Expanding beaver populations may counteract climate-driven degradation of riverine water quality in the Western US.
Beaver dam on the East River at the Watershed Function SFA field site in Crested Butte, CO. Image courtesy of Christian Dewey.
The Science
Warming temperatures and frequent drought are degrading riverine water quality in the Western US. Simultaneously, climatic shifts and changes in ecosystem management are expanding the range of the American beaver, whose dams are known to improve riverine water quality. By comparing the water quality impacts of a beaver dam and historically low river levels, which likely represent river levels of a future (hotter) climate, we found that the beaver dam increased removal of reactive nitrogen, a freshwater contaminant, by 44% compared to low river levels. The beaver dam pushed an enormous volume of river water and reactive nitrogen into surrounding soils, where microbial processes converted reactive nitrogen to nitrogen gas, eliminating its potential as a freshwater contaminant and rendering it harmless.
The Impact
Researchers demonstrate that ecosystem feedbacks to climate change, such as the expansion of beaver populations, alongside ecosystem management practices, such as legal protections for beavers, can partially reverse the detrimental effects of climate change on water quality. By illustrating the interplay between beavers’ ecosystem services, climate change, and water quality, this research informs and supports land and ecosystem policies that aim to address water quality impacts of climate change.
Summary
Scientists monitored hydrologic and geochemical conditions along a reach of Colorado’s East River over multiple years (2018-2019), which captured a historic drought and the construction of a beaver dam at this site. Using these field measurements, they developed a reactive transport model to quantify dissolved oxygen and reactive nitrogen fluxes through riparian soils during the drought and construction of the beaver dam (2018), as well as during unusually wet conditions (2019). The model demonstrated that the beaver dam imposed hydraulic gradients across the riparian subsurface which were more than 10 times greater than the gradients imposed by low and high water conditions. By imposing a steep hydraulic gradient, the beaver dam increased the flux of water and nitrate into riparian soils (relative to the seasonal extremes), where microbial processes converted nitrate to nitrogen gas (denitrification). The overall increase in nitrate flux from the beaver dam led to a 44% increase in nitrate removal compared to seasonal extremes. Finally, researchers evaluated the beaver dam’s nitrate removal under a range of denitrification rates, finding that the relative effects of the dam were largely insensitive to the rates of microbial processes.
Contact
Christian Dewey
Stanford University
cwdewey@stanford.edu
Eoin L. Brodie, Watershed Function SFA LRM
Lawrence Berkeley National Laboratory
Funding
This work was supported by the Watershed Function Science Focus Area funded by the US Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research (BER); by the BER Environmental Systems Science Program; and by the DOE Office of Science Graduate Student Research Program.
Publications
Dewey. C. et al. “Beaver Dams Overshadow Climate Extremes in Controlling Riparian Hydrology and Water Quality.” Nature Communications, 13, 6509 (2022). [DOI: 10.1038/s41467-022-34022-0]
Related Links
Beavers will become a bigger boon to river water quality as U.S. West warms, Stanford study finds, Stanford News
Stanford University study explains how beaver activity may have long-term benefits on climate change, Bay Area ABC 7 News
How beavers could help protect water quality from climate change, Colorado Public Radio