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There is substantial evidence that beaver-related restoration, via beaver translocation and the construction of beaver dam analogues, has the potential to increase the climate resiliency of Washington’s stream and riparian ecosystems (summarized in Table 1). By reducing summer water temperatures, increasing summer flows, and enhancing floodplain habitat, beavers and beaver-related restoration can benefit species of conservation concern, including trout, salmon, and amphibians. In addition, beaver-related restoration can ameliorate the negative impacts of high-flow events, create fire-resistant habitat patches in fire-prone landscapes, and foster heterogeneous mosaics of habitat that enhance the watershed-level biodiversity of aquatic and riparian ecosystems. However, these benefits are only likely to accrue under certain conditions, and there is a gap between our understanding of the aspirational potential of beaver-related restoration (what it can accomplish) and the realized benefits of restoration actions (what it does accomplish).
Engineered leaky barriers are increasingly used as natural flood management methods providing ecosystem and water quality benefits in addition to flood attenuation, complementing hard engineering flood defences. Fieldbased monitoring of a natural flood management site, Wilde Brook in the Corvedale catchment, England (UK) studied the rainfall-runoff relationship for a 5.36 km reach with 105 leaky barriers over two years. Paired pressure transducers were placed upstream and downstream of three channel spanning leaky barriers, allowing evaluation of upstream backwater rise relative to rainfall intensity, storm magnitude, and frequency. By increasing backwater rise, the leaky barriers caused overbank flows, resulting in a reduction in the crosssectional area velocity after the event. The incidence of overbank flow depended on the local stream crosssectional profile, barrier properties, location in the reach, and storm magnitude.
Beavers are ecosystem engineers that create and maintain riparian wetland ecosystems in a variety of ecologic, climatic, and physical settings. Despite the large-scale implications of ongoing beaver conservation and range expansion, relatively few landscape-scale studies have been conducted, due in part to the significant time required to manually locate beaver dams at scale. To address this need, we developed EEAGER—an image recognition machine learning model that detects beaver complexes in aerial and satellite imagery. We developed the model in the western United States using 13,344 known beaver dam locations and 56,728 nearby locations without beaver dams. Performance assessment was performed in twelve held out evaluation polygons of known beaver occupancy but previously unmapped dam locations. These polygons represented regions similar to the training data as well as more novel landscape settings. Our model performed well overall (accuracy = 98.5%, recall = 63.03%, precision = 25.83%) in these areas, with stronger performance in regions similar to where the model had been trained. We favored recall over precision, which results in a more complete catalog of beaver dams found but also a higher incidence of false positives to be manually removed during quality control. These results have far-reaching implications for monitoring of beaver-based river restoration, as well as potential applications detecting other complex landforms.
Restoring Western Headwater Streams with Low-Tech Process-Based Methods: A Review of the Science and Case Study Results, Challenges and Opportunities
This report reviews published research and unpublished case study information on the effects ofrestoring incised and degraded headwater streams in western states with low-tech processbased restoration methods (LTPBR). LTPBR is a subset of process-based restoration (PBR) that seeks to re-establish natural stream processes by reconnecting incised streams with their floodplains and adjacent wetlands so that more frequent inundation of the floodplain occurs. Projects involve the use of simple, temporary, hand-built wood and rock structures that mimic
natural beaver structures, acting as speed bumps that capture sediments to aggrade the stream. LTPBR approaches are substantially less expensive than form-based stream restoration approaches that employ heavy equipment.i This approach is appealing in part because low project costs enable implementation at a scale that can respond to the extent of floodplain alteration, which is estimated at 45% of headwaters streams in Colorado. ii Negative effects of disconnected floodplains include lower groundwater tables, lower summer base flows,
warmer water temperatures, and substantial loss of riparian habitat.
Within the State of Maryland, the potential water quality benefits of beaver are not recognized as contributing to regulatory-mandated pollution reductions. Therefore, jurisdictions lack a regulatory incentive to either encourage beaver colonization or manage and protect existing beaver habitat. Such an incentive is important, as conflicts between human and beaver habitat regularly arise. While beaver habitat often increases the groundwater table and the wetted extent of a stream system, this is not always welcomed by homeowners and can result in beaver being trapped out, with beaver dams dismantled. If beaver ponds were a recognized BMP to improve water quality, it would assist local jurisdictions with the development of beaver habitat conservation programs via easements and adaptive management. Rather than living on top of nature and replicating nature’s original ecosystem engineers with significant amounts of tax dollars, citizens could live with nature allowing tax dollars to go further, and implement more ecological restoration.
The fluxes and concentrations of materials from two contiguous second-order watersheds in the Coastal Plain of Maryland, U.S.A. were measured for six years prior to and six years subsequent to the formation of a 1.25 ha beaver pond near the bottom of one of the watersheds. The watersheds have a clay aquiclude and were equipped with V-notch weirs and continuous volume-integrating water samplers. The beaver pond reduced annual discharge of water, total-N, total-P, dissolved silicate, TOC, and TSS by 8, 18, 21, 32, 28, and 27%, respectively. Most of the total-N reduction was due to increased retention of nitrate in the winter and spring and TON in the winter and summer. Most of the total-P reduction was the result of retention of both TPi and TOP in the winter and summer. Dissolved silicate retention peaked in the spring, while TOC and TSS retention peaked in the winter. Prior to the formation of the beaver pond, concentrations of TON, TPi, TOP, TOC, and TSS had highly significant correlations with stream discharge, especially in the winter, but subsequent to the pond there was little or no relationship between these concentrations and stream discharge. However, concentrations of nitrate in the spring and ammonium in the summer were highly correlated with stream discharge both before and after the formation of the beaver pond and regressions of discharge versus concentrations of these nutrients explained more of the variation in concentrations after the formation of the pond.
Beavers are ecosystem engineers that can dramatically change the shape of the landscape and how water moves through it. They create and maintain wetland environments across North America and Eurasia in a wide variety of places, including mountains, deserts, coasts, forests, grasslands, shrublands, etc. Despite their large influence on the landscape, there are very few programs that monitor them at the landscape, regional, or continental scale. This is partially due to how much time it takes to find and identify beaver dams in satellite and aerial images. To make it easier for us to find and understand the influence of beavers at larger scales, we built a model that can automatically find beaver dams in satellite and aerial imagery. While our model is trained to find beaver dams, this type of model has promise for finding other landscape features too. The model isn’t perfect, but it is a strong starting point and will continue to improve as more people use it.
Relics of beavers past: time and population density drive scale-dependent patterns of ecosystem engineering
Like many ecological processes, natural disturbances exhibit scale-dependent dynamics that are largely a function of the magnitude, frequency and scale at which they are assessed. Ecosystem engineers create patch-scale disturbances that affect ecological processes, yet we know little about how these effects scale across space or vary through time. Here, we investigate how patch disturbances by beavers Castor canadensis, ecosystem engineers renowned for their pond-creation behavior, affect ecological processes across space and time. We evaluated how beaver population recovery influenced surface water dynamics in relation to population density over 70 years across multiple spatial scales (pond, watershed and regional) in northern Minnesota. Surface water area was positively related to population density at the watershed scale; however, despite variation in beaver densities (and therefore surface water area) at the watershed scale, regional-scale surface water area was stable through time. This stability appears to have been driven by asynchronous beaver density fluctuations among watersheds, combined with the increasing importance of abandoned ponds. Beavers initially created and occupied larger ponds with greater surface water area, but through time shifted towards occupying smaller ponds. As ponds accumulated on the landscape proportionally more surface water was stored within abandoned ponds, which offset the smaller size of occupied ponds. Beaver engineering – driven by density-dependent mechanisms and the legacy effects from abandoned ponds – not only follows general patterns of patch disturbance dynamics by creating a spatial mosaic of patches, but the organism-created mosaic also appears to generate ecological stability at greater spatial scales. We suggest restoring beavers to landscapes is a viable method for increasing surface water storage and will ultimately help advance numerous conservation and rewilding objectives. Our study demonstrates that ecosystem engineering effects can be scale-dependent, indicating researchers should evaluate the ecological impact of engineers across diverse spatiotemporal scales to fully understand their functional roles in ecosystems.
Rivers and streams, when fully connected to their floodplains, are naturally resilient systems that are increasingly part of the conversation on nature-based climate solutions. Reconnecting waterways to their floodplains improves water quality and quantity, supports biodiversity and sensitive species conservation, increases flood, drought and fire resiliency, and bolsters carbon sequestration. But, while the importance of river restoration is clear, beaver-based restoration—for example, strategic coexistence, relocation, and mimicry—remains an underutilized strategy despite ample data demonstrating its efficacy. Climate-driven disturbances are actively pushing streams into increasingly degraded states, and the window of opportunity for restoration will not stay open forever. Therefore, now is the perfect time to apply the science of beaver-based low-tech process-based stream restoration to support building climate resilience across the landscape. Not every stream will be a good candidate for beaver-based restoration, but we have the tools to know which ones are. Let us use them.
A Review of Two Novel Water-Tight Beaver Dam Analogs (WTBDA) to Restore Eroded Seasonal Creeks in Drain Tile Zones to Permanent Beaver Wetlands
Reducing nutrient runoff in streams is an important task to reduce algae blooms and associated environmental damage in large waterbodies. Beaver Dam Analogs (WTBDA) are an means to address this problem. These Water Tight Beaver Dam Analogs (WTBDA) present a novel approach to this technique that also aim to restore eroded seasonal creeks to perennial wetlands.
To What Extent Might Beaver Dam Building Buffer Water Storage Losses Associated with a Declining Snowpack?
This thesis provides a Beaver Dam Surface Water Estimation Algorithm, a model that takes observation data of 500 beaver dams to quantify the distribution of dam sizes, then using that data to develop a model for predicting water storage. While the water storage provided by beaver dams is only a small fraction of expected snow water equivalent loss, it is not insubstantial and may prove beneficial for ecosystems where human-made reservoirs are not available to regulate hydrologic regimes.
We used a spatial survey of fish assemblage structure in streams and beaver ponds to: (1) determine the effects of beavers on fish assemblage structure at the reach and drainage basin scales, and (2) assess the influences of pond age, watershed position, and pond environment on fish assemblage structure within beaver ponds.
In this study, we modeled 12 beaver dam cascade scenarios in two catchments for eight flood events with a two-dimensional (2D) hydrodynamic model.
Effect of beaver dams on the hydrology of small mountain streams: Example from the Chevral in the Ourthe Orientale basin, Ardennes, Belgium
This research focuses on the hydrological effects of a series of six beaver dams on the Chevral River, a second order tributary of the Ourthe Orientale River in a forested area of the Ardennes.
Beaver (Castor Canadensis) of the Salinas River: A Human Dimensions-Inclusive Overview for Assessing Landscape-Scale Beaver-Assisted Restoration Opportunities
Study to gather and produce human dimensions-inclusive, basin-centralized beaver knowledge through an explorative, benefits-maximizing approach to landscape-scale BAR opportunities assessment in the Salinas River.
In this study, we tracked beaver dam distributions and monitored water temperature throughout 34 km of stream for an eight-year period between 2007 and 2014. Our results suggest that creation of natural and/or artificial beaver dams could be used to mitigate the impact of human induced thermal degradation that may threaten sensitive species.
Study of flood dynamics created by American beaver (C. canadensis K.) in a southern boreal landscape in Finland in
Beaver dams, hydrological thresholds, and controlled floods as a management tool in a desert riverine ecosystem, Bill Williams River, Arizona
Testing the hypothesis that controlled floods intended to drive the fluvial geomorphic and hydrologic processes necessary
for native tree recruitment will simultaneously destroy beaver dams.
Idaho rancher, Jay Wilde, and Joe Wheaton from Utah State University use BRAT, beaver restoration assessment tool, and identified good beaver habitat to help restore Birch Creek to year-round stream flow.
Idaho rancher, Jay Wilde, partnered with Anabranch Solutions to build BDAs, and the USFS and Idaho Fish & Game to relocate beavers into Birch Creek to help restore year-round stream flow.