The Sign of the Beaver in the Great Central Valley

The North American Beaver (Castor canadensis) is unapologetically one of my favorite mammals.  Considered pests by some, this large rodent is a master ecosystem engineer and keystone species in its environment.

During the 19th century, the humble beaver was nearly eradicated from the western United States, including California, through habitat loss, hunting and trapping for fur, and deliberate extermination.  The beaver is sometimes considered a nuisance species, since their enthusiastic lumberjack work may cause trees to fall across roadways, and their dams, ponds and levee burrows can cause flooding.  But it turns out that the beaver provides a suite of unexpected ecosystem services, including increasing wildlife habitat and water storage potential in the arid, drought-prone west. 

Beaver lodge at San Luis National Wildlife Refuge, April 2017

Beavers are hydro-engineers and excel at altering the flow of water though the environment.  The familiar "beaver dams" these large rodents create form small reservoirs, pools of quiet water in otherwise rapidly flowing aquatic environments.  Without beaver and their log-and-stick dams, water rushes downstream, eroding stream channels and sweeping fish down the river.  In the quiet waters of beaver ponds, however, valuable fish such as juvenile salmon are able to thrive.  Some speculate that the decline of salmon in the west is due in part to the loss of beaver and the habitat they create. 

Beaver track in wet sand, San Joaquin River National Wildlife Refuge, January 2017

Beaver ponds are thriving ecosystems in themselves, creating habitat for a number of wildlife species.  The California Department of Fish and Game states,

          "Beaver dams create habitat for many other animals and plants of California. Deer and
          elk frequent beaver ponds to forage on shrubby plants that grow where beavers cut down
          trees for food or for use in constructing their dams and lodges. Weasels, raccoons, and
          herons hunt frogs and other prey along the marshy edges of beaver ponds. Sensitive
          species such as red-legged, yellow-legged and Cascade frogs all benefit from habitat
          created by beaver wetlands. Migratory water birds use beaver ponds as nesting areas and
          resting stops during migration. Ducks and geese often nest on top of beaver lodges since
          they offer warmth and protection, especially when lodges are formed in the middle of a
          pond. Willow flycatchers use the shrubby re-growth of chewed willow stumps to seek
          shelter and find food. The trees that die as a result of rising water levels attract insects,
          which in turn feed woodpeckers, whose holes later provide homes for other wildlife. In
          coastal rivers and streams, young coho salmon and steelhead may use beaver ponds to
          find food and protection from high flows and predators while waiting to grow big enough
          to go out to sea." 
          Source: California Department of Fish and Wildlife publication, Living With Beavers

Evidence of beaver activity along the Tuolumne River, Stanislaus county, March 2016

In addition to wildlife habitat, beavers and their ponds provide hydrologic benefits to arid, often drought-stricken regions.  Beaver ponds capture and hold water, preventing it from rushing quickly downstream and eventually being lost to the sea.  Water held in beaver ponds is able to slowly percolate into the ground, increasing groundwater storage and soil hydration.  This ability of the soil to recharge itself makes the land much more resilient in the face of drought.

Evidence of beaver activity along the Tuolumne River, Stanislaus county, March 2016

In California, beaver still occur in the Great Central Valley, parts of the Sierra Nevada and the Cascades, and most of the northern third of the state.  Historically, beaver occurred along the coast of California as well.  I have seen evidence of beaver activity in the Great Central Valley as well as in the Sierra in the form of fallen trees and tooth marks, tracks, and stick lodges.  A beaver sighting is always an exciting event!

Beaver track in wet sand, San Joaquin River National Wildlife Refuge, January 2017

After years of the systematic depredation of the beaver, interest in California's beaver population is growing.  In light of the potential benefits of beaver ponds to fish (specifically salmon) and other wildlife, as well as ponds' potential for surface water storage and ground water recharge, it seems that beavers and their activity benefit the entire watershed.

Beaver tooth marks on a cottonwood log along the Tuolumne River, March 2016 
 

Comments

  1. kate.lundquistApril 5, 2018 at 1:59 PM

    Hi Siera! Great to read your post on beaver. My colleague Brock Dolman and I at the Occidental Arts and Ecology Center WATER Institute have been working to create a culture of beaver stewardship in California for well over a decade (www.oaec.org/beaver) and have a great stewardship guide for those interested in learning more (free download at https://oaec.org/publications/beaver-in-california/). For a little context, we worked for three years to get the CDFW to post information about beaver coexistence and are grateful they finally agreed to use the Living With Beaver information we provided them (source of your quote). There is still a great deal of work to do as beaver are not protected by the state and are still seen as a threat to agriculture and infrastructure. Thanks for putting the good word out! Cheers, Kate Lundquist.

    ReplyDelete
  2. Siera NystromApril 8, 2018 at 2:05 PM

    Hi Kate!
    Thanks for reading, and for the great work that you do! I've read through your beaver stewardship guide and am including the links to the Bring Back the Beaver Campaign and pdf on the Resources page of my blog - great information that needs to be shared! Thanks again!
    Siera Nystrom

    ReplyDelete

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