B.J. Dittbrenner, University of Washington/Beavers Northwest

Beavers are both ecosystem engineers and keystone species. As ecosystem engineers, they modify their environment through dam building to create wetland systems which reduce their predation risk and increase growth of preferred food types. Their role as keystone species results from their ability to transform a stretch of single-thread stream into a large and wide wetland complex, with numerous pools of varying depths and temperature profiles, multiple braided channels at different heights, and piles of large woody debris. The rich complexity of these systems provide habitat for an amazing abundance and number of plant, insect, fish, amphibian, mammal, and bird species. Most beavers in the US were extirpated through over-trapping by the turn of the 20^th century. Only recently have we begun to see a resurgence of beaver populations and the ecological benefits they provide.

Supporting and encouraging this resurgence may become even more critical in the face of hydrologic shifts as a result of climate change. In 2009, the University of Washington’s Climate Impacts Group used climate models from the Intergovernmental Climate Impacts Group (ICCP) fourth assessment report (AR4) to produce downscaled models for the Pacific Northwest (PNW). These and subsequent models predict that the PNW will experience considerable hydrologic alterations over the next century. Summer precipitation and stream flow will likely decrease, as will snowpack; snow melt is projected to come earlier in the year, and winter precipitation, storm intensity, and stream temperatures will likely increase. These changes would threaten sensitive habitats and species. ESA-listed fish and wildlife, such as salmon and steelhead, will undoubtedly suffer additional declines in their already limited habitat if these projections are realized. Both hydrologic stability and ecosystem resilience will be substantially reduced by these changes.

As ecosystem engineers, beavers have the unique capacity to not only protect existing ecological function, but also buffer against future changes and habitat destruction. My primary research question is, therefore, can the return of beavers into these stream systems stabilize hydrology, retain water in streams during summer months, and increase ecosystem resilience?

Research Goals

Quantify the hydrologic benefit that beavers provide: how much water do beaver wetlands store, how do they supplement summer stream flow, and what is the effect on stream temperature?

Model these benefits across PNW streams to identify critical beaver population levels.

Education Goals

Provide educational opportunities and work experience to college students and recent graduates.

Community Goals

Establish multidisciplinary and multi-stakeholder partnerships with regional tribes, restoration organizations, and local jurisdictions.

Build a community of local cities and counties throughout the Puget Sound who recognize the importance of beavers in the landscape and adopt non-lethal beaver management programs.

A CREOi award in 2015 supported a full-time intern, covered research equipment expenses, scientific meeting expenses, and journal submission costs. The CREOi intern provided over 900 hours of assistance in monitoring and beaver trapping tasks. Through this assistance, 30 research sites were monitored, including 250 continuous temperature loggers, 300 ground water wells, 70 flow discharge locations, and 25 motion-activated cameras. In addition to our field data collection effort, we captured 78 beavers and were rewarded with substantial site modification and hydrologic alteration at 5 project sites after successful relocations. Initial field monitoring results from 2015 of are extremely promising. Successful relocation has created substantial storage of surface and groundwater, decrease in stream temperature, and increased habitat heterogeneity. Game cameras have documented an increase in biodiversity in the newly created wetland complexes. The data collection, beaver trapping and care, project coordination, and day-to-day operating tasks required for this project could not have been done without help from our intern and CREOi. ($20,000)