beavers also slowed the stream down, causing more water to soak into the ground. The dams cooled downstream water by more than two degrees Celsius because the deeper water was harder for the sun to heat. And the ponds increase the amount of water available throughout the dry summer months by 20 percent because of the small reservoirs created behind the beaver dams. All of these new conditions add up to ideal habitat for salmon fry, as the baby fish are called.

In many ways, the history of the beaver and salmon in North America are intertwined. Beavers used to be far more numerous: Scientists estimate that between 60 and 400 million beavers shaped the landscape before Europeans arrived and decimated their numbers as a result of the fur trade. Between 1823 and 1841, the Hudson's Bay Company even enacted a "scorched earth" policy in the Pacific Northwest to rid the land of all beavers in an effort to deter fur-hungry Americans from encroaching on the British company’s territory. Settlers extirpated beavers from many areas in North America, and scientists estimated that just 6 to 12 million beavers existed on the continent by the 1980s.

After beavers declined, the salmon followed suit. A 2003 study published in The North American Journal of Fisheries Management found that the loss of beaver ponds in the Stillaguamish watershed in Washington was the biggest cause in the decline of habitat for salmon fry since the 1800s. Salmon eventually head out to sea where they face many other challenges such as predation, warming waters and getting caught as bycatch in other fisheries. Without the annual boost in population size from young salmon that beaver ponds enable, there simply aren’t enough fish available to allow the populations to grow.

"Salmon in the Pacific Northwest are dying the death of a thousand cuts,” says Dr. Daniel Schindler, a salmon researcher at the University of Washington. “We shouldn't expect that by throwing some beavers out there that salmon will move back to where they were 150 years ago.” Still, he’s quick to stress that “it's not a cure all. But certainly, adding beavers back to these systems is moving the needle in the right direction."

While relocating nuisance beavers has the potential to help fish, it also does have another clear benefit: it reduces conflict between the rodents and property owners. "A lot of people have never had to live with beavers,” says Alves. “They aren't familiar with their damming activity."

Homeowners sometimes see beaver ponds starting to form near their houses and worry about flooding, but this rarely happens. Instead, a more common problem is that beavers cause flooding on roads because developers installed culverts—large pipes installed under roads to let creeks pass through—during the beaver’s absence. They “swim up to an undersized culvert and basically see a dam with a hole in it,” says Alves. They build up around the hole, causing water to flood over the roadway. Beavers also cut down prized trees in homeowners’ yards. "Then they call us and say, 'we have got a beaver that is taking down all of our trees. Can you help us?’” says Alexa Whipple, project director for the Methow Beaver Project, one of the longest-running beaver-based habitat restoration projects in the state.

“If you have beavers in conflict with people and they will be killed if they're not moved, then yeah. We're gonna move them,” says Whipple. “But we're trying to create more programs for coexistence strategies.” Biologists use tools that homeowners might not be aware of to mitigate damage. For example, scientists install pond leveling devices that prevent flooding and wrap the base of trees in beaver-proof fencing.

Despite its low cost, when biologists do move beavers, the process is still complicated. The rodents are social animals that need to be close to other beavers. Biologists try to relocate families of beavers together to areas with an abundance of suitable trees and streams with the right topography to produce wetland complexes. Even when Alves thinks she’s identified a perfect site, sometimes “you put them there and then [the beavers are] gone the next day and you're left scratching your head," she says.

So far, the Tulalip Beaver Project has seen a roughly 40 percent success rate in establishing beavers at the sites of their release. Given the number of beavers released and their success rate, the Tulalip Beaver Project may have established dozens of backcountry beaver populations. “Individual beavers that get moved in are probably not the ones that are going to make a difference,” says Schindler. “If you establish populations and they start reproducing, that could change the functioning of the river ecosystems.”

Despite the success of beaver relocation programs, quantifying the projects’ impacts on salmon is tricky. Limited funding means projects don’t have the resources to count salmon numbers in the streams. Instead, biologists measure easier-to-collect data like water temperature, the number of new ponds and the size of those ponds. “Our metric of success is just whether they have impacted their environment somehow, in some way, by some structure,” says Jaspers, with the assumption that building better habitat equals more salmon.

Even though the biologists don’t have the written numbers to show it, they have witnessed direct benefits to the fish. “We've seen sites just completely transform to these massive beaver complexes of like 12, 13 dams and ponds everywhere,” says Alves. “Now there's hundreds of salmon fry swimming in these ponds."