Artificial beaver dams help Montana ranchers restore streams and protect wildlife

“People like to call streams the ribbons of life in the prairie,” said Leah Thayer, a restoration intern hosted by WWF’s Sustainable Ranching Initiative through the Montana Conservation Corps Individual Placement Program. “And less poetic way to say that is 80% of the wildlife species in the Northern Great Plains and in a grassland system rely on and use riparian corridors or stream corridors at some point in their life stage.”

WWF is working with partners to install artificial—or analog—beaver dams in streams on dozens of ranches in the Northern Great Plains. These structures aim to slow water flow, prevent harmful erosion, and distribute this precious resource throughout the landscape. The end result will raise the water table, improve soil health, nourish plants, and provide habitat for wildlife. We collaborated with The Nature Conservancy and Montana Conservation Corps to launch this program aimed at restoring water systems in grasslands in 2022.

Two years later, we’re finding that beaver dam analogs and related stream restoration are increasing available forage for livestock and providing more wildlife habitat.

“They see the healthy stream systems as a cornerstone in the health of their grass, which is the health of their cows, which is the health of their business,” Thayer said. “Whether beavers or humans are doing that, it's still going to have positive impacts on the stream system.”

Why do we need beaver dam analogs?

Moore Livestock, operating on a sweeping and varied landscape of hills, craggy outcroppings, and open prairie near Two Dot, Mont., is home to a series of natural beaver dams that transformed a portion of a stream into a sizeable pond in a low-lying area. The surrounding grasses are notably greener than the vegetation covering nearby higher ground, whipping in a brisk and relentless wind.

Rancher Sandford Moore, who works this land, muses that the dams—based on their size and location—have been in continuous use for hundreds of years, predating even his family’s 150-year-old business.

Historically, native beavers were almost extirpated due to the fur trade, which decimated their numbers until its decline in the mid-to-late 1800s. Though they’re still present in the Northern Great Plains today, they haven’t always been welcomed in agricultural settings. Beavers tend to plug up irrigation systems and chew through trees that some ranchers would prefer left standing.

Now the thinking around the presence of beavers on ranches and their benefit to riparian areas is shifting.

“Beavers are a blessing and a curse,” Moore said, “But they provide some really serious benefits in terms of raising the water table and spreading the water out. They provide habitat for all kinds of species.”

Beaver dam analogs work really well in areas where beavers are no longer present. And in some cases, beavers will return to the system and even build on top of a human-made structure. One rancher working with WWF spotted beavers swimming around the stream near where they’d installed beaver dam analogs only one year prior because the water was now deeper. Beavers already in the area ended up adding onto an analog and moving into the space.

“I can understand why people have a hesitation to beavers on their property,” Thayer said. “It’s been cool to see the shift in understanding how we can coexist with beavers and how a rancher’s bottom line can still be protected.”

Building a beaver dam analog

Building a beaver dam analog always starts with a conversation. Understanding a rancher’s goals for their livestock operation and the water flowing through the land is critical. Thayer and others will walk along the stream with those working the land to determine the best spots to place the structures. The biggest consideration is how and where the water will move once the dams are established.

Artificial beaver dams use natural materials—and almost all of them are sourced from the surrounding landscape. Workers begin by pounding a row of untreated wooden posts into the streambed about a foot or so apart from one bank to the other. Next, they weave thin, flexible branches clipped from nearby willows through the posts to create a permeable barrier. The final step is borrowed from beavers themselves: they pack mud, sand, dirt, roots, and plants on both the upstream and downstream sides of the willows to fill in some gaps and shore up the structure. Crisscrossing sticks placed perpendicular to the dam on the downstream create varied and chaotic pathways for the water to flow through.

“We’re trying to increase the complexity of how the water is moving,” Thayer said. “The water will hit that structure and find the nooks and crannies to move through. But it is just slowing the water down a little bit and giving it more of a chance to settle in the landscape and allowing the sediment that water is carrying to settle.”

Over time, this sediment will build up, raising the local water table and encouraging reconnection of floodplains—low-lying areas near bodies of water that flood when water levels rise because of rainfall, snowmelt, or other events. Natural floodplains provide wildlife habitat, improve water quality, and benefit communities. Areas with beaver dams or beaver dam analogs also tend to recover more quickly after a drought.

Artificial beaver dams benefit ranchers

Rancher Shane Moe, who also worked as a veterinarian, sits outside his gray stone home situated alongside a picturesque bend in the Musselshell River. A breeze rustles the verdant foliage arching over the water while ripples reflect the late afternoon sun. Rangeland fans out beyond this oasis.

“The river’s got a deeply personal effect on my life in terms of the wildlife that thrives here,” Moe said. “It’s a form of recreation for me. I enjoy paddling, just floating in the river and watching the wildlife and it's like a mini wilderness.”

As with any thriving landscape, water—the way it flows, its quality, how it’s absorbed and replenished—is at the center. Land use changes have impacted many freshwater systems in the Northern Great Plains over the past few centuries. Logging, agriculture, urban development, and other human activities can upend the delicate balance of the grasslands.

Moe is keenly aware of this fragility and committed to adding value to the larger ranching community by evaluating how his land use decisions affect others in the region. He wants more water in the ground to replenish aquifers and springs—a side effect of which is more productive land and an increase in wildlife.

“I feel like I have some responsibility for my downstream neighbors as being part of a watershed,” Moe said. “We're way up on the upper end and land management decisions that I have impact my neighbors 100 miles away through water quality and water availability.”

One such decision took place in 2023 when a crew came to Moe Ranch to install a series of beaver dam analogs along a narrow stream that winds through a pasture and spills into the Musselshell. Moe wanted to replenish aquifers and springs and, consequently, increase the productivity of the land and create better habitat for wildlife.

A year later, only the uppermost portions of most of these structures are visible and water is collecting behind them. This is an indicator of their success. Sediment buildup like this will cause the water to infiltrate into a wider expanse of soil—helping to retain nutrients, reduce drought stress, and provide food and habitat for wildlife. And nourished grasses and plants in the area can provide forage for livestock.

A brighter future for ranchers—and beavers

Restoring a landscape and the processes that help maintain the balance for wildlife and people is a lengthy and complex endeavor. But looking to nature itself for solutions can yield some of the best results. Beavers—and their elaborate engineering—remain critical to the dispersal and quality of freshwater in the Northern Great Plains. And in places where their numbers are still diminished, ranchers can still employ their expertise to much success.

“You hear stories of grasses that were stirrup deep and water every half mile on landscapes that are now very arid with water sources that are unreliable and far in between,” Moe said. “I would like to see the land that I'm managing turned back a hundred years where those grasses are healthier, soils are healthier, reverse some of the erosion that happened with the homesteading era, and allow beavers to do their thing and stop water on the landscape and spread out those riparian zones.”

Learn more about WWF’s Sustainable Ranching Initiative.

The stream restoration work conducted by WWF in the Northern Great Plains is supported through a partnership with Montana Conservation Corps, The Nature Conservancy, Winnett ACES, and Pheasants Forever. Stream restoration and other ranch-centric work in the Northern Great Plains is funded through WWF's Ranch Systems and Viability Planning network (RSVP), a comprehensive support system for ranchers to develop sustainable grazing management plans with assistance from on-the-ground technical specialists and to access continuing education to improve ecological outcomes at scale. J Bar L Ranch, Moore Livestock, and Moe Ranch work with WWF through this network. RSVP is funded by the US Department of Agriculture, the Arthur M. Blank Family Foundation, the National Fish and Wildlife Foundation, McDonald's, Cargill, the Walmart Foundation, Margaret A. Cargill Philanthropies, the US Fish and Wildlife Service - Partners for Fish and Wildlife, and the Knobloch Family Foundation.