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Beavers on the Border

Even as an Arizona native, the thought of finding beavers in the riparian areas of the borderlands never occurred to me. Even seeing them in the lakes and creeks of northern Arizona feels like a rare and exciting experience. Kayaking across the lakes nestled in the ponderosa forests, we've seen a lot of evidence of beavers - once, Thomas and I were lucky enough to paddle by a beaver as it swam towards home. At the mouth of the lake, dams terraced on top of each other create a wetland full of willows. This ever-changing and ever-moving mosaic of earth and water provides critical habitat for wildlife and some of the most essential ecosystem services in our current climate: water supply, flood management, erosion control, and fire protection.

Beaver dam in northern Arizona.
Beaver dam in northern Arizona.

The North American beaver (Castor canadensis) has a complicated image. Some see them as nuisances, damming water and preventing it from reaching land further downstream. But in reality, they don't dam up water completely (and they're not 700 feet tall like man-made concrete dams). They slow water down and allow it to pool before continuing on downstream. While it may seem counterintuitive to landowners and recreationists who rely on water for their livelihood to slow water, it is vital for the health of the entire ecosystem, and the benefits cascade for miles by keeping ecosystems in balance. Water retention not only recharges groundwater, but keeps water available at the surface. This acts as a natural fire break when wildfires ignite - an increasing occurrence due to climate change, making beaver wetlands more critical than ever.

Beaver ponds on Little Last Chance Creek, California, stayed green during a wildfire. Video: Emily Fairfax.

In recent years, there have been efforts to restore beavers to the borderlands region as part of broader conservation initiatives aimed at restoring riparian ecosystems and enhancing water retention in arid landscapes. Reintroducing beavers can help improve water quality and availability, raise the water table, and create habitat for various other species. Two main areas that could be introduced to are the San Pedro River and the Las Cienegas National Conservation Area.

The San Pedro River, flowing north from Mexico into southeastern Arizona, has a complex ecological history involving beavers. While records suggest that beavers were once present in the region, they were locally extirpated due to overhunting and habitat loss when fur trappers moved into the region in the 19th century. Beavers are known to thrive in riparian habitats like those found along the San Pedro River, where they construct dams and lodges, creating wetland ecosystems that benefit numerous other species and sustain important species like cottonwood trees.

The first eight beavers were reintroduced to the San Pedro Riparian National Conservation Area along the US-Mexico border 25 years ago. After several more supplemental introductions, the population began to rise. By 2010, over 30 dams had been constructed, and an estimated 100 individuals lived along the San Pedro River. Then, suddenly, populations seemed to plummet, possibly due to mountain lion predation or human activity. Thanks to dedicated employees and volunteers who survey the area, like the Friends of the San Pedro River, these changes have been monitored. Most recently, signs of a gradual increase have been noted with the help of surveys and wildlife cameras, which have documented more dams, gnawed tree trunks and branches, and photos of their nighttime behavior.

Beavers at work along the San Pedro River in southeastern Arizona. Video: Steve Merkley of Cochise College.

Thanks to advocacy work by organizations like Watershed Management Group, who are working to restore riparian areas with beaver-based restoration practices, progress is being made in the international San Pedro River watershed, and plans have been made for re-establishing beavers in the Las Cienegas National Conservation Area.

With continuing hotter and drier trends due to climate change, beaver-based restoration projects could be vital to preserving our few and precious riparian resources. Embracing beaver dams and protecting the wetlands they create will improve landscape resiliency for all.

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