Make Way for Beaver

October 27, 2015

When a group of five scientists in the Pacific Northwest began advertising for workshops on the science of beaver restoration, they didn’t anticipate a few things.

The workshops would be filled to capacity within a week. There was so much interest they needed to increase both the workshop size and the total number of workshops offered. There would be a waitlist, followed by phone calls and emails from people clamoring to get in.

It wasn’t that the team was unprepared. This level of interest just wasn’t expected. After all, the relationship between beaver and humans has been strained for centuries. Fur trappers nearly wiped out the population entirely in the 1800s. Then, when the creatures came back in thriving droves, they were deemed havoc-wreaking pests.

But name after name appeared on the workshop registrations in Oregon, Washington, Alaska and California.

“People are starting to see the value of beaver for more than just their pelts or more than just pests, but how we can work in concert with them to fix more rivers and streams.”

Regulatory agency staff, nonprofits, tribal representatives, private landowners, members of the general public and others paid the $50 fee for one-day intensives on the science behind how beaver restore streams.

“We knew there were a ton of people out there working with beaver to restore waterways,” said Janine Castro, a geomorphologist with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service. “What we wanted to do was bring all these people together to synthesize knowledge on this topic and widely share science, information and management techniques.”

But the sharing of knowledge and best practices would live beyond the day-long events. Workshop discussions were captured in an official guidebook on beaver restoration, published this past June.

“The publication is meant to be an accessible resource for anyone using beaver to restore waterways,” said Greg Lewallen, a master’s student at Portland State University and the research assistant for the project. “With enough educational outreach, the perception of these animals will start to change. That’s why it’s critical we continue to spread the word about the large role that these animals play in ecosystems.”

Nature’s ecosystem engineers

Nature’s “ecosystem engineers” have a dramatic impact on water quality and quantity. Many river restoration groups now engineer what beaver have long done naturally.

“When wolves were reintroduced into Yellowstone, the effect cascaded throughout the entire ecosystem,” said Castro. “The similar, widespread effect can be seen with beaver.”


The ponds, pools and wetlands created by beaver dams expand both habitat complexity and area for birds, waterfowl, fish, aquatic invertebrates, mammals and amphibians.

While it was once common belief that fish could not pass through the dams, research now shows most native fish easily cross them.

“Large wood placement in streams was something that was pretty contentious 20 years ago,” said Castro. “There was huge concern about the risk, but education and outreach made a huge difference. Many landowners now realize this large wood has value. We’re hoping for the same thing with beaver.”

As the water overflows around the dams, natural floodplains are reconnected. New channels and wetlands are created. In Maine’s Acadia National Park, beaver contributed to an 89% increase in wetlands from 1944 to 1977. Studies have found similar results nationwide.

Increased presence of wetlands

As the “kidneys of the landscape,” the increased presence of wetlands often means a decreased presence of nutrients. The beaver restoration guide notes that ponds and wetlands created by dams can act as sinks for nutrients and toxins that would otherwise stimulate the growth of algae and other bacteria downstream. When beaver dams were removed from Taylor Creek in California’s Lake Tahoe basin, concentrations of phosphorus entering Lake Tahoe increased downstream.

Wetland sponges created by beaver dams also hold water in the system longer.

“Beaver slow the flow of water, reducing flash flooding and erosion and giving it the opportunity to recharge into the ground,” said Michael Pollock, ecosystem analyst with the National Marine Fisheries Service and another author of the guidebook. “When water is stored, it can later come out at low flow times, which is of course invaluable in the West.”

Beaver and climate resilience

In a changing world that forecasts the dry season to only become drier and longer, these creatures can make a big impact.

“Everyone is wondering what the West’s landscape will look like without the snowpack,” said Lewallen. “We can use beaver to create more climate resilient systems.”

Moreover they’re quite affordable. Some might spend tens to hundreds of thousands of dollars on some stream restoration projects that could be done for a fraction of the cost using the techniques outlined in the beaver restoration guide.

“There are things that we did to the landscape in the last 50 or 100 years — like build dams or straighten streams — and now we are trying to find ways to offset some of those impacts,” said Kent Woodruff, a biologist with the U.S. Forest Service and an author of the guidebook. “A lot of people understand that putting a natural engineer back on the landscape makes a lot of sense for a lot of reasons.

Storing water for the future

Woodruff leads Washington State’s Methow Beaver Project, a collaborative group of partners working to improve water quantity and quality by reintroducing beavers into strategic locations of the Methow Valley Basin. Nearly 300 beavers have been relocated to 51 sites over the last seven years.

Their tag line? Storing water for the future. One beaver at a time.

“I recognize there are plenty of places where beaver are not appropriate,” said Woodruff. “But where there are compatibilities and when we can increase our tolerance, we as a society are going to benefit.”

The scientists say the growing interest in our country’s diminished water quality and quantity may be behind the growing interest in beaver restoration.

“We should always be worried about water, and beaver have an immediate impact on this scarce resource,” said Castro. “It’s the fundamental thing that we all need to survive. People are starting to see the value of beaver for more than just their pelts or more than just pests, but how we can work in concert with them to fix more rivers and streams.”

Frequently Asked Questions About Beaver

How many species of beaver are there?
There are two: the North American beaver and the Eurasian beaver.

Is it true that beaver are rodents?
They are the largest rodent in North America and second largest in the world. The first is the capybara. Adult beaver typically weigh 35 to 71 pounds and can grow to a total length of four feet.

What do they eat?
As herbivores, beaver consume a wide variety of plant species. They eat the leaves, twigs, and inner bark of most types of woody plants that grow near the water. In addition, they eat many different kinds of herbaceous plants, including grasses, sedges and aquatic species such as water lilies. Despite common myths, beaver do not eat fish.

What do they use to build dams?
Dams are often constructed from a variety of material, both natural and manmade. Tree trunks, branches, twigs, bark, leaves, earth, mud, stones, cornhusks, plastic, metal and other debris have been documented in the structures.

Why do beaver build dams?
Beaver build dams to raise water levels. Higher water levels provide the following benefits:

  • Allows them to dive to safety from predators;
  • Increases foraging area and provides safe and easy travel routes to and from feeding areas;
  • Allows logs and branches to float within the pond;
  • Ensures that the entrances to lodges and burrows remain underwater, so as to protect beaver from land-based predators such as coyotes and cougars; and
  • In colder climates, keeps ponds at a sufficient depth to maintain liquid water under a sheet of ice during the winter months.

How big are the dams?
Dams can range in size from 20 inches to 930 yards long, as discovered in Alberta, Canada’s Wood Buffalo National Park.

How do beaver communicate?
They are highly social creatures that communicate through scent, vocal sounds, tail slapping and body movements. Tail slapping often serves as a warning signal.

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