A beaver and the Gallatin Range, courtesy of Yellowstone National Park Service.
Beavers (Castor canadensis), the hardworking (and often under-appreciated) ecosystem engineers are helping restoration practitioners to make the most of limited resources to restore stream function. Through their persistence, beavers create - and better yet, maintain - disturbance-resistant landscapes that enhance biodiversity, improve water quality, reduce damage from wildfire, droughts, flooding, and more. These ecosystem services provide on the order of $69,000 per square kilometer, per year of benefits (Jordan and Fairfax 2022).
We are showcasing the work of beavers, as well as beaver-inspired watershed restoration efforts, to combat the evolving challenge of incorporating climate change considerations and methods that will be resilient to or mitigate climate change. These include a multi-phased project on Whychus Creek in the Deschutes River Basin of Central Oregon, the return and enhancement of wet meadows for vulnerable birds in Wyoming, and a pasture irrigation project in Utah.
Beavers & Beaver Restoration Techniques
From our 21st century vantage, it's hard to conceive how profoundly beavers shaped the landscape. Surveying the Missouri River Basin in 1805, the explorers Meriwether Lewis and William Clark encountered beaver dams "extending as far up those streams as [we] could discover them." Their networks of dams and ponds once puddled the continent — impounding enough water to submerge Washington, Oregon, and California. Beavers were historically present from northern Mexico up to the southern fringe of the tundra on the Arctic coastal plain in Alaska and northern Canada. The sheer extent of their habitat and size of their population had a huge effect on landscapes across the US, and elsewhere, maintaining the wide, beaver stream-wetland valleys that shaped waterways throughout their range. In a healthy, beaver-rich creek, dams slow water flows, capture sediment, recharge shallow groundwater, cool stream flows, provide flows longer into dry seasons, support wet, healthy riparian corridors, and the list goes on.
Once numbering upwards of 250 million in North America (Wohl 2021, Atwater 1996), beavers could not withstand the fur trappers who arrived in New England in the 17th century, then quickly spread west. By 1843, naturalist John James Audubon found the Missouri Basin "quite destitute." At the outset of the 20th century, researchers estimate just 100,000 beavers survived — less than one tenth of 1% of historic numbers (Wohl 2021). Until recently, beavers who found themselves on private land were even considered predators in Oregon and elsewhere, and could be killed with little or no regulation.
We are showcasing the work of beavers, as well as beaver-inspired watershed restoration efforts, to combat the evolving challenge of incorporating climate change considerations and methods that will be resilient to or mitigate climate change. These include a multi-phased project on Whychus Creek in the Deschutes River Basin of Central Oregon, the return and enhancement of wet meadows for vulnerable birds in Wyoming, and a pasture irrigation project in Utah.
Beavers & Beaver Restoration Techniques
From our 21st century vantage, it's hard to conceive how profoundly beavers shaped the landscape. Surveying the Missouri River Basin in 1805, the explorers Meriwether Lewis and William Clark encountered beaver dams "extending as far up those streams as [we] could discover them." Their networks of dams and ponds once puddled the continent — impounding enough water to submerge Washington, Oregon, and California. Beavers were historically present from northern Mexico up to the southern fringe of the tundra on the Arctic coastal plain in Alaska and northern Canada. The sheer extent of their habitat and size of their population had a huge effect on landscapes across the US, and elsewhere, maintaining the wide, beaver stream-wetland valleys that shaped waterways throughout their range. In a healthy, beaver-rich creek, dams slow water flows, capture sediment, recharge shallow groundwater, cool stream flows, provide flows longer into dry seasons, support wet, healthy riparian corridors, and the list goes on.
Once numbering upwards of 250 million in North America (Wohl 2021, Atwater 1996), beavers could not withstand the fur trappers who arrived in New England in the 17th century, then quickly spread west. By 1843, naturalist John James Audubon found the Missouri Basin "quite destitute." At the outset of the 20th century, researchers estimate just 100,000 beavers survived — less than one tenth of 1% of historic numbers (Wohl 2021). Until recently, beavers who found themselves on private land were even considered predators in Oregon and elsewhere, and could be killed with little or no regulation.
In a relatively short span of time, the mosaic of habitats that beaver had created and maintained were unraveling. With the loss of beaver, old dams collapsed and washed away, streams eroded into their beds, cutting deep gullies (in a process called incision) and impacting the hydrology of the entire oncewetted floodplain valley. These steep-sided, incised streams lost the ability to spill onto their floodplains and recharge aquifers. As a result, groundwater levels and surface water flows greatly decreased. Wetlands dried up. Some groundwater-fed streams dried up altogether. This had a huge and lasting effect on not only the salmon and trout that reared in their pools, but many, many flora and fauna that benefited from the beavers' hard work.
Fast forward to current times, and beavers’ numbers are rebounding. Their ecological engineering prowess is much more appreciated, and a notable effort is underway to create the conditions that beavers need to sustain in an area. In effect, we are working on re-beavering streams.
Fast forward to current times, and beavers’ numbers are rebounding. Their ecological engineering prowess is much more appreciated, and a notable effort is underway to create the conditions that beavers need to sustain in an area. In effect, we are working on re-beavering streams.
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One solution is a rodent-human collaboration. This encompasses techniques that either mimic the beaver dams and their influence on channels, such as building small dams with posts and woven willow lattices; or projects that create conditions that can support a beaver recolonization to lure our friends back into their habitat, such as planting the tastiest plants, providing security and the appropriate amount of space.
These approaches go by many names, for example, Beaver Dam Analogs (BDAs) and Post-Assisted Log Structures (PALS), and BeaverHoods (Jacobs 2021). They mostly refer to projects whose goals include slowing down creek flows, spreading water onto floodplains, creating hydrologic, sediment and plant variability, and rewetting habitats in hopes that beaver nearby return to the valley and take over, gnawing down nearby trees and reinforcing the dam with branches and mud. Perhaps for now we can call them beaver-motivated projects. |
Incised stream in Browns Canyon pre-BDA restoration.
Image from Utah Department of Natural Resources. |
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The benefits of beaver on the landscape are many! The dams store water during wet periods, spreading the water onto the floodplain and into shallow groundwater storage (Dittbrenner et al. 2022). These dynamics increase streamflow during summer (Puttock et al. 2021), reduce flooding during wet months (Muhawenimana et al. 2023), reduce wildfire impact (Fairfax) and improve the riparian and floodplain corridors (Larsen et al. 2021). All these, in turn, support the recovery of our native fishes.
This restoration approach is being used to heal the incised streams, disconnected wetlands and floodplains across the landscape. The technique has quickly gained fanfare from many practitioners. |
Federal agencies, nonprofits, and even private ranchers have installed the structures to return life to deeply eroded streams and, in some cases, to help re-establish beavers in long-abandoned territories. In Wyoming, BDAs are creating wet meadows for a vulnerable bird species. In Oregon, they're rebuilding salmon streams. In Utah, they're helping irrigate pastures for cattle. The projects are many, successful and encouraging.
Part of the allure is also that these methods are cheap compared with other restoration techniques. The costs typically amount to materials for the posts, since many projects rely on volunteer sweat equity. Once these types of projects are installed, the beavers themselves become reliable, hard-working volunteers we can count on to carry the project forward.
Despite the fanfare, the movement to restore nature’s best river restoration engineers has sometimes experienced growing pains. Some landowners and government agencies are loath to aid a rodent infamous for felling valuable trees, flooding property, and clogging road culverts. In 2022 alone, the U.S. Department of Agriculture (USDA) killed more than 23,000 beavers deemed to be nuisances (USDA 2017). As successful projects improve year after year, and the skeptics turn to proponents, beaver-motivated projects are gaining traction. There are obvious areas where this approach will not work, where the messiness and flooding associated with a growing beaver dam will cause conflict. Other solutions are needed there. But where there is room and conditions to support beaver, these techniques can have beautiful benefits for a fraction of the cost. We highlight some specific projects next.
Part of the allure is also that these methods are cheap compared with other restoration techniques. The costs typically amount to materials for the posts, since many projects rely on volunteer sweat equity. Once these types of projects are installed, the beavers themselves become reliable, hard-working volunteers we can count on to carry the project forward.
Despite the fanfare, the movement to restore nature’s best river restoration engineers has sometimes experienced growing pains. Some landowners and government agencies are loath to aid a rodent infamous for felling valuable trees, flooding property, and clogging road culverts. In 2022 alone, the U.S. Department of Agriculture (USDA) killed more than 23,000 beavers deemed to be nuisances (USDA 2017). As successful projects improve year after year, and the skeptics turn to proponents, beaver-motivated projects are gaining traction. There are obvious areas where this approach will not work, where the messiness and flooding associated with a growing beaver dam will cause conflict. Other solutions are needed there. But where there is room and conditions to support beaver, these techniques can have beautiful benefits for a fraction of the cost. We highlight some specific projects next.
Process-Based Restoration
On the light-handed and relatively economic end of the restoration spectrum, process-based restoration focuses on creating conditions that allow nature to heal itself, rather than relying heavily on human intervention. The concept recognizes that to restore ecologically functional habitats, we need to restore the physical and ecological processes responsible for creating and maintaining those conditions, often just by removing human-caused constraints. In short, giving the habitats and wildlife within them the space they need to function as they should and “letting the system do the work”.
On the light-handed and relatively economic end of the restoration spectrum, process-based restoration focuses on creating conditions that allow nature to heal itself, rather than relying heavily on human intervention. The concept recognizes that to restore ecologically functional habitats, we need to restore the physical and ecological processes responsible for creating and maintaining those conditions, often just by removing human-caused constraints. In short, giving the habitats and wildlife within them the space they need to function as they should and “letting the system do the work”.
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Stream and riverine landscapes are made up of a series of interconnected floodplain, groundwater, and channel habitats, and their associated biotic communities. Keeping the connections among them is vital for healthy aquatic systems. Dam removal is an excellent method for restoring many river systems, but it does not always take something as hefty as removing a dam to restore natural processes.
Other project examples of restoring processes include improving undersized road crossings, where dams and pipes can impact miles of precious habitat with a relatively small effort. So can removing constraints along the edges of a channel - levees, dikes and impinging infrastructure. |
The restored Elwha river flowing freely in the Olympic Peninsula. Photo by Richard Probst.
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These actions restore the natural hydrology, while in the process allow for a variety of habitat types, including the restoration of wetlands (aka nature’s sponge), to the restoration of estuaries (a much underappreciated habitat type), to protection of the uppermost parts of the watershed: the headwaters, and a focus on conservation efforts such as the proposed new Oregon Wild and Scenic Rivers legislation. In essence, just removing hard barriers to let the river’s processes do their thing.
It’s worth noting the diversity of landscapes on which similar approaches can be applied. We will touch back on this through our case studies, but the approach to restoring a high desert system compared with a coastal system, or estuarine versus headwater, may not be as different as one might initially think. Many groups are making methods and materials accessible, driving the science and implementation of these relatively inexpensive projects, and working with an array of landowners to create tools and shared knowledge to get more done.
As mentioned in the spring 2023 issue of Free Flow, how we approach river restoration has evolved over time. When the restoration practice began, projects involved engineering-heavy, precise and stable approaches. As we learned more, the approaches evolved to focus on the restoration of processes by removing the constraints impinging the channel, and as much as necessary, letting the channel dictate its own recovery. Hard engineering is necessary in some settings, and in many cases there is not enough space to work with, but when there is, it can be magical to just free the river and watch it evolve and heal itself. You know the phrase “Free the heels (or the reel) and the soul will follow”? Well, something just like that.
Restoration of critical processes also allows the system to respond to future perturbations (including and especially climate change impacts), enabling riverine ecosystems to evolve and continue to function in response to shifting system drivers (e.g., changes in sediment load, hydrology, or riparian vegetation, etc). It relies on the understanding that natural systems have inherent resilience and the ability to self-regulate if given the opportunity.
One of the main characters in these restoration stories is the beaver. In the case studies outlined at the link below, we will see examples of techniques that focus on creating ideal conditions for beavers to thrive and let the beavers do the hard work, and finally stories of process-based restoration Implementation. All in the hopes of a little affirmative action for our ecosystem engineers in support of the recovery of our native fishes.
It’s worth noting the diversity of landscapes on which similar approaches can be applied. We will touch back on this through our case studies, but the approach to restoring a high desert system compared with a coastal system, or estuarine versus headwater, may not be as different as one might initially think. Many groups are making methods and materials accessible, driving the science and implementation of these relatively inexpensive projects, and working with an array of landowners to create tools and shared knowledge to get more done.
As mentioned in the spring 2023 issue of Free Flow, how we approach river restoration has evolved over time. When the restoration practice began, projects involved engineering-heavy, precise and stable approaches. As we learned more, the approaches evolved to focus on the restoration of processes by removing the constraints impinging the channel, and as much as necessary, letting the channel dictate its own recovery. Hard engineering is necessary in some settings, and in many cases there is not enough space to work with, but when there is, it can be magical to just free the river and watch it evolve and heal itself. You know the phrase “Free the heels (or the reel) and the soul will follow”? Well, something just like that.
Restoration of critical processes also allows the system to respond to future perturbations (including and especially climate change impacts), enabling riverine ecosystems to evolve and continue to function in response to shifting system drivers (e.g., changes in sediment load, hydrology, or riparian vegetation, etc). It relies on the understanding that natural systems have inherent resilience and the ability to self-regulate if given the opportunity.
One of the main characters in these restoration stories is the beaver. In the case studies outlined at the link below, we will see examples of techniques that focus on creating ideal conditions for beavers to thrive and let the beavers do the hard work, and finally stories of process-based restoration Implementation. All in the hopes of a little affirmative action for our ecosystem engineers in support of the recovery of our native fishes.
CASE STUDIES:
Birch Creek, Southeast Idaho Some ranchers have also embraced beaver-based restoration. A rancher named Jay Wilde from Mink Creek, Idaho spent years trying to restore perennial flow to Birch Creek, a seasonal stream on his land. He grew up swimming and fishing in Birch Creek all summer long. But when Wilde took over the family farm from his parents in 1995, the stream was dry by mid-June. He realized this was partly because his family and neighbors, like generations of American settlers before them, had trapped and removed most of the dam-building beavers. The settlers also built roads, cut trees, mined streams, overgrazed livestock and created flood-control and irrigation structures, all of which changed the plumbing of watersheds like Birch Creek’s. Wilde then tried numerous ways to improve stream conditions, but it wasn't until he incorporated beavers that he saw results. In 2015, he invited scientists to build 19 BDAs on the creek and release five beavers nearby. The following summer, the stream stayed wet for two months longer than usual, helping to irrigate his grazing meadows. In just three years, those beavers built 149 dams, transforming the once narrow strip of green along the stream into a wide, vibrant floodplain. Birch Creek flowed for 42 days longer, through the hottest part of the summer. Fish rebounded quickly too: Native Bonneville cutthroat trout populations were up to 50 times as abundant in the ponded sections in 2019 as they were when surveyed by the U.S. Forest Service in 2000, before beavers went to work. |
Bridge Creek, Eastern Oregon Central Oregon's Bridge Creek, a 45-kilometer-long tributary to the John Day River, is an extensive BDA test project that started implementation in 2009, over 14 years ago. There is a long and storied history of beaver removal at the site: in the 1820s, English trappers deliberately exterminated the region's beavers to dissuade U.S. trappers from invading the Oregon Territory, which was claimed at the time by both the United Kingdom and the United States. The gambit failed, but the beavers' destruction, combined with unchecked cattle grazing, have left an enduring legacy. Without the beaver dams to slow the flow and encourage sediment deposition, Bridge Creek devolved into a narrow trench bordered by dried out pastures. Despite its grim appearance, Bridge Creek continued to support a small population of endangered steelhead— rainbow trout that, like salmon, migrate to the ocean and back. A skeleton crew of beavers had also survived, although any dams they built across the sluice-like channel tended to wash out during bigger storms. In the mid-2000’s, scientists had been documenting the amounts of sediment trapped behind beaver dams and thought that creating those conditions in Bridge Creek could have a profound benefit on the degraded channel, reconnect it with the floodplain, and inundate side channels and backwaters in which juvenile steelhead could thrive. In 2009, a hydraulic post-pounder was used to build 76 BDAs, built to mimic the function of natural beaver dams with on-site building materials (such as wood, turf, mud, and cobble), and can be reinforced with wooden posts. Beavers soon returned to the site and went to work. By 2013, monitoring showed that beavers had fortified nearly 60 of the BDAs and built 115 new dams (Silverman et al. 2019). This combination of constructed and natural beaver dams can create widespread benefits at relative low-cost per area restored (Bouwes et al. 2016; Weber et al. 2017). The overarching goal was to convert a drastically simplified stream into a complex one. With the brilliant, natural ecological engineers at work, their dams slowed the water, and the stream bed began climbing out of its trench, spilling water onto floodplains. The creek's submerged area tripled, and side channels grew by more than 1,200% in just a matter of a few years. Steelhead soon took advantage of the renewed habitat. Bridge Creek produced nearly three times more fish than a nearby control stream, and its young steelhead were 52% more likely to survive, the researchers reported in 2016 in Scientific Reports (Bowes et al.). Other studies found the dams and ponds actually helped moderate water temperature spikes, by allowing water to percolate through the gravel and streambed sediment. Projects like this, with nearly 10 years of monitoring, are incredibly valuable. Lessons learned along the way will inform efforts and decisions on subsequent projects and provide optimism that inexpensive efforts can have big impacts, and reverse declines that lasted decades. |
Whychus Creek, Central Oregon Why restore Whychus Creek? Historically, Whychus Creek was a mixture of narrow canyon stretches and stretches with broad, well vegetated meadows where the creek could spill over its banks. The biological importance of these large meadows was significant, especially considering all of the arid land surrounding them. The meadows provided diverse stream and side channel habitats for fish to spawn, rear, and hide. Streamside vegetation provided cover for wildlife and helped maintain cool stream waters. Nearby wetlands and bends in the creeks, called oxbows, were home to amphibians and songbirds. Only a small portion of the total length of Whychus Creek can provide this critical meadow habitat. Willow Springs Preserve is one of these special sections. Today, this portion of Whychus Creek is disconnected from its surrounding meadow. Habitat within and along the creek is very basic, lacking the diversity that fish and wildlife need to thrive. Fortunately, the creek has not cut down so deep into its channel that it cannot move from its current position. In fact, the creek is already starting to elbow its way out of its main channel in several parts of the Preserve, creating new meanders. Ultimately, the goal is to help return the creek to a healthy, biologically diverse condition and resilient condition capable of maintaining a diverse and self-sustaining set of fluvial and riparian processes that benefit an abundance of aquatic and terrestrial fish and wildlife species. How is Whychus Creek being restored? Instead of implementing restoration using large equipment to reshape the channel and surrounding floodplain, a much less invasive method is being employed. A small crew of young adults worked to install hand-built wood PAL and BDA structures. These structures were installed in the stream channel and in the adjacent floodplain. A highlight of this and similar projects is that they reduce design and implementation costs and allow natural stream processes to do much of the restoration “work.” This minimizes economic and ecological risks associated with stream restoration implementation. A win-win-win. |
REFERENCES:
Annegret Larsen, Joshua R. Larsen, Stuart N. Lane. 2021. Dam builders and their works: Beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems. Earth-Science Reviews, Volume 218, 2021, 103623, ISSN 0012-8252, https://doi.org/10.1016/j.earscirev.2021.103623.
Atwater, Alice. 1996. Water: A Natural History. Published by Basic Books. 224 pages.
Castro, Janine & Pollock, Michael & Jordan, Chris & Lewallen, Gregory & Woodruff, Kent. 2017. The Beaver Restoration Guidebook Working with Beaver to Restore Streams, Wetlands, and Floodplains. Prepared by US Fish and Wildlife Service North Pacific Landscape Conservation Cooperative.
Dittbrenner, Benjamin J., Schilling, Jason W., Torgersen, Christian E., and Lawler, Joshua J. 2022. Relocated Beaver Can Increase Water Storage and Decrease Stream Temperature in Headwater Streams. Ecosphere 13(7): e4168. https://doi.org/10.1002/ecs2.4168
Jacobs, Jefferson. 2021. BeaverHOODS: A customizable conceptual model for guiding beaver ecology, education, reach-scale restoration implementation, and watershed-scale restoration strategies. Conference presentation: River Restoration Northwest Speaker Series. doi: 10.13140/RG.2.2.30563.27686.
Muhawenimana, V., Follett, E., Maddock, I., Wilson, C. 2023. Field-based monitoring of instream leaky barrier backwater and storage during storm events. Journal of Hydrology, Volume 622, Part A. 129744, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2023.129744.
Puttock, A, Graham, HA, Ashe, J, Luscombe, DJ, Brazier, RE. Beaver dams attenuate flow: A multi-site study. Hydrological Processes. 2021; 35:e14017. https://doi.org/10.1002/hyp.14017
Scamardo, Julianne E., Marshall, Sarah, and Wohl, Ellen. 2022. Estimating Widespread Beaver Dam Loss: Habitat Decline and Surface Storage Loss at a Regional Scale. Ecosphere 13(3): e3962. https://doi.org/10.1002/ecs2.3962
Wildlife Services, Department of Agriculture Animal and Plant Health Inspection Service, 2016 Program Data Reports, March 2017, https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/sa_reports/sa_pdrs/ (June 26, 2017).
Wohl, Ellen. 2021. Legacy effects of loss of beavers in the continental United States. Environ. Res. Lett. 16 025010
Annegret Larsen, Joshua R. Larsen, Stuart N. Lane. 2021. Dam builders and their works: Beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems. Earth-Science Reviews, Volume 218, 2021, 103623, ISSN 0012-8252, https://doi.org/10.1016/j.earscirev.2021.103623.
Atwater, Alice. 1996. Water: A Natural History. Published by Basic Books. 224 pages.
Castro, Janine & Pollock, Michael & Jordan, Chris & Lewallen, Gregory & Woodruff, Kent. 2017. The Beaver Restoration Guidebook Working with Beaver to Restore Streams, Wetlands, and Floodplains. Prepared by US Fish and Wildlife Service North Pacific Landscape Conservation Cooperative.
Dittbrenner, Benjamin J., Schilling, Jason W., Torgersen, Christian E., and Lawler, Joshua J. 2022. Relocated Beaver Can Increase Water Storage and Decrease Stream Temperature in Headwater Streams. Ecosphere 13(7): e4168. https://doi.org/10.1002/ecs2.4168
Jacobs, Jefferson. 2021. BeaverHOODS: A customizable conceptual model for guiding beaver ecology, education, reach-scale restoration implementation, and watershed-scale restoration strategies. Conference presentation: River Restoration Northwest Speaker Series. doi: 10.13140/RG.2.2.30563.27686.
Muhawenimana, V., Follett, E., Maddock, I., Wilson, C. 2023. Field-based monitoring of instream leaky barrier backwater and storage during storm events. Journal of Hydrology, Volume 622, Part A. 129744, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2023.129744.
Puttock, A, Graham, HA, Ashe, J, Luscombe, DJ, Brazier, RE. Beaver dams attenuate flow: A multi-site study. Hydrological Processes. 2021; 35:e14017. https://doi.org/10.1002/hyp.14017
Scamardo, Julianne E., Marshall, Sarah, and Wohl, Ellen. 2022. Estimating Widespread Beaver Dam Loss: Habitat Decline and Surface Storage Loss at a Regional Scale. Ecosphere 13(3): e3962. https://doi.org/10.1002/ecs2.3962
Wildlife Services, Department of Agriculture Animal and Plant Health Inspection Service, 2016 Program Data Reports, March 2017, https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/sa_reports/sa_pdrs/ (June 26, 2017).
Wohl, Ellen. 2021. Legacy effects of loss of beavers in the continental United States. Environ. Res. Lett. 16 025010
