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. Last year 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. Last year 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 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 next, 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 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 next, 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.
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
