VANCOUVER, Wash. - The use of artificial beaver dams to replicate the ecological benefits created by the industrious rodents shows promise for offsetting damage to fish habitat, water quality, and biodiversity arising from climate change.
But as the use of such "beaver mimicry" spreads, particularly in the Pacific Northwest, there are key gaps in the research and a need for more studies that examine whether the outcomes seen in specific projects are broadly applicable. That is a key takeaway from a new review of scientific literature by Washington State University researchers and others.
"There's a fair amount of active research, but the extent to which this practice is being implemented is far outpacing the research on the subject," said Jonah Piovia-Scott, associate professor in the School of Biological Sciences at WSU Vancouver and senior author of the paper. "There's a lot of good evidence coming out, but there's still a lot of work to be done to bridge the gap between the potential benefits and what's actually happening on the ground."
The lead author on the paper, published in the journal Restoration Ecology, was Jesse A.S. Burgher, who earned a PhD from WSU this year and is the wildlife program manager for the Cowlitz Indian Tribe. Other co-authors were Julianna Hallza, a current PhD student in Piovia-Scott's lab, and Max Lambert, director of science for The Nature Conservancy in Washington.
Beavers were once abundant in the Pacific Northwest, as well as across North America, but were driven to near-extinction in the 18th and 19th centuries.
The team evaluated 161 studies on a range of possible effects from beaver-related restoration efforts. They concluded there is substantial evidence that such efforts can make waterways more resilient to climate change, reducing summer water temperatures, increasing water storage, and enhancing flood-plain connectivity. They also can enhance biological diversity and build resistance to wildfires.
Beavers were once abundant in the Pacific Northwest, as well as across North America, but they were driven to near-extinction in the 18th and 19th centuries by the fur trade, which fueled economic expansion and early white settlement. Beaver populations have rebounded to a degree, but remain far below those earlier levels.
Efforts have been increasing to restore beaver populations and mimic the beneficial effects of the deep ponds created by their dams, as climate change threatens to diminish waterways and riparian areas, as well as the many species that rely on them.
Such projects have become especially common in the Pacific Northwest with the use of human-made "beaver-dam analogs." In some cases, the dams are meant to simply replicate the effects of beaver structures; others are intended to attract beavers to recolonize waterways.
"This practice has become more and more widespread in our region," Piovia-Scott said. "These are going in all over the place in the Pacific Northwest."
One such example is a project along Oregon's Bridge Creek, a tributary to the John Day River. Ecologists there have implemented a series of artificial dams - woven from willows and other plant materials - that have led to growth in the population of threatened steelhead and other fish.
It's unknown whether those results would apply in other places with different ecological characteristics or for projects of differing sizes.
"That series of studies is fantastic and it's really a great example of how these beaver-mimicry practices can improve fish habitat and contribute to fish-population growth," Piovia-Scott said. "It's not at all clear whether those benefits will accrue in other systems."
Piovia-Scott said that his research work, which focuses on the effects of beavers and beaver dam analogs on a variety of wildlife, has led to important partnerships with tribes, non-profits and other groups focused on beaver restoration that may lack the resources to conduct scientific research themselves. Such partnerships are crucial to developing the best ecological approaches, he said.
"I work with a lot of restoration practitioners, and they have way more on-the-ground expertise in so many things than I do as a researcher," he said. "What they don't have is a lot of capacity to conduct large-scale research projects - they may have the skills, but it's usually not what their organizations are funded to do. So, there's a tremendous amount of knowledge around restoration practices that can be generated through these partnerships."
