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PHOTO CREDIT: Creative Commons "Beaver" by lsk208 is licensed under CC BY-NC-ND 2.0
History has not been kind to the American beaver (Castor canadensis). An estimated 400 million beavers called North America home before the European trappers arrived and decimated the population. By 1900, roughly 100,000 remained. Unbeknown to the trappers, the culling of the beavers forever changed the landscape and reduced water supplies.1
Early historical journals noted an American frontier brimming with pools and abundant wetlands.2 After the beavers were eliminated, their dams eventually washed away allowing creeks and rivers to straighten. The undammed rivers ran faster and their seasonal flows stopped sooner. The faster flows increased erosion, incised steep banks, and failed to nurture riparian plant species. Fast growing, often invasive, plant species took hold forever changing the landscape.
Even today there are some States and people who see North America’s largest rodent as a problem instead of a problem solver. They complain that beavers clog up culverts and create flooding problems on their land. Yet, maybe the beaver’s instinctive behavior isn’t entirely to blame. Afterall, we seem to have an insatiable desire to build homes closer and closer to nature.
Fortunately, the much-maligned beaver has been getting a resurgence of support. Researchers have rediscovered their value as “ecosystem engineers” and a new wave of “beaver believers” are embracing these fat, furry, and fascinating creatures as a possible solution to some of our water problems; a solution we especially need here in the arid West.3
Biologists, land managers, and even ranchers are now seeing the benefits of these industrious critters firsthand. Beavers instinctively build dams, which allows water to deepen and pool over a larger area. The beaver ponds “help moderate temperatures both by increasing water storage and encouraging exchange between surface water and groundwater exchange.”4 Deeper water is generally colder which helps support native fish species, such as trout and salmon, whose fry do better in a cooler environment. Plus, beaver ponds also provide a much-needed watering hole for other wildlife.
Equally important is the amount of water available for aquifer recharge at beaver ponds. Ben Dittbrenner, co-founder of Beavers Northwest, determined that “for every cubic meter (264 gallons) of surface water that beavers impound, another 2.5 cubic meters (660 gallons) sinks into the earth.”5
Beaver-created wetlands allow for additional plant growth and increase biodiversity. Studies at University of Manitoba and University of Stirling have noted increases in biodiversity at areas where beavers have been relocated.6 Dr Alan Law and Professor Nigel Willby of the University of Stirling, discovered “the number of species only found in beaver-built ponds was 50 percent higher than other wetlands in the same region.”7
Beaver ponds may even help improve farm yields. In an effort to reduce overgrazing, a group of ranchers in northwest Nevada allowed beavers to get reestablished on their land and the resulting changes were surprising.8 The ranchers noted that during times of drought, while other ranchers had to truck water for their livestock, they still had water on their land. Even more impressive, water from the beaver ponds was soaking into the ground “raising the water table and sub-irrigating the surrounding grasslands” which resulted in “fantastic grass production increases.”9
Beaver ponds have been shown to greatly reduce erosion and sedimentation.10 Beaver ponds next to agricultural areas have proven to also reduce phosphorus and nitrogen levels from farm run-off which greatly improves water quality for users downstream.11 In a 2015 study, scientists at the University of Rhode Island “determined that larger beaver ponds were able to remove up to 45 percent of nitrogen in the water that passed through them.”12
Here in Arizona, the USGS issued a report in April 2019 stating beavers reintroduced to the San Pedro River may have been responsible for enhancing recharge leading to an increase in groundwater elevation, which is very exciting for residents dependent upon groundwater who live near the San Pedro.13
Such positive results have garnered support from several groups of beaver believers which are promoting additional reintroduction activities.14 Just this past Fall, the Watershed Management Group performed a fundraiser to aid reintroduction activities at local waterways.15 Unfortunately, it costs a lot to reintroduce them and there are other concerns involving the long-term success of their reintroduction.16
Still, with all the benefits that beavers bring to a water-stressed area, we can only hope that State and Federal agencies and local beaver supporters will find the resources they need to move forward with reintroduction activities along many of Arizona’s waterways.
1. Mullen, Maggie. “Beavers An Unlikely Solution To Western Drought”, Wyoming Public Media, Aug. 24, 2018, http://www.wyomingpublicmedia.org/post/beavers-unlikely-solution-western.... Accessed Nov. 4, 2018.
2. Wheeling, Kate. “How Beavers Can Save Us From Ourselves” Pacific Standard, June 26, 2018, https://psmag.com/environment/the-world-that-beavers-created, Accessed July 2, 2018.
3. Koenigsberg, Sarah (Director & Editor). (2018). The Beaver Believers [Motion Picture]. USA: Tensegrity Productions
4. Public Library of Science, “Beaver dams may buffer against temperatures that threaten sensitive species”, May 17, 2017, https://phys.org/news/2017-05-beaver-buffer-temperatures-threaten-sensit.... Accessed Nov. 1, 2019.
5. Goldfarb, Ben. “The Re beavering of the American West”, The Atlantic, Dec. 4, 2018. https://www.theatlantic.com/science/archive/2018/12/relocating-beavers-s.... Accessed Dec. 16, 2018.
6. Perkins, Sid. “Beavers are engineering a new Alaskan tundra”, Nov. 28, 2018, Science News, https://www.sciencenews.org/article/beavers-are-engineering-new-alaskan-.... Accessed Dec. 9, 2018.
7. University of Stirling. "Beaver reintroduction key to solving freshwater biodiversity crisis", ScienceDaily, Aug. 26, 2019. www.sciencedaily.com/releases/2019/08/190826104844.htm Accessed Aug. 31, 2019.
8. Wernick, Adam. “Beaver Believers say dam building creatures can make the American West lush again”, Living on Earth, Sept. 22, 2018, https://www.pri.org/stories/2018-09-22/beaver-believers-say-dam-building... Accessed Oct. 2, 2018.
10. Wheeling, Kate. “How Beavers Can Save Us From Ourselves”
11. University of Exeter. "Beavers do 'dam' good work cleaning water." ScienceDaily, May 9, 2018. www.sciencedaily.com/releases/2018/05/180509121552.htm. Accessed May 10, 2018.
12. Petsko, Emily. “How Beavers Could Help Clean Up Polluted Waters Around the World”, Mental Floss, May 29, 2019, http://mentalfloss.com/article/582736/beavers-help-clean-polluted-waters. Accessed June 22, 2019.
13. Gungle, Bruce, Callegary, J.B., Paretti, N.V, Kennedy, J.R., Eastoe, C.J., Turner, D.S., Dickinson, J.E., Levick, L.R., and Sugg, Z.P., “Hydrological conditions and evaluation of sustainable groundwater use in the Sierra Vista Subwatershed, Upper San Pedro Basin, southeastern Arizona” (Ver. 1.3, April 2019), U.S. Geological Survey Scientific Investigations Report 2016-50114, https://doi.org/10.3133/sir20165114.
14. Brean, Henry. “River restoration group is eager for beavers to return to Tucson watershed”, Arizona Daily Star, Aug. 31, 2019. https://tucson.com/news/local/river-restoration-group-is-eager-for-beave.... Accessed Nov. 7, 2019.
15. “Beers, beavers and birthdays in store for Tucson this weekend”, Arizona Daily Star, Sept. 25, 2019, https://watershedmg.org/newsmedia/beers-beavers-and-birthdays-store-tucs.... Accessed Dec. 7, 2019.
16. Brean, Henry. “River restoration group is eager for beavers to return to Tucson watershed.”
17. Brean, Henry. “Dam shame: Beavers face second extinction on San Pedro River”, Arizona Daily Star, Oct. 7, 2019. https://tucson.com/news/local/dam-shame-beavers-face-second-extinction-o... Accessed Oct. 14, 2019.