Hunted to near-extinction in the 19th century, beavers may be crucial to counteracting some of climate change’s drying effects in the mountainous Pacific Northwest, where their dam habitats were found in new research to provide refuge for several threatened amphibian species.
The findings could lend support to relocation efforts that have aided in the slow recovery of the state animal of Oregon but are controversial among some West Coasters, say the Washington State University Vancouver researchers who authored the study, published in Freshwater Biology in November.
Beavers have long been understood to create ecological heterogeneity that supports organisms such as fish, birds and insects, but their contribution to amphibians in the Cascade Range, which extends from southern British Columbia into Northern California, has been less examined.
Surveying 49 sites in Gifford Pinchot National Forest in southern Washington, about three-fifths of which were beaver-dammed, the researchers found that amphibian species richness was 2.7 times higher in dammed areas. The biggest beneficiaries appear to be slow-developing species such as red-legged frogs and northwestern salamanders, whose presence almost exclusively at dammed sites suggests some amphibians’ successful reproduction relies heavily on these habitats.
By bringing less snowpack and higher temperatures, climate change is expected to dry up aquatic ecosystems in the mountains of western North America, meaning viable habitats for amphibians, including those examined in the study, will shrink. This will put pressure on animals like frogs, whose tadpoles need time there to survive metamorphosis before becoming land-dwelling adults.
“Pond-breeding amphibians need a pond, and if your pond dries up too fast, then you no longer have habitat to breed in,” said Jonah Piovia-Scott, a study co-author and assistant professor at WSU’s School of Biological Sciences whose namesake lab is where the new research originated. “We’ve seen this occur; you see dried-up ponds with tadpoles in the bottom of them.”
However, “Beavers can actually make that habitat remain on the landscape, even as the climate changes,” Piovia-Scott explained.
As semi-aquatic animals that live primarily in the water, beavers build dams that create large and deep pond-like habitats that stay covered in water all year. While helping beavers hide from predators, the dam construction provides shelter for other species, as well.
“We suggest that slow-developing amphibians and some variable-rate developers might benefit greatly from beaver restoration,” the study says. “Beavers could therefore be useful and important components of ecosystem-based restoration, management and climate adaption, especially in parts of their native ranges in North America or Eurasia predicted to undergo climatic drying.”
The Southern Washington Cascades has been designated a priority conservation area by Partners in Amphibian and Reptile Conservation, whose steering committee is composed of nearly a dozen representatives from federal agencies.
But beaver restoration can be a touchy subject, even though Piovia-Scott said there’s wide agreement that the animals were once very abundant in the Pacific Northwest and that it’s generally a good thing to have them back on the landscape, so long as they don’t become a backyard nuisance.
In Washington, initial beaver relocations were conducted by Native American tribes, which have special federal permission for such efforts. The Evergreen State now has non-tribal relocation projects.
However, although the North American beaver is also native to California, there’s less agreement there about its historic abundance and distribution, according to Piovia-Scott.
Noting the potential of beavers to conflict with agriculture, roads, infrastructure and human safety, the Golden State’s fish and wildlife department does not issue relocation permits, but urges residents to, "Please consider living with beavers to help support California beaver populations and their benefits to terrestrial and aquatic habitat.”
But even in California, beavers may offer other benefits. Beaver ponds could also help protect land from flames in the wildfire-stricken state, academics in the state have found.
For his part, Piovia-Scott is looking even further into beavers' impact. In collaboration with the Washington Department of Fish and Wildlife, his current project is radio-tracking translocated beavers to see how well they stick, and ultimately, to better gauge their actual ecological impacts, such as whether their presence draws new species.
“I think there's a general sense that they will provide all of these ecological benefits as long as they're not harming infrastructure, but it’s not exactly clear that that’s true,” he acknowledged.
Piovia-Scott wants to build a better dataset by examining areas before and after translocation, as well as comparable sites where no relocation happened.
“My hope is that as more and more people see the benefits of beavers and the beneficial impacts they can have on amphibians and other wildlife species, they will increasingly support a restoration of beaver to the landscape,” he said.
“Not only will that be great for the beavers,” he continued, “It will also help many other wildlife species that we might care about, and really facilitate ecological diversity in the mountains of western North America and contribute to the resilience of all of these native species to climate change.”
The study “Beaver dams are associated with enhanced amphibian diversity via lengthened hydroperiods and increased representation of slow‐developing species,” published Nov. 27 in Freshwater Biology, was authored by John M. Romansic, Nicolette L. Nelson, Kevan B. Moffett and Jonah Piovia‐Scott, Washington State University Vancouver.