Learning from beavers to bring life back to degraded meadows

Story by Sophie Hamann, Deputy Public Affairs Officer

Often called “ecosystem engineers,” beavers benefit wetland habitat simply by building dams. Using strong teeth and natural instincts, they can improve critical functions of meadow health by raising the water level, improving water quality and reconnecting floodplains.  

It begs the question, “what can we learn from beavers?” 

Since beavers can’t be hired to create dams, the human employees of the Tahoe National Forest and partners from the South Yuba Citizens League are building structures that mimic what beavers build in their natural environments. Beaver Dam Analogues (BDAs) and Post Assisted Log Structures (PALS) are human-made, low impact structures that enhance the ecological and aesthetic value of meadows.  

The absence of beavers partially due to trapping and habitat loss combined with the impacts from over grazing and logging in the past, have resulted in deeply degraded meadow ecosystems across the Tahoe National Forest. After shouldering these impacts for over a century, five high-elevation meadows in the Yuba River Ranger District have been selected for restoration using BDAs and PALs. 

“BDAs and PALs can accelerate the recovery of our meadow ecosystems by reducing water velocities, increasing sediment deposition, enhancing floodplain connectivity, raising groundwater levels and increasing habitat complexity,” said hydrologist Karl Ronning, who is working to restore meadow health across the Tahoe National Forest. 

In other words, BDAs and PALs will act as “speed bumps” to slow and filter the water, setting off a chain of ecological events that result in more resilient wetland habitat for high elevation aquatic species, migratory birds and terrestrial wildlife. 

Restoring these meadows is the foundation for which ecosystem services can thrive, such as habitat for hundreds of species along with recreational and economical value to humans. Considering these meadows sit at the headwaters of the North Yuba River, restoration has the potential to benefit the greater watershed, thus increasing ecosystem value, water quality and climate resilience for downstream users.  

Rather than using expensive heavy equipment, BDAs and PALS are a low-risk, cost-effective and proven method of restoration. Taking anywhere from 20 minutes to an hour based on crew size, constructing a BDA is quick and simple. The human-made dams are constructed by weaving a mat of branches through upright posts that are driven into the ground across the channel. Sediment, stone and plant material are placed on the upstream side and “voila!” the water starts to rise, and the crew quickly sees the effects of their labor.  

“Beneficial results are immediate,” said Ronning, “Keeping the groundwater table higher during the dry season will allow a shift to wet meadow vegetation and cascading benefits to the greater meadow ecosystem.” These cascading benefits are especially important in the face of a changing climate where the landscape has been significantly degraded and beavers are no longer active. 

Image 1: Forest Service hydrologist and swift water design technicians build a beaver dam analog in Chapman Saddle Meadow, one of the five high-elevation meadows selected for rehabilitation. Photo by Jacob Burdick, USDA

Image 2:Beaver dam analog built at West Church Meadow in the Yuba River Ranger District. Photo by Karl Ronning, USDA