Restoring watersheds, one beaver dam at a time

In the arid landscapes of the western United States, water is everything. Streams can be few and far between, but they support a diverse array of wildlife, sustain working lands, recharge groundwater and provide a buffer against the negative effects of drought and wildfire. Yet many of the rivers and wetlands in the West have become increasingly vulnerable as prolonged drought, altered fire regimes and decades of habitat degradation strain already limited water resources.

Enter one of the region's most effective restoration partners: the North American beaver.

Often called an "ecosystem engineer," beavers can transform landscapes in ways that other animals can't. By building dams and creating ponds, they can keep water on the landscape for longer, which helps raise water tables and allow streams to flow later into the summer and reduces the effects of drought. Beaver complexes also improve nutrient retention, and can even serve as natural fire breaks during wildfires. And their work benefits other species, too. A single beaver colony can turn a narrow channel into a network of ponds and wetlands that support countless fish, mammals, birds, amphibians and plants, in addition to providing water for livestock, increasing the resilience and productivity of ranches and farms.

The need for this kind of natural infrastructure is rooted in the loss of beavers and wetlands across North America. Intensive trapping for the fur trade dramatically reduced beaver populations in the 19th and early 20th centuries, leaving many streams without the dam-building activity that once helped sustain wetland ecosystems. At the same time, wetlands themselves have continued to disappear. The lower 48 states have lost 50 percent of their wetlands, down to around 100 million acres from an estimated high of more than 220 million acres in the 1600s. These losses are especially consequential in the arid West, where wetlands and riparian areas make up less than 2 percent of the land area in the Intermountain West but support more than 80 percent of the region's wildlife species. Although beavers have rebounded from their historic lows, many of the watersheds they once helped shape remain degraded, disconnected and less resilient to environmental stressors.

This is why conservation practitioners are increasingly "thinking like a beaver" and relying on low-tech process-based restoration (LTPBR) approaches. These techniques-including beaver dam analogs (BDAs) and post-assisted log structures (PALS)-mimic the function of natural beaver dams using simple materials like wood posts and willow branches. Often, these structures are designed not just to restore habitat on their own, but to make a stream attractive enough that beavers move back in and take over the work themselves.

Through programs such as RESTORE Colorado and Southwest Rivers Headwaters Fund, NFWF is supporting efforts across the West that restore wetlands, reconnect floodplains and, in some cases, help bring beavers back to places where they have long been absent.

One example can be found in Colorado's Kawuneeche Valley near the headwaters of the Colorado River.

Historically, beavers helped maintain extensive wetlands throughout the valley. But as beaver populations declined, the overall ecosystem shifted from wetlands to grasslands and contributed to a loss of surface water, increased erosion and declining habitat quality.

To address this decline, the Northern Colorado Water Conservancy District used a $300,000 grant awarded through the RESTORE Colorado Program to attract beavers back to the Kawuneeche Valley and help reverse the ecological and hydrological degradation that has occurred in their absence. The effort involved restoring floodplain habitat, improving stream function, removing invasive vegetation and installing 29 beaver dam analogs. The project not only helped improve the quality and quantity of agricultural and drinking water, it also serves as a vital investment in water availability for future generations.