This case explores the Methow Beaver Project (MBP), an ambitious experiment to restore beaver (Castor canadensis) to a high mountain watershed in Washington State, USA. The Pacific Northwest is already experiencing weather regimes consistent with longer term climate projections, which predict longer and drier summers and stronger and wetter winter storms. Ironically, this combination makes imperative more water storage in one of the most heavily dammed regions in the nation. Although the positive role that beaver can play in watershed enhancement has been well known for decades, no project has previously attempted to re-introduce beaver on a watershed scale with a rigorous monitoring protocol designed to document improved water storage and temperature conditions needed for human uses and aquatic species. While the MBP has demonstrated that beaver can be re-introduced on a watershed scale, it has been much more difficult to scientifically demonstrate positive changes in water retention and stream temperature, given hydrologic complexity, unprecedented fire and floods, and the fact that beaver are highly mobile. This case study can help environmental studies students and natural resource policy professionals think about the broader challenges of diffuse, ecosystem services approaches to climate adaptation. Beaver-produced watershed improvements will remain difficult to quantify and verify, and thus will likely remain less attractive to water planners than conventional storage dams. But as climate conditions put additional pressure on such infrastructure, it is worth considering how beaver might be employed to augment watershed storage capacity, even if this capacity is likely to remain at least in part inscrutable.
Worldwide, climate change is producing historically novel hydrological conditions in watersheds that are essential to human and natural communities . Some areas, such as the Pacific Northwest of the United States, are experiencing both wetter winters and hotter and drier summers . This can result in significantly increased volatility in stream discharge, with higher maximum flows and lower minimum flows in the same river system . The challenge is to maximize retention and the slow release of clear, cool, water for sustained use, even as annual meteorological regimes become more extreme and variable. Although some water managers in the Pacific Northwest are calling for a new era of large-scale dam construction to address anticipated water shortages , the Methow Beaver Project (MBP) envisions another possibility: to restore beaver to as much of its former range as possible in local watersheds. Part of a network of so-called “beaver believers,” the MBP advocates using beaver to enhance watershed storage capacity while at the same time providing critical wetland habitat for fish and wildlife .
The broader context of the MBP is significant. Millions of people in the western United States rely on water stored as mountain snowpack for power, irrigation, and domestic uses. As the climate warms, more precipitation is falling as rain instead of snow, decreasing the depth and extent of mountain snowpack throughout the region in all but the highest montane elevations  (Figure 1).
This is alarming because in most of the western river basins, snowpack is a substantially larger component of water storage than human-constructed reservoirs . Compounding this trend, climate-induced seasonal shifts are changing the timing of mountain snowpack runoff, with already diminished snowpack melting earlier in the spring . Climate change is thus eroding a critical ecosystem service that people in the region once took for granted: the natural “water towers” (mountain snowpack) that collected and stored water in the winter and then delivered it downstream when most needed for irrigation and instream uses during hot summer months.
This development is exacerbated by two additional trends. First, changes to the region’s climate are exposing the west to more frequent extreme weather events, including both drought and flood . Longer summers with higher average temperatures and lower humidity make western forests more susceptible to wildfire, substantially altering forested watersheds. While fire has always played a crucial role in western forests, successional pathways are being upended, vegetation communities are transitioning higher in elevation and latitude, and more intense storms following more intense fires are increasing land slide events that accelerate soil loss and lengthen forest recovery time . Such storms also increase the speed and force of runoff, further incising stream channels and disturbing native fish spawning habitat.
Second, continued human population growth in the west is expected to put additional pressure on regional water resources, especially when water demand “hardens” as water transfers from agriculture to urban consumption reach their limits . During a severe drought, farmers can leave fields fallow or switch to less water-intensive crops. But urban dwellers who find their water taps dry will have few options. Both these trends point to the need for more water storage capacity in regional watersheds. Traditionally, this has meant building dams . Yet, new dam projects are likely to be extremely expensive and politically contentious, especially as many existing dams need environmental and safety retrofits or even de-commissioning . Extreme weather events also expose the vulnerabilities of existing infrastructure. A vivid reminder of this was the near-disaster at the Oroville Dam in Northern California in early 2017 . Water managers are increasingly recognizing that as the climate warms, large reservoirs will be more susceptible to large evaporation losses . For example, Lake Powell near Page, Arizona, loses an average of 860,000 acre feet of water  annually to evaporation and bank seepage. That amount is nearly three times Nevada’s annual allotment of Colorado River water . Several states, most notably Arizona, are exploring the potential for scaling up underground aquifer recharge and storage. Given the geographic diversity of the region, a diversity of storage options will be needed.
Restoring the storage capacity of the region’s higher-elevation watersheds is one such option. Temperatures are cooler at such elevations, resulting in less evaporation. And in many western watersheds, there is much that can be done to improve storage potential. Many of the region’s waterways were dramatically altered over the past 150 years by mining, grazing, logging, and roadbuilding, resulting in deeply incised waterways that are often disconnected from their original floodplain, which tends to hasten, not slow, runoff . In some cases, the U.S. Army Corps of Engineers even straightened river channels and removed riparian vegetation in the 1950s and 1960s with the aim of moving water more quickly down to reservoirs. Today, the consensus among water managers is just the opposite: as much water as possible should be retained high in the watershed for slow release downstream . In the Pacific Northwest, this is particularly important for native fish populations such as salmon and steelhead, which depend on higher elevation tributaries with cool and clean water to spawn . Stream ecologists argue that stream “complexity” with ample meander, abundant large wood, and extensive riparian vegetation is what is missing in many if not in most western rivers . This is the focus of many ongoing restoration projects . However, stream restoration can be very expensive. Using heavy equipment to re-introduce stream sinuosity and re-creating wetlands with the aim of storing and cooling water is challenging. Restoration project design and implementation often takes years to complete, impacting few stream reaches.
These problems have water managers looking for alternative tools to enhance watershed storage capacity, and one such tool is reintroducing the North American beaver, Castor canadensis, to western watersheds. Beaver are noted for its capacity to transform the landscapes they inhabit  (Figure 2).
Beaver build dams to transform shallow streams into ponds or wetlands deep enough to provide safe underwater access to bankside forage adjacent to their lodges, because they are quite vulnerable to predation when not in the water. On average, beaver dams are <50 m long and 2 m tall  (Figure 3).
Beaver ponds and associated wetlands have the capacity to store a surprising amount of water. One study in Washington State noted that on average, each beaver dam impounds 3.5 acre feet  of surface water, with an additional three to five times as much stored as associated groundwater . Groundwater flow, also known as hyporheic exchange, delivers water back to the stream below the beaver dam and is particularly important in the context of climate change . Cooled to match the surrounding constant ground temperature (~50°F), this water is released slowly, akin to a sponge dripping water . Underground water is much less susceptible to the evaporation problems of exposed surface water in large, man-made reservoirs. But it is difficult to measure hyporheic groundwater storage and flow with precision, and yet these data are essential for water planners and regulators to make fully informed decisions (Figure 4).
Before European settlement, beaver were ubiquitous across their range in most of North America. Studies show that there may have been nearly half a billion beaver across the continent, with an average of one beaver dam for each half mile of stream . By the mid of 19th century; however, beaver were nearly extirpated by trappers for their pelts, which were shipped to Europe to make fashionable felt hats. From 1750 to 1850, beaver pelts were the de facto currency across much of the North American frontier, and beaver were even hunted to extinction in some areas as trappers intentionally created “fur deserts” to limit expansion of new colonists on to previously claimed territory . The impact of historic beaver eradication on watersheds should not be underestimated. Without beaver to maintain the dams, streams unraveled, down-cutting and moving water and sediments quickly downstream, losing much of their prior storage capacity. Hydrologists argue that our very conception of streams as a continuum of unimpeded flow is not based on what streams naturally were, but rather what we made them by eradicating beaver . Restoring watersheds with beaver thus requires re-imagining streams as discontinuous, with beaver dams serving as “speed bumps,” slowing water and trapping sediment during high flow events. The MBP is an effort to facilitate and document what this re-imagination of western watersheds might look like in the context of expected climate challenges.
The Methow Valley is situated on the east side of the Cascade Mountains in northern Washington State. With a watershed of 1,825 square miles, the Methow River flows from its headwaters in the north Cascades 80 miles to its confluence with the Columbia River. Being home to 5,000 people, the valley is supported by both an amenity and agricultural economy (Figure 5).
In 2000, US Forest Service wildlife biologist John Rohrer was looking through Forest Service archives and noticed a 1932 map showing 61 beaver relocation sites in the Methow Valley. The timing was fortuitous: 2000 was also the year the Washington State Legislature banned body-gripping animal traps statewide, meaning that it would be much more difficult to remove beaver once established in streams . Indeed, the Methow watershed had perhaps only 10–15% of the beaver it could theoretically support. At the same time, the Washington State Department of Fish and Wildlife was removing “nuisance” beaver in the lower reaches of the Methow, where beaver were plugging road culverts, cutting down trees near vacation homes, blocking irrigation ditches, and cutting down orchard trees. Rohrer’s original insight was to see a solution in a problem: re-locate “nuisance” beaver causing problems low in the watershed (where they are often “bank beaver” that do not need to build dams) to suitable habitat on public lands, high in the watershed where beaver need to block streams to create good escape habitat and thus play a more substantial role as a keystone species and ecosystem engineer. Over the next several years, Rohrer and his colleagues re-located 18 beaver with mixed success. On Bear Mountain Creek, a narrow stream became a 23-acre complex of dams and wet meadows. But many of the re-located beaver failed to establish new dams and lodges or simply disappeared, likely victims of predation .
In 2006, the Washington State Department of Ecology became interested in the beaver re-locations as a possible way to lower area stream temperatures, which were often in violation of Clean Water Act standards, and creating toxic conditions for migrating salmon and steelhead. How might beaver re-locations be scaled up to make a significant difference in stream temperature and late-season flow for fish? Over the next 2 years a collaborative team including staff from the US Forest Service, the Washington Department of Fish and Wildlife, The Methow Conservancy, and the US Fish and Wildlife Service – Winthrop National Fish Hatchery developed a 10-year plan to establish beaver in 50 locations throughout the Methow watershed . Establishing new beaver colonies, however, is not as simple as catching them in one place and releasing them in another place. On average only 20% of re-locations in the western US were successful . It was clear that the MBP would need to improve on those odds to meet its goal. Working as a collaborative team, the project developed a plan with four key elements.
Habitat Suitability Analysis
Using GIS spatial mapping technology and on-the-ground verification, the team identified sites in the Okanagan National Forest most likely to sustain a new beaver colony: a stream gradient preferably <3% with moderate flows, abundant aspen and willow for forage and dam/lodge building, a wide floodplain with silty substrate, a good supply of herbaceous forage, and minimal impacts from livestock. Based on these evaluations, the collaborative team determined that there are plenty of places in the national forest where beaver could thrive and create vast wetland complexes  (Figure 6).
Intake and Pairing Facility
The next step was to assist landowners who wanted beaver removed from their property. Once the beaver were trapped and removed, they needed a place to stay before they are re-located up in the national forest. A holding pen was established at the Winthrop National Fish Hatchery, and it soon became much more than a holding facility. Wildlife biologists know that beaver are social, not solitary creatures. The challenge for the MBP was to devise a way to help beaver, which are frequently caught independently at separate locations, pair up before releasing them into the wild, reasoning that an established pair would be more likely to make a new home at the relocation site. One key challenge was to determine the sex of the captured beaver, which was not easy because beaver have internal reproductive organs and genital openings are difficult to discern. After working with several expensive options, the team found a low-tech innovation: a simple nylon funnel bag that immobilizes the beaver without anesthesia, allowing easy examination of sex-specific oil gland secretions and safety for both the beaver and the human handlers. Potential beaver mates are then placed in large holding pens where they can freely select their mates  (Figures 7–9).
Tracking and Monitoring Protocol
Each beaver was fitted with a passive integrated transponder (PIT) tag in its tail, so that the team could identify individuals and track the beaver’s movement. Ideally, beaver stay where they are released and begin building dams and lodges. To promote this, the team builds a temporary shelter for the beaver before they arrive. From this refuge beaver have the best chance to evade predators, such as mountain lions, wolves, bobcats, bears, and coyotes. Crews visit release sites weekly for 4 weeks, then semi-monthly for the remainder of the season, using the PIT tags to track beaver locations. If at least one new dam is constructed that at least doubles the stream cross section (depth × width), and that dam persists for at least a year, the site is deemed successful. If the site is unsuccessful, the PIT tags allow researchers to track the movement of the beaver, which can sometimes travel long distances. Highly suitable sites are often re-tried multiple times and frequently subsequent releases are successful. The project has documented success rates of nearly 50%. This is only possible with persistent tracking and monitoring .
Stream Temperature and Flow Study
Although there is ample anecdotal evidence documenting the benefits of beaver dams for water retention, stream temperature moderation, riparian expansion, and sediment retention , the MBP launched rigorous stream temperature and flow studies on a watershed-level scale, which had not been attempted to date. The plan, implemented in June 2011, called for gathering temperature and flow information at designated sites for 3 years before beaver reintroduction to establish baseline conditions, then 3–5 years of data after beaver reintroduction at the same sites. The MBP argued that this information could demonstrate to water planners and managers that an ecosystem services approach, centred on beaver restoration in upper watersheds, could substantially contribute to expected water storage needs  (Figure 10).
RESULTS AND ANALYSIS
The MBP has demonstrated that it is possible, on a watershed scale, to carefully plan, implement, and monitor beaver reintroduction (Figure 11). A cooperative and integrated approach was essential to this success. Landowners, federal and state agencies, and larger communities of interest must be the willing partners for the success of a project of this scale (Supplementary Material). The project also demonstrated that careful attention to beaver pairing greatly increases the likelihood of successful colony establishment. With more beaver on the landscape, there is visual evidence of resulting wetland enhancements (Figure 12).
But it has been much more difficult for the MBP to demonstrate streamflow and temperature benefits on a wider watershed scale. They encountered several problems. First, pinpointing beaver dam complexes as the cause of lower stream temperatures is challenging even on a localized scale, and still more difficult and complex on a watershed scale. Much of the water cooled by beaver dams filters back into the stream below the dam as groundwater. Emergence of downstream groundwater can be “patchy,” depending on local geologic conditions, thus difficult to measure reliably . Further, unless multiple beaver dam complexes dominate stream reaches, it is possible that improvements in temperature and flow may be too small to measure given other variables, such as weather or variation in precipitation.
Second, the MBP’s monitoring program suggests that beaver are considerably more mobile than previously known . In a sense, this new knowledge is a successful outcome of this project, but beaver’s mobility makes long-term, longitudinal studies of watershed conditions quite difficult. If beaver tend to their dams in some years then alternately ignore them, as it appears for some of the MBP sites, it is difficult to measure and verify temperature and flow conditions over time and reliably attribute them to beaver activities. The MBP is continuing to narrow down optimal conditions that encourage beaver to remain in one place for an extended period, but beaver are wild animals and some measure of unpredictability will always remain.
Third, a significant goal of the MBP is to show that restoring beaver can help watersheds adapt to novel watershed conditions as the climate warms, yet, ironically, these same conditions make it nearly impossible to rigorously document on-the-ground results of the restoration efforts. The forests in the Methow Valley experienced two seasons of unprecedented mega-fires in 2014 and 2015, followed by extreme storms that caused widespread flooding and mudflows, wiping out nearly all MBP monitoring instruments, forcing the MBP to abandon its streamflow study (Figures 13 and 14).
Still, many beaver complexes survived the fires, and beaver are repairing damaged dams and re-colonizing burned areas. These dams and surrounding wetlands help trap runoff sediment and provide crucial sources of water for wildlife  (Figure 15).
New technologies and research may help the MBP better document water retention behind beaver dams. One such technology combines Google Earth and ortho-rectified drone images for better visualization of beaver ponds amid dense vegetation (Figure 16).
Another promising area of research is “beaver mimicry,” where researchers construct and maintain “beaver dam analogues,” carefully measuring before and after water temperature and groundwater storage conditions in the affected area . From these data, it may be possible to develop generalized temperature data and storage models and estimates, but again, much depends on local geologic conditions so there is no universal model or solution. But precision may be less important than a general sense of how beaver can help watersheds. MBP is currently working with a Michigan limnology firm to estimate, using conservative infiltration studies from Pollock and others , that over 200 million gallons of water are stored underground in beaver sites established by the project to date .
Several environmental groups refer to beaver restoration as a “solution” to climate-induced water storage problems . A Sierra Club article, for example, suggested that the dams of just 40 million beaver would store enough surface and groundwater to meet the water needs of the United States in all sectors (129.6 trillion gallons) in 2010 . But there is little evidence to suggest that so many beaver would be welcome. Already, Wildlife Services (US Department of Agriculture) exterminates over 21,000 “nuisance” beaver annually . Too much of its habitat has been altered or occupied by human uses. But the MTB has demonstrated that there are likely many places, high in western watersheds, where few such conflicts exist, and there may be still more places where people could quite productively co-exist with these industrious rodents if the benefits were more widely known and if public assistance is available when problems arise.
Members of the MBP staked part of their work on the hope that they could fully document the hydrological effects of beaver on a watershed scale. This effort was mostly met with setbacks. But their highly successful beaver re-location program continues. There is simply no evidence that beaver harm watershed storage capacity, and a wealth of evidence that beaver wetlands act as watershed sponges, storing water for later season release. MBP members conceptualize their efforts as working with, rather than against nature, resisting the temptation to solve all problems with expensive and highly engineered infrastructure projects. This does not mean that large infrastructure projects are bad, but rather, that more nature-friendly alternatives may exist if one pays attention to local opportunities to enhance ecosystem services. In Seeing Like a State, political anthropologist James Scott shows how large and highly engineered infrastructure projects preferred by state planners often have devastating consequences because planners failed to consider local knowledge and conditions . Although climate change is a global phenomenon, climate adaptation and ecosystem services happen mostly at the local level, so local knowledge of opportunities will be essential. Members of the MBP saw a way to improve their watershed while at the same time helping downstream landowners cope with nuisance beaver. Working with the beaver over the years, they also found inspiration in the beaver themselves. Although their wild nature made it difficult for this project to produce long-term measurable results, they celebrate each new beaver pond and frequently invite groups to observe the beaver successes. Wildlife biologists and ecologists marvel at the persistence and industriousness of the beaver, and how beaver, in making a home for themselves, create large wetlands that are crucial for an abundance of other species . Perhaps one lesson from this case is that human and natural communities, when working together, can both persist and thrive in the coming era of climate change, in ways both seen and unseen (Figure 17).
CASE STUDY QUESTIONS
How are watersheds across the American West challenged by expected changes in climate in the coming 50–100 years? How will these changes affect agricultural and municipal water supplies? What is the source of the water you use? How will expected changes in climate in your area affect your water supply?
Refer to Figure 1. If the climate is warming, why are there still some mountainous areas that may receive more snowpack, even as the general trend is for less snowpack region-wide? What does this tell us about the complexity of watersheds in the context of climate change, and what adaptive approaches might be considered? Think of the advantages and disadvantages of diffuse and centralized approaches.
“Beaver believers” suggest that a diffuse, ecosystem services approach to expected future water needs holds much promise, but as this case demonstrates, these services can also be difficult to quantify and verify. Why? How might water planners and regulators consider these potential services when formulating planning documents for political decisions and public investments? Or are these potential services simply too speculative for such purposes?
Beaver can sometimes be difficult to live with when they cut down trees, dam culverts, or flood roadways. In many states, it is not illegal to shoot and kill beaver. At the same time, the ecosystem services value (water storage, sediment retention, and habitat enhancement) for each beaver is approximately US$1,750 according to a study done by ECONorthwest . How should the needs of landowners be balanced with the public’s interest in preserving ecosystem services? From what you have learned in this case, how can conflicts with private landowners be either avoided or managed?
How does the MBP illustrate both the advantages and disadvantages of ecosystem services-based approaches to the challenges of climate adaptation? Compare with the advantages and disadvantages of conventional water infrastructure projects.
Some climate activists suggest that we should focus almost exclusively on climate mitigation by radically reducing greenhouse gas emissions; adaptation is like trying to mop up an overflowing bathtub before turning off the faucet. Yet turning off that faucet is a daunting proposition. Can relatively small climate adaptation efforts such as the MBP contribute to the larger effort to build public recognition of climate challenges and perhaps greater political will for climate mitigation? Explain why or why not.
Both the authors contributed equally to the conception, drafting, revision, and analysis of this case study, and have approved the final version.
The authors wish to thank the Methow Beaver Project for providing figures and photographs.
Authors declare no conflicts of interest.
Appendix A: Methow Beaver project partners and supporters.
ADDITIONAL TEACHING RESOURCES
Video: Beaver: back to the Future. Produced by the Grand Canyon Trust. Available: https://www.youtube.com/watch?v=_23vuRU2Ews.
Video: One stick at a time. Produced by the Ten Decades Project. Available: https://www.youtube.com/watch?v=EQNK7W-P-_0.