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The Science: Ecosystem Services

The North American beaver (Castor canadensis) is a uniquely important aquatic mammal with a profound role in ecosystem and watershed maintenance and restoration. Commonly called an “ecosystem engineer,” beaver transform the landscape, creating healthier, more resilient watersheds, improving water quality, increasing the availability of fresh water, forming essential wetlands, reducing peak flood levels, limiting damage from forest fires, mitigating climate change, and helping other fish and wildlife species to survive a warming planet. Beaver are considered a keystone species because of this disproportionately large impact they have on the entire surrounding ecosystem, establishing critical habitat for a large variety of fish, amphibians, birds, and mammals. CLICK HERE to download these studies as a PDF.

Beavers Support Biological Integrity

Integrity refers to an unimpaired condition, a state of being complete or undivided. Biological integrity has been defined by the US EPA, as [t]he ability to support and maintain a balanced, integrated adaptive assemblage of organisms having species composition, diversity, and functional organization comparable to that of natural habitat of the region.” This is a result of evolution; each organism is adapted to the environmental conditions in its native biogeographic region. An environment that supports an assemblage of organisms similar to that produced by long-term evolutionary processes has high biological integrity. Changes that result from human activities cause a divergence from biological integrity. Beavers build biological integrity in streams. 

Beavers Create Flood Water Storage

A 2020 study found that restoring beaver to the Milwaukee River Watershed could reduce the peak flow during high water events by over 37% on average and provide as much as $3.346 billion in ecological services by creating stormwater storage to prevent downstream flooding. Researchers also estimated that beaver wetland restoration could protect over 500 homes that are currently in the floodplains, protecting these communities from potential destruction of infrastructure. Restoration of wetlands and floodplains has also been identified as an important climate adaptation strategy to reduce flood risk and protect water quality in the Midwest.

Beavers Increase Biodiversity and Species-Richness

Beavers Increase Biodiversity and Species-Richness. The ponds and wetlands that beaver create provide habitat and forage areas for other aquatic mammals such as mink, muskrat and otters; raptors such as eagles and osprey; rare songbirds such as Kirtland’s warblers; waterbirds such as the endangered whooping crane, and a wide variety of reptiles, amphibians, and insects. Due to the uncertainty of climate change, beaver activity plays an increasingly critical role in maintaining and stabilizing habitat for a wide range of wetland-dependent species. 

  • Anderson, N. L., Paszkowski, C. A., & Hood, G. A. (2014). Linking aquatic and terrestrial environments: Can beaver canals serve as movement corridors for pond-breeding amphibians? Animal Conservation, 18(3), 287–294.  

  • Cooke, H. A., & Zack, S. (2008). Influence of beaver dam density on riparian areas and riparian birds in shrubsteppe of Wyoming. Western North American Naturalist, 68(3), 365–373.[365:iobddo];2 

  • Law, A., Gaywood, M. J., Jones, K. C., Ramsay, P., & Willby, N. J. (2017). Using ecosystem engineers as tools in habitat restoration and rewilding: Beaver and wetlands. Science of The Total Environment, 605–606, 1021–1030. 

  • LeBlanc, Gallant, Vasseur, & Léger (2007). Unequal summer use of beaver ponds by river otters: Influence of beaver activity, pond size, and vegetation cover. Canadian Journal of Zoology, 85(7), 774–782. 

  • Zero, V. H., & Murphy, M. A. (2016). An amphibian species of concern prefers breeding in active beaver ponds. Ecosphere, 7(5),  

  • Hood, G. A., & Larson, D. G. (2013). Beaver-created habitat heterogeneity influences aquatic invertebrate assemblages in Boreal Canada. Wetlands, 34(1), 19–29. 

  • Hossack, B. R., Gould, W. R., Patla, D. A., Muths, E., Daley, R., Legg, K., & Corn, P. S. (2015). Trends in Rocky Mountain Amphibians and the role of beaver as a keystone species. Biological Conservation, 187, 260–269. 

  • Nummi, P., Liao, W., Huet, O., Scarpulla, E., &; Sundell, J. (2019). The beaver facilitates species richness and abundance of terrestrial and semi-aquatic mammals. Global Ecology and Conservation, 20:1.   

Beaver Support Fish Populations

Numerous academic papers and peer reviewed studies now show that beaver complexes have a significant beneficial impact on trout and salmonid species, because they increase forage, create greater biodiversity, improve stream health and water quality, reduce flooding, and stabilize stream temperature. It is critical to examine newer studies that debunk outdated assumptions about beaver-trout relationships. 

  • Bouwes, N., Weber, N., Jordan, C. E., Saunders, W. C., Tattam, I. A., Volk, C., Wheaton, J. M., & Pollock, M. M. (2016). Ecosystem Experiment reveals benefits of natural and simulated beaver dams to a threatened population of steelhead (Oncorhynchus mykiss). Scientific Reports, 6(1).

  • Johnson-Bice, S. M., Renik, K. M., Windels, S. K., & Hafs, A. W. (2018). A review of Beaver salmonid relationships and history of management actions in the Western Great Lakes (USA) region. North American Journal of Fisheries Management, 38(6), 1203–1225. 

  • Law, A., McLean, F., & Willby, N. J. (2016). Habitat Engineering by Beaver Benefits Aquatic Biodiversity and ecosystem processes in agricultural streams. Freshwater Biology, 61(4), 486– 499. 

  • Lokteff, R. L., Roper, B. B., & Wheaton, J. M. (2013). Do beaver dams impede the movement of trout? Transactions of the American Fisheries Society, 142(4), 1114–1125. 

  • McCaffery, M., & Eby, L. (2016). Beaver activity increases aquatic subsidies to terrestrial consumers. Freshwater Biology, 61(4), 518–532. 

  • Popelars, J. (2008). Using GIS to Reevaluate Beaver Dam Effects on Local Environments in Northern Wisconsin Brook Trout Streams During the 1980s. Graduate Thesis. Department of Resource Analysis, Saint Mary’s University of Minnesota, Winona, MN 55987. 

  • Smith, J. M., & Mather, M. E. (2013). Beaver dams maintain fish biodiversity by increasing habitat heterogeneity throughout a low-gradient stream network. Freshwater Biology, 58(7), 1523–1538. 

  • Wathen, G., Allgeier, J. E., Bouwes, N., Pollock, M. M., Schindler, D. E., & Jordan, C. E. (2019). Beaver activity increases habitat complexity and spatial partitioning by Steelhead Trout. Canadian Journal of Fisheries and Aquatic Sciences, 76(7), 1086–1095. 

Beavers Stabilize Stream Temperature

Recent studies have shown how beaver ponds and wetlands stabilize stream temperatures during times of fluctuation. Stream temperature is critical to maintaining a stable hydrological system for species, such as trout, to survive. 

  • Dittbrenner, B. J., Schilling, J. W., Torgersen, C. E., & Lawler, J. J. (2022). Relocated beaver can increase water storage and decrease stream temperature in headwater streams. Ecosphere, 13(7). 

  • Majerova, M., Neilson, B. T., Schmadel, N. M., Wheaton, J. M., & Snow, C. J. (2015). Impacts of beaver dams on hydrologic and temperature regimes in a mountain stream. Hydrology and Earth System Sciences, 19(8), 3541–3556.  

  • Weber, N., Bouwes, N., Pollock, M. M., Volk, C., Wheaton, J. M., Wathen, G., Wirtz, J., & Jordan, C. E. (2017). Alteration of stream temperature by natural and artificial beaver dams. PLOS ONE, 12(5). 

Beavers Improve Water Quality

Beaver ponds remove nutrients such as nitrogen and phosphorus and sediment. Breaching beaver dams destabilizes and releases sediments causing increased sediment loads downstream. 

  • Lazar, J. G., Addy, K., Gold, A. J., Groffman, P. M., McKinney, R. A., & Kellogg, D. Q. (2015). Beaver Ponds: Resurgent nitrogen sinks for rural watersheds in the Northeastern United States. Journal of Environmental Quality, 44(5), 1684–1693. 

  • Levine, R., & Meyer, G. A. (2014). Beaver dams and channel sediment dynamics on Odell Creek, Centennial Valley, Montana, USA. Geomorphology, 205, 51–64. 

  • Puttock, A., Graham, H. A., Carless, D., & Brazier, R. E. (2018). Sediment and nutrient storage in a Beaver Engineered Wetland. Earth Surface Processes and Landforms, 43(11), 2358–2370. 

Beavers Support Hydrological Systems and the Hyporheic Zone

The hydrology of a river with a matured series of beaver structures (ponds, canals, dams, food caches and lodges) is very different than a river with no or few beaver. Principles of healthy riverscapes require the river channel to be connected to the floodplain. Beavers create structures that add complexity to channels and force reconnection to the floodplain. Beaver dams help to combat incision in streams and to restore the natal geomorphology of degraded streams. The reduced energy of the flow causes less disturbance and makes the riverscape more stable. The ponded water caused by beaver activity vastly increases the volume of the hyporheic zone, an area of sediment and porous space under a stream bed where there is a mixing of groundwater and surface water. This sediment zone is critical to restoring chemical stability by filtering pollutants (especially nitrates) out of the stream for cleaner water. As the hyporheic zone cleans water through filtration, it also recharges groundwater. 

Beaver Support Carbon Storage

Beaver are essential to mitigating climate change because the wetlands that they create act as a natural carbon storage sink.22 As carbon storage continues to grow in importance to combat the climate crisis, protecting carbon sinks will be critical to expand climate resiliency. 

  • Productive wetlands restored for carbon sequestration quickly become net CO2 sinks with site level factors driving uptake variability. PLOS ONE, 16(3). 

  • Wohl, E. (2013). Landscape-scale carbon storage associated with Beaver Dams. Geophysical Research Letters, 40(14), 3631–3636. 

  • Johnson, R. R., Carothers, S. W., Finch, D. M., Kingsley, K. J., Stanley, J. T., Hamre, R. H., & Fouty, S. (2018). Euro-American beaver trapping and its long-term impact on drainage network form and function, water abundance, delivery, and system stability. In Riparian Research and management: Past, present, future. essay, United States Department of Agriculture, Forest Service, Rocky Mountain Research Station; 

  • Johnston, C. A. (2015). Fate of 150-year-old beaver ponds in the Laurentian Great Lakes Region. Wetlands, 35(5), 1013–1019. 

  • Johnston, C. A. (2019). 12. Beaver Wetlands. Wetland Habitats of North America, 161–172. 

  • Johnson, C. A. (2018). Beaver: Boreal Ecosystem Engineers. Springer International PU; 

  • Larsen, A., Larsen, J. R., & Lane, S. N. (2021). Dam builders and their works: Beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems. Earth-Science Reviews, 218, 103623.

  • Wegener, P., Covino, T., & Wohl, E. (2017). Beaver‐mediated lateral hydrologic connectivity, fluvial carbon and nutrient flux, and aquatic ecosystem metabolism. Water Resources Research, 53(6), 4606–4623.  

Beavers Restore Riverscapes Through Process-Based Restoration

  • Charnley, S., Gosnell, H., Davee, R., & Abrams, J. (2020). Ranchers and beavers: Understanding the human dimensions of beaver-related stream restoration on Western Rangelands. Rangeland Ecology & Management, 73(5), 712–723. 

  • Pilliod, D. S., Rohde, A. T., Charnley, S., Davee, R. R., Dunham, J. B., Gosnell, H., Grant, G. E., Hausner, M. B., Huntington, J. L., & Nash, C. (2017). Survey of beaver-related restoration practices in rangeland streams of the Western USA. Environmental Management, 61(1), 58–68. 

  • Pollock, M. M., Beechie, T. J., Wheaton, J. M., Jordan, C. E., Bouwes, N., Weber, N., & Volk, C. (2014). Using beaver dams to restore incised stream ecosystems. BioScience, 64(4), 279–290. 

  • Polvi, L. E., & Wohl, E. (2013). Biotic Drivers of Stream Planform: Implications for Understanding the Past and Restoring the Future. BioScience, 63(6), 439–452. 

Valuing Beavers Ecosystem Services

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