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Water-related issues columns from Prescott AZ Daily Courier "Science Works" 
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Prescott Beaver Believers

 Given Prescott’s many creeks, naturalists generally believe beavers lived there before white settlement. But they dispute reports that these furry dam builders currently reside within our city limits. Ecologist Greg Murray helped me flag one such report on the iNaturalist website as an April Fool’s Day joke. Some, like Prescott Creeks’ Executive Director Michael Byrd, tell visitors to Prescott’s Watson Woods Riparian Preserve, who see what looks like beaver damage to trees, that humans girdling Siberian Elms—an undesirable invasive species—caused this. Yet many area nature lovers fit into a more broadly defined “beaver believer” category and may look to them when thinking about the future of their favorite rivers. Do beavers play a key role in maintaining watershed health?

 Before considering that question, consider some background. A review of the book Beaverland—How One Weird Rodent Made America by Leila Phillip in the December 2022 Scientific American magazine begins by saying, “Beavers, you may have noticed, are having a moment.” It goes on to say, “The Los Angeles Times recently called the beaver a ‘superhero’ and the New York Times has deemed them ‘furry weapons of climate resilience.’” And additionally “wetlands with beavers are so good at fighting mega-fires that some researchers have urged the US Forest Service to switch mammal mascots from Smokey Bear to Smokey Beaver.”

 A web page posted by the non-profit Watershed Management Group suggests that Tucson has lots of beaver believers. It’s headlined “Release the Beavers!” —followed by “Help beavers reclaim their role as a keystone species in the Santa Cruz and San Pedro watersheds. Wiped out by trappers in the 1800s, they are returning to restore our desert rivers.” Besides advocating for restocking beaver, they conduct annual surveys to monitor the health and distribution of beaver populations, and work to understand “how beaver dams can help flowing water sink into the aquifer below and recharge groundwater.”

 Prescott beaver believers have similarly been at work. In the summer of 2009, students in Prescott College professor Walt Anderson’s Wetland Ecology and Management class counted seven dams and 17 beaver colonies along a 20-mile stretch of the upper Verde River in a study funded by The Nature Conservancy.  These data—and observations of chew marks on trees—led to an estimate of 1 to 1.5 beaver colonies per mile. Combined with Walt’s estimate of six beavers per colony, one concludes that beavers were thriving there 15 years ago.

 How are beavers doing on the Verde River today?  Sadly, where Walt and students found a thriving population, local Sierra Club Chair Gary Beverly tells me that, based on recent excursions, the beaver population appears to have crashed. Why? Walt thinks disease and predation are most likely responsible. Gary suggests decreased water base flow in recent decades —from 28 cfs to 13 cfs—due to groundwater pumping from the Big Chino aquifer and climate change is a factor.

 Besides drought and increased wildfire, climate change can lead to more severe rainfall events and flooding. Beaver dams help an ecosystem retain more water, making it more resilient to drought.  Moreover, by slowing water flow, the work of these natural engineers reduces erosion and allows sediments to settle before they're carried to lakes downstream.  And since nutrients like phosphorus that promote the growth of "nuisance" algae and aquatic plants are mostly carried on sediment, beaver dams improve water quality downstream. Greg tells me that aerators recently installed in Watson Lake combat oxygen depletion in deeper waters driven by excessive surface algae and plant growth— a problem that could be minimized by beavers upstream freely performing “ecosystem services” that help maintain biodiversity and water quality. Walt questions whether Granite Creek now carries enough water to reliably support beavers—something it once did.

 Gary has suggested that introducing beavers could benefit stretches of the upper Verde River overrun by cattails—something beavers like to eat and use in dam building, along with cottonwoods and willows. 62% of the Verde River watershed is public land—most under the jurisdiction of the US Forest Service (USFS). In wildlife terms, the USFS is only responsible for managing habitat—otherwise it co-operates with the Arizona Game and Fish Department (AZGFD) and the U.S. Fish and Wildlife Service. AZGFD wildlife specialist April Howard tells me that her agency “has no plans to restock beaver anywhere in Arizona,” and reversing that decision “would require a lot of analysis.” One reason for hesitancy: uncertainty as to how beavers would affect native fish threatened by non-natives. Another: beavers can move around and become pests!

These topics will be discussed at the “2024 State of the Verde Watershed Conference” beginning September 24^th in Camp Verde. Also that night, in Tucson, the “6th Annual Beavers & Brews” gathering will be held—billed as appropriate for “beaver believers new and old.”

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September 8, 2024 / Reader Feedback and Responses

Courier Column for September 8 "" / Comments

from GM: The Sunday column came out great!  Thanks for doing those - this town needs it!

response from S. Cook:  Thanks.

from September 17, 2024 Prescott Daily Courier:

   response from S. Cook:  Thanks.

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link to Prescott's Citizen Water Advisory Group

link to Courier Climate Dialogues page