NOTEBOOK FEATURE: California Taps Beavers to Restore Watersheds

Written by Robin Meadows

Beaver trimming a small tree limb. Photo by DOE Office of Legacy Management.

As evidence for the wide-ranging environmental benefits of beavers has mounted, champions of these 40-to-70-pound rodents have increasingly clamored for restoring them in California. Now, the state has finally joined others, including Oregon, Washington and Utah, that are putting these furry ecosystem engineers to work. This year marks the launch of a $1.44 million per year California Department of Fish and Wildlife (CDFW) program to bring beavers back to watersheds throughout their historic range in the state.

“We agree: time for California to embrace beavers,” CFDW director Chuck Bonham wrote in a January 2023 op-ed in Outdoor California.

The agency is in the process of working out the details of its new beaver restoration program. Goals include moving beavers from places where they cause harm, such as flooding on farms or roads, to places where they can do good, such as mountain watersheds. “The program funds dedicated scientists who, once hired by CDFW, will begin working on projects that help the environment by bringing beavers back to California rivers where they once thrived,” Bonham wrote.

Another goal is to “identify and support non-lethal deterrent methods to help mitigate human-beaver conflict,” CFDW staff wrote in an email. Under current regulations, the agency issues permits for killing beavers provided that “all alternatives are exhausted and beavers are continuing to damage or threaten to damage land or property.”

Environmental engineers

Beavers once lived in streams across North America, but trapping and eradication efforts cut the population from as high as 200 million to an estimated 10-15 million today. While beavers were nearly wiped out in California in the early 1900s, they rebounded following protections enacted in 1911. The state revised beaver regulations in 1930 to allow killing those that threaten private property.

Biologists reintroducing beavers in Washington state. Photo by U.S. Forest Service.

The rodents’ capacity for both nuisance flooding and environmental benefits stems from their habit of building dams across waterways. Dams create pools that encircle their lodges—dry, elevated living spaces with underwater entrances—and protect against predators. Thanks to their large lungs, beavers can stay underwater 15 minutes and swim half a mile before popping up.

Most beaver dams are on the small side but one in Alberta, Canada is half a mile long and so immense it shows up in satellite images. CDFW credits the beaver as the only species known to create its own habitat, and both the California Institute of Technology and the Massachusetts Institute of Technology chose the beaver as their mascot, with the latter lauding “its remarkable engineering and mechanical skill and its habits of industry.”

Beavers expand and even form a wealth of water-rich habitats including wetlands, riparian areas, and meadows. Their contributions to the natural world range from recharging groundwater and reconnecting streams with floodplains to providing fire breaks and refuges for species during drought.

Beaver reintroduction

California first began reintroducing beavers to the mountains a century ago.

This is the second time California has operated an official beaver reintroduction program in recognition of their ecosystem services. The first was between the early 1920s and 1950, when the state relocated more than 1,200 beavers from streams on farms to mountain watersheds to “save water for fish, wildlife and agriculture.” Getting beavers to new homes in the El Dorado National Forest entailed dropping them from airplanes in boxes outfitted with parachutes.

Today, CDFW will draw from modern beaver restoration efforts elsewhere. Utah, which established a formal beaver management program in 2010, is a leader in optimizing the species’ restoration. “We’ve been doing this for a long time but we’re still learning,” says Darren DeBloois of the Utah Division of Wildlife Resources, whose work includes coordinating the beaver management program.

Best practices honed over the years include catching and relocating entire families. Beavers are monogamous and mate for life, and young typically stay with their parents for two years to help maintain the living quarters and raise the next generation of kits.

Veterinarian radio tagging an anesthetized beaver in Utah. Photo by Utah Division of Wildlife Resources.

Utah’s program has expanded the traps used to include both live clamshell traps, which completely enclose beavers, as well as humane snares, which allow some freedom of movement. “We used to use clamshell traps exclusively but changing water levels can pose a danger to beavers,” DeBloois says. “Utah State researchers showed you can use snares that are long enough to accommodate rising and falling water levels.”

The next step is quarantining the trapped beavers on site to reduce the risk that they will carry fish pathogens like whirling disease—which causes spinal deformities in trout and salmon that make them swim in circles—to their new home. Whirling disease is spread by worms living in mud, and beavers scoop up mud when making and maintaining dams.

Radio tagged beaver coming out of anesthesia in Utah. Photo by Utah Division of Wildlife Resources.

To see if relocated beavers stay where they’re put, veterinarians fit the tails of some with radio tags. Picking the right release location makes them less likely to stray. “Beavers need willows and slow-running streams with reliable water running year round,” DeBloois says. “The streams can’t dry up in the summer.”

Demand for beavers is high. Other federal and state agencies “are really excited about it but our folks are more aware of the possible conflicts,” DeBloois says. “The biggest hurdle is that you need to make sure beavers won’t cause a problem—you need to check the release site, and what’s upstream and downstream.”

Now DeBloois and his colleagues are looking at ways of enhancing and rehabilitating potential beaver habitat. Examples include replanting willows and adding structures that mimic beaver dams. Called beaver dam analogs, the latter consist of willow branches woven through posts that are driven into the streambed.

“If you move beavers cross country, they’re more vulnerable,” DeBloois says. “If we build the dams, are they more likely to stay?”

Sierra Nevada headwaters

Julie Fair, Director of California Headwaters Conservation for the nonprofit American Rivers, is thrilled at California’s change of heart on beavers. “It’s going to be awesome,” she says. “It’s a super fundamental change.”

Fair is helping to lead the charge to restore meadows in Sierra Nevada watersheds, which provide much of California’s drinking water in the form of snowmelt. Beavers could be key to this effort. About half of these high elevation meadows are degraded by historical grazing, roads, and stream channelization. Beaver dams slow stream flows and reconnect them with meadows.

This beaver dam in a Sierra Nevada meadow was presumably built by descendants of beavers reintroduced by the state in the 1900s. Photo by American Rivers.

Healthy meadows are a priority because they are biodiversity hotspots that attract an abundance of wildlife, and they serve as natural reservoirs. Meadows spread and slow snowmelt, soaking it up like sponges and releasing it gradually. Meadow restoration will likely become even more vital as the world warms, shrinking the snowpack and making it more critical to pace the release of snowmelt over the dry season.

“They’re a pretty important form of alternative water storage in the upper watershed,” Fair says.

Fair, like DeBloois, envisions installing beaver dam analogs (BDAs) before reintroducing beavers in some cases. Many streams in Sierra Nevada meadows are so deeply eroded, or incised, that the water runs too fast. “Incised channels are high energy,” she says. “The flow is concentrated and blows out beaver dams.”

Installing BDAs ahead of time will provide beavers a foothold in degraded habitats. “BDAs will give them something to build off of so they can make dams that last,” Fair says, adding that beavers also have the advantage of contributing “long term dam maintenance.”

Colorado River headwaters

Beavers could also be key to restoring meadows in headwaters of the Colorado River, which begins in the Rocky Mountains and is a major source of drinking water for Southern California. “They can help us recreate meadows faster than we can do it artificially,” says Felicia Marcus, a former California State Water Resources Control Board chair who is now a fellow at Stanford University’s Water in the West Program. “The more meadows the better.”

The Rocky Mountains have even more potential for meadow revitalization than the Sierra Nevada due to differences in terrain. “The Sierra are steep with small but important spots of meadows, while the Rockies have massive sweeps of meadows,” Marcus explains. “The scale for restoration is astonishing, it’s a huge opportunity to slow down and store water.”

“Beavers are the ultimate nature based solution,” she continues. “They do all the work—it’s free help.”

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