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The use of beavers in riparian/aquatic habitat restoration of cold desert, gully-cut stream systems in southwestern Wyoming

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... Emergent aquatic insects fuel both the aquatic and terrestrial food webs (Nakano and Murakami, 2001). The idea that beaver may promote a strong base for both food webs was supported in southwestern Wyoming where the introduction of beaver was associated with a 20% increase in avian species richness (Apple et al., 1984). Beaver damming has also been shown to increase riparian vegetation, raise water levels, attenuate flood peaks and alter sediment transport and storage patterns (McCullough et al., 2005). ...
... Using beaver as river engineers is a more natural solution than the intensive and disruptive creation of an inset floodplain using heavy equipment (Pollock et al., 2007). The use of beaver for river and riparian rehabilitation has been implemented at some sites and met with successful recolonization of beaver, local increase in water table elevation and reinvigoration of riparian vegetation (Apple et al., 1984;Albert et al., 2000;Demmer and Beschta, 2008). The success of these projects has been attributed to aggradation of sediment upstream of dams (Pollock et al., 2007). ...
... Dam failures are more common in areas where willow, or other small diameter woody vegetation, is used in dam construction as opposed to larger trees (Beedle, 1991). Therefore, at sites where building material may limit dam longevity, and thus aggradation of sediment, land managers are adding stabilization materials such as reinforcement posts or tires after beavers have built their dams, making the dams a more permanent feature (Apple et al., 1984;Bouwes et al., 2009). The idea is that dams that remain in place for longer periods will raise stream bed levels to help repair incised streams. ...
... Other studies have found that dam presence in dryland streams is strongly associated with low stream gradient (as in temperate streams; Baker and Hill, 2003), and also with alluvial substrate, gentle bank slopes, and presence of hardwood or riparian vegetation (McComb et al., 1990;Lind, 2002). When riparian trees are not available, beavers may construct dams of willow (Salix sp.; Call, 1970), cattails (Typha sp.; Andersen and Shafroth, 2010), or even sagebrush (Artemisia sp.; Apple et al., 1985), but authors suggest that such dams are likely to be less stable than those constructed with large wood. The typical hydrology and relatively limited vegetation of dryland streams suggests the hypothesis that beaver dams in dryland streams will be less abundant than in temperate streams. ...
... Furthermore, there is a positive feedback relationship between dams and channel form: stable beaver dams promote aggradation and overbank flooding, which spreads and dissipates flood energy across the floodplain; within incised channels, however, concentrated flood energy typically washes out beaver dams in their first year (Demmer and Beschta, 2008;Johnson, 2011;Pollock et al., 2012), thus preventing development of the stable beaver colonies that might counteract the incision. Artificially stabilizing beaver dams or damlike structures within incised channels has been proposed as a management technique to break the incision cycle and enhance the restoration potential of beaver dams (Apple et al., 1985;Pollock et al., 2012). ...
... The importance of these hydrological effects for vegetation is likely to be even greater within dryland streams, where lowered water tables caused by water diversion and groundwater extraction is considered a serious threat to cottonwood-willow forest (Stromberg et al., 1996). Cooke and Zack (2008) found a positive association between beaver dam density and width of riparian vegetation cover in semi-arid Wyoming, and several studies anecdotally report a general increase in abundance of willow and other vegetation over time following the return of beaver dams to semi-arid streams (Apple et al., 1985;Demmer and Beschta, 2008), although in each case these results are confounded by concurrent exclusion of livestock grazing. Reductions in non-native tamarisk due to flooding behind beaver dams have also been reported anecdotally (Albert and Trimble, 2000;Baker and Hill, 2003;Longcore et al., 2007), and in contrast to the more positive effects of beaver herbivory (see 'Effects of herbivory on non-native plants' above). ...
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After near‐extirpation in the early 20th century, beaver populations are increasing throughout many parts of North America. Simultaneously, there is an emerging interest in employing beaver activity for stream restoration in arid and semi‐arid environments (collectively, ‘drylands’), where streams and adjacent riparian ecosystems are expected to face heightened challenges from climate change and human population growth. Despite growing interest in reintroduction programmes, surprisingly little is known about the ecology of beaver in dryland streams, and science to guide management decisions is often fragmented and incomplete. This paper reviews the literature addressing the ecological effects and management of beaver activity in drylands of North America, highlighting conservation implications, distinctions between temperate and dryland streams, and knowledge gaps. Well‐documented effects of beaver activity in drylands include changes to channel morphology and groundwater processes, creation of perennial wetland habitat, and substantial impacts to riparian vegetation. However, many hypothesized effects derived from temperate streams lack empirical evidence from dryland streams. Topics urgently in need of further study include the distribution and local density of beaver dams; consequences of beaver dams for hydrology and water budgets; and effects of beaver activity on the spread of aquatic and riparian non‐native species. In summary, this review suggests that beaver activity can create substantial benefits and costs for conservation. Where active beaver introductions or removals are proposed, managers and conservation organizations are urged to implement monitoring programmes and consider the full range of possible ecological effects and trade‐offs. Copyright © 2014 John Wiley & Sons, Ltd.
... Pendant les crues, un barrage isolé ne pourra retenir qu'une faible quantité d'eau, mais une série de barrages tout au long d'un cours d'eau aura un impact beaucoup plus significatif. En amortissant le débit et la vitesse du courant, les barrages peuvent amoindrir l'érosion potentielle d'une crue (Apple et al., 1984;Parker, 1986). ...
... Plusieurs études rendent compte de la capacité du barrage de castors à réduire l'incision fluviale dans les zones soumises à l'érosion régressive du lit (Apple et al., 1984, Parker et al., 1985. En liaison avec le ralentissement du débit, les barrages induisent une diminution de la capacité de transport de sédiments et donc une augmentation des dépôts. ...
Chapter
• impact de l'activité du castor sur les biocénoses aquatiques (synthèse bibliographique) - in French
... With beaver loss being one of the suggested reasons for the incision of stream systems, a potential solution is re-introducing beaver and promoting building of beaver dams at sites where the health and extent of riparian zones are limited by stream incision. Beaver have been used in some river and riparian rehabilitation projects that led to successful re-colonization of beaver, local increase in water table elevation and reinvigoration of riparian vegetation (Apple et al., 1984;Albert and Trimble, 2000;Demmer and Beschta, 2008). The success of these projects has been attributed, in part, to accumulation of sediment and a rise in bed level upstream of dams where fine sediment accumulation has been well documented (Pollock et al., 2007). ...
... Dam failures are more common in areas where willow or other small diameter woody vegetation is used in dam construction as opposed to larger trees (Beedle, 1991). Where building material may limit beaver dam longevity, some land managers have added stabilizing materials, such as posts or tires (Apple et al., 1984;Bouwes et al., 2009). Although artificially reinforced dams that remain in place for longer periods may increase aggradation and help repair incised streams, it is possible that these local, semi-permanent dams may have unintended consequences, analogous to the 2−5 m high mill dams that have impacted many streams in the eastern United States (Walter and Merritts, 2008;Merritts et al., 2011). ...
Article
Beaver dams in streams are generally considered to increase bed elevation through in-channel sediment storage, thus, reintroductions of beaver are increasingly employed as a restoration tool to repair incised stream channels. Here we consider hydrologic and geomorphic characteristics of the study stream in relation to in-channel sediment storage promoted by beaver dams. We also document the persistence of sediment in the channel following breaching of dams. Nine reaches, containing 46 cross-sections, were investigated on Odell Creek at Red Rock Lakes National Wildlife Refuge, Centennial Valley, Montana. Odell Creek has a snowmelt-dominated hydrograph and peak flows between 2 and 10 m3 s− 1. Odell Creek flows down a fluvial fan with a decreasing gradient (0.018–0.004), but is confined between terraces along most of its length, and displays a mostly single-thread, variably sinuous channel. The study reaches represent the overall downstream decrease in gradient and sediment size, and include three stages of beaver damming: (1) active; (2) built and breached in the last decade; and (3) undammed. In-channel sediment characteristics and storage were investigated using pebble counts, fine-sediment depth measurements, sediment mapping and surveys of dam breaches. Upstream of dams, deposition of fine (≤ 2 mm) sediment is promoted by reduced water surface slope, shear stress and velocity, with volumes ranging from 48 to 182 m3. High flows, however, can readily transport suspended sediment over active dams. Variations in bed-sediment texture and channel morphology associated with active dams create substantial discontinuities in downstream trends and add to overall channel heterogeneity. Observations of abandoned dam sites and dam breaches revealed that most sediment stored above beaver dams is quickly evacuated following a breach. Nonetheless, dam remnants trap some sediment, promote meandering and facilitate floodplain development. Persistence of beaver dam sediment within the main channel on Odell Creek is limited by frequent breaching (< 1–5 years), so in-channel sediment storage because of damming has not caused measurable channel aggradation over the study period. Enhanced overbank flow by dams, however, likely increases fine-grained floodplain sedimentation and riparian habitat. Contrasts between beaver-damming impacts on Odell Creek and other stream systems of different scales suggest a high sensitivity to hydrologic, geomorphic, and environmental controls, complicating predictions of the longer-term effects of beaver restoration.
... and Naiman 1988). The ability of beaver impoundments to reduce stream velocity and therefore reduce fluvial incision in areas undergoing gully erosion, and correspondingly induce sedimentation in the reservoir is well documented (Apple et al. 1985; Parkeret aI. 1985; Naiman et al. 1988). ...
... 1985; Naiman et al. 1988). As Apple et al. (1985) point out, a series of beaver dams and ponds along a stream step down the flow velocities, reducing the carrying power of the stream (as velocity drops, stream discharge drops, in turn reducing erosion potential and leading to accelerated deposition rather than erosion). Hand in hand with sedimentation in beaver ponds is the reduction of suspended sediment in, and improvement of water quality of, streamwater emerging from beaver ponds (Figure 3; Appendix 1). ...
Article
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Animals such as the beaver can have profound geomorphic impacts on the environment in which they live. Beavers affect their environment in a variety of ways, but most profoundly through dam building. Other geomorphic influences include canal building, bank burrowing creation of runs and slides, stream piracy, and indirectly thorough karstification and outburst-floods. Teachers can use the beaver as a classroom and field trip example to illustrate the effects that animals have on the physical landscape.
... Forest Service, for instance, has used beaver to improve wetlands in Montana and Oregon, while BLM initiated beaver-transplant demonstration projects on degraded streams in southwest Wyoming (Johnson 1984, Bergstrom 1985, McKinstry and Anderson 1997, McKinstry et al. 2001 (Smith 1980, Apple 1983, McCall et al. 1996. In addition, beaver dams regulate stream flow by storing water, reducing peak or flood flow, and augmenting low flows during summer (Smith 1983b), During dry periods, 30 to 60 percent of the water in a stream system can be held in beaver ponds (Smith 1983a). ...
... Presumably, this relates to some aspect of habitat quality, given that successful beaver restorations supplemented vegetation or targeted areas with abundant vegetation (e.g. Apple et al. 1985;Albert & Trimble 2000;Pollock et al. 2015). Most studies on habitat requirements of beavers have been conducted in ecoregions with different habitat types than found in the arid west (Baker & Hill 2003). ...
Article
The North American beaver (Castor canadensis) builds dams that pond water on streams, which provide crucial ecological services to aquatic and riparian ecosystems and enhance biodiversity. Consequently, there is increasing interest in restoring beavers to locations where they historically occurred, particularly in the arid western United States. However, despite often intensive efforts to reintroduce beavers into areas where they were severely reduced in numbers or eliminated due to overharvesting in the eighteenth and nineteenth centuries, beavers remain sparse or missing from many stream reaches. Reasons for this failure have not been well studied. Our goal was to evaluate certain biotic factors that may limit the occurrence of dam-building beavers in northern New Mexico, including competitors and availability of summer and winter forage. We compared these factors at primary active dams and at control sites located in stream reaches that were physically suitable for dam-building beavers but where none occurred. Beaver dams mostly occurred at sites that were not grazed or where there was some alternative grazing management, but were mostly absent at sites within Forest Service cattle allotments. Results indicated that cattle grazing influenced the relation between vegetation variables and beaver presence. The availability of willows (Salix spp.) was the most important plant variable for the presence of beaver dams. We conclude that grazing by cattle as currently practiced on Forest Service allotments disrupts the beaver-willow mutualism, rendering stream reaches unsuitable for dam-building beavers. We recommend that beaver restoration will require changes to current livestock management practices.
... Beaver dams do not significantly influence streamflow in all environments. In the western United States where many streams are deeply incised, streamflow regulation may not occur to a great extent as beaver may not be able to build a dam high enough to extensively pond water (Apple et al., 1985). However, beaver dams may enhance water storage in floodplain soils, that is, 'bank storage', along losing stream reaches (Gurnell, 1998;Hillman, 1998). ...
Article
Hydrological and geomorphological processes are influenced by beaver (. Castor canadensis and C. fiber) activities in aquatic and semi-aquatic environments throughout much of North America, Eurasia, and the austral archipelago of Chile and Argentina. The main hydrologic signature of beaver activities varies with hydrogeomorphic setting - along confined streams it is the pond formed upstream of dams, along unconfined streams it is downstream flooding on floodplains and terraces, and in preexisting wetlands it is the formation of open-water bodies. A review of the existing literature shows that it is rich with descriptions of how beaver activities influence specific hydrologic and geomorphic processes. The main findings are that beaver dams moderate stream flows, increase surface water and riparian groundwater storage, regulate hyporheic flows, and enhance evapotranspiration rates. Beavers also excavate canals on the margins of beaver ponds and create extensive burrow systems in riverbanks where damming is not possible. Bank burrows are also common in beaver ponds. Missing in the beaver hydrogeomorphological literature, however, are clear linkages between affected hydrological processes and ecosystem functioning, especially at larger spatial and temporal scales. In addition, knowledge of effects of beaver activities on the form and function of the expansive peatlands that span northern latitudes is lacking.
... Several studies confirm that aspen, willow, and cottonwood are preferred forage and dam-building material (Kimball and Perry, 2008;Warren, 1926), other research shows a strong association between beaver presence and willow (Baker and Hill, 2003;Mortenson et al., 2008;Tallent et al., 2011) as well as dam presence and riparian trees (Mccomb et al., 1990). When preferred materials are not available, herbaceous wetland vegetation like cattail (Typha spp.; Andersen and Shafroth, 2010) and upland woody vegetation (Warren, 1927), or sagebrush (Artemisia spp.; Apple et al., 1985), can be used for dam construction. Based on these preferences, we assigned a single numeric suitability value from 0 to 4 to each of the land cover classes, with zero representing unsuitable food/building material and four representing preferred food and building material. ...
Article
Abstract The construction of beaver dams facilitates a suite of hydrologic, hydraulic, geomorphic, and ecological feedbacks that increase stream complexity and channel–floodplain connectivity that benefit aquatic and terrestrial biota. Depending on where beaver build dams within a drainage network, they impact lateral and longitudinal connectivity by introducing roughness elements that fundamentally change the timing, delivery, and storage of water, sediment, nutrients, and organic matter. While the local effects of beaver dams on streams are well understood, broader coverage network models that predict where beaver dams can be built and highlight their impacts on connectivity across diverse drainage networks are lacking. Here we present a capacity model to assess the limits of riverscapes to support dam-building activities by beaver across physiographically diverse landscapes. We estimated dam capacity with freely and nationally-available inputs to evaluate seven lines of evidence: (1) reliable water source, (2) riparian vegetation conducive to foraging and dam building, (3) vegetation within 100 m of edge of stream to support expansion of dam complexes and maintain large colonies, (4) likelihood that channel-spanning dams could be built during low flows, (5) the likelihood that a beaver dam is likely to withstand typical floods, (6) a suitable stream gradient that is neither too low to limit dam density nor too high to preclude the building or persistence of dams, and (7) a suitable river that is not too large to restrict dam building or persistence. Fuzzy inference systems were used to combine these controlling factors in a framework that explicitly also accounts for model uncertainty. The model was run for 40,561 km of streams in Utah, USA, and portions of surrounding states, predicting an overall network capacity of 356,294 dams at an average capacity of 8.8 dams/km. We validated model performance using 2852 observed dams across 1947 km of streams. The model showed excellent agreement with observed dam densities where beaver dams were present. Model performance was spatially coherent and logical, with electivity indices that effectively segregated capacity categories. That is, beaver dams were not found where the model predicted no dams could be supported, beaver avoided segments that were predicted to support rare or occasional densities, and beaver preferentially occupied and built dams in areas predicted to have pervasive dam densities. The resulting spatially explicit reach-scale (250 m long reaches) data identifies where dam-building activity is sustainable, and at what densities dams can occur across a landscape. As such, model outputs can be used to determine where channel–floodplain and wetland connectivity are likely to persist or expand by promoting increases in beaver dam densities.
... fiber) beavers historically impounded low-order streams and created ponds. The location and distribution of beaver dams acted to reduce stream velocity, elevate local water tables, and induce sedimentation (RUEDEMANN & SCHOONMAKER 1938, APPLE et al. 1985JOHNSTON & NAIMAN 1987, MARET et al. 1987, COLEMAN & DAHM 1990, WOOD & WADDINGTON 1990, BUTLER 1991, MARSTON 1994. The beaver's potential geomorphic influence on the landscape is, however, only as great as the number of beavers present. ...
Article
Full-text available
Whereas the role of beaver dams and the resulting sedimentation processes are increasingly understood, little is known about the amount of sediment transported into a beaver pond as a result of other common beaver activities, such as burrowing and trampling. Volumetric measurements of beaver-induced streambank erosion showed that beavers are important agents of landscape alteration along an 817 m stretch of Bolin Creek, North Carolina. Conspicuous zoogeomorphic landforms were identified and analyzed, including 288 bank-slides and 27 landforms that we termed 'tunnel slides'. Measurements yielded a sediment loss of approximately 22 m3 into the stream system over a 5 year period of beaver activity, resulting in an erosion rate of 0.054 m3 per 10 meters of stream per year. Bankslide activity accounted for considerably more soil loss than tunnel slides, ca. 20 m3 and 2 m3, respectively. However, 'tunnel slide' burrowing may have a greater geomorphic impact than presently quantified. These burrows often disrupted tree root systems along the streambank edges, causing increased erosion due to tree tipping. Soil loss was significantly greater along the west bank. An adjacent recreational trail along the east bank may function as a barrier limiting browse access, resulting in less beaver activity.
... Beaver can benefit willow establishment and survival processes by maintaining high water tables throughout the growing season and by placing water and sediment where floods cannot reach (Westbrook et al. 2006, Westbrook et al. 2011. Beaver abandonment can cause dam failure, channel incision, and a lower water table, which can kill existing willow and prevent re-establishment (Apple et al. 1985, Fouty 2003. In Yellowstone National Park, USA, willow that was protected from ungulate browsing and given adequate water via simulated beaver dams were taller and more vigorous than protected willow in undammed sites (Bilyeu et al. 2008). ...
Article
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Beaver (Castor spp.) conservation requires an understanding of their complex interactions with competing herbivores. Simulation modeling offers a controlled environment to examine long-term dynamics in ecosystems driven by uncontrollable variables. We used a new version of the SAVANNA ecosystem model to investigate beaver (C. canadensis) and elk (Cervus elaphus) competition for willow (Salix spp.). We initialized the model with field data from Rocky Mountain National Park, Colorado, USA, to simulate a 4-ha riparian ecosystem containing beaver, elk, and willow. We found beaver persisted indefinitely when elk density was <= 20 elk km (2). Beaver persistence decreased exponentially as elk density increased from 30 to 60 elk km(2), which suggests the presence of an ecological threshold. The interaction of beaver and elk herbivory shifted the size distribution of willow plants from tall to short when elk densities were >= 30 elk km (2). The loss of tall willow preceded rapid beaver declines, thus willow condition may predict beaver population trajectory in natural environments. Beaver were able to persist with slightly higher elk densities if beaver alternated their use of foraging sites in a rest-rotation pattern rather than maintained continuous use. Thus, we found asymmetrical competition for willow strongly favored elk over beaver in a simulated montane ecosystem. Finally, we discuss application of the SAVANNA model and mechanisms of competition relative to beaver persistence as metapopulations, ecological resistance and alternative state models, and ecosystem regulation.
... which normally occurs when willows are dormant, promotes suckering and rapid growth (Kindschy 19X9). These characteristics have prompted land managers to use both beaver and willow as tools for riparian restoration (Apple et al. 1985, Conroy and Svejcar 1991). However, in high elevation shrub-steppe ecosystems , willows may be the only winter food and limit beaver populations (pers. ...
Article
Beaver (Castor can&e&s Kuhl) and willow (Sulk spp.) are important components of riparian restoration on degraded west-ern rangelands. Land managers need quantitative information to evaluate carrying capacity and potential habitat quality for beavers in riparian-willow systems. Our objectives were to deter-mine the best model to predict biomass components of coyote mil-low (S. exiguu Nuttall) from basal stem diameters and compare model predictions to diameter class averages. The study was con-ducted in a shrub-steppe ecosystem of northwestern Colorado. We estimated oven-dried weights of annual and total beaver food and total live biomass by diameter class from a sample of 160 willow stems. Several variants of a logistic function were fit with nonlinear least squares regression to select a model that best pre-dicted mean biomass by stem diameter. A four-parameter logis-tic model provided the best fit for all 3 stem components. Predicted biomass estimates of beaver food and total live biomass had smaller standard errors than sample means for all 10 stem diameter class midpoints. Percentage of stem weight that was beaver food varied from 93.6% for the smallest stems to 12.2% for the largest. We concluded that the logistic model provided reliable estimates of beaver food biomass and could be used with food consumption rates and stem density data to evaluate carry-ing capacity for beaver or test assumptions in the beaver habitat suitability indes model.
... fiber) beavers historically impounded low-order streams and created ponds. The location and distribution of beaver dams acted to reduce stream velocity, elevate local water tables, and induce sedimentation (RUEDEMANN & SCHOONMAKER 1938, APPLE et al. 1985JOHNSTON & NAIMAN 1987, MARET et al. 1987, COLEMAN & DAHM 1990, WOOD & WADDINGTON 1990, BUTLER 1991, MARSTON 1994. The beaver's potential geomorphic influence on the landscape is, however, only as great as the number of beavers present. ...
... Livestock grazing must be managed prior to reintroductions to ensure adequate aquatic and riparian plant biomass for beaver summer food, and to permit sufficient growth of willows or other woody vegetation for winter food . At ecologically damaged sites, aspen, willow, or cottonwood can be provisioned at the site to ensure adequate winter food and building materials until riparian vegetation develops from dam-building activity ( Apple et al. 1985). In streams that are prone to flooding, initial dams built by reintroduced beavers may wash out. ...
Article
ACKNOWLEDGMENTS Wethank Dave McDonald, University of Wyoming, Department of Zoology, who performed the population matrix analysis and identified the important conservation conclusions of the analysis. Many biologists and researchers contributed data, unpublished reports, and their personal expertise to this assessment. The following deserve special mention: Jerry Apker, Colorado Division of Wildlife; Mace Hack and Jeff Hoffman, Nebraska Game and Parks Commission; Alyssa Kiesow, South Dakota Department of Game, Fish, and Parks; Matt Peek, Kansas Department ofWildlife and Parks; and Reg Rothwell, Wyoming Game and Fish Department. Gary Patton and Greg Hayward, USDA Forest Service, Rocky Mountain Region, provided key guidance and tirelessly answered many questions. Lynn Wickersham, Ecosphere Environmental Services, provided administrative and technical support. Finally, we are grateful to Andrea Easter-Pilcher, University of Montana-Western, and Bruce Schulte, Georgia Southern University, for their helpful reviews of an earlier draft of this manuscript. AUTHORS’ BIOGRAPHIES Steve Boyle is Senior Biologist and owner of BIO-Logic Environmental in Montrose, Colorado. He holds anMS degree in Wildlife Biology (Colorado State University, 1981) and has 28 years of experience in biological assessments, natural resource planning, and wildlife management and research in the western United States and overseas. He authored the USDA Forest Service Region 2 River Otter Species Conservation Assessment, and has led a number,of regional conservation planning efforts including a Sagebrush Steppe Ecosystem Conservation Assessment and Management Plan for the Colorado Division of Wildlife, and Statewide Programmatic Biological Evaluations for four grouse species in Colorado for the USDI Bureau of Land Management. As former Senior Wildlife Biologist for AGEISS Environmental, Inc., Mr. Boyle was Principal Investigator for research projects on
... But this hypothesis is consistent with available information: indirect support for it comes from the work of land managers who are using beaver dams—or small artificial dams—as a tool to aggrade incised streams. In Wyoming, Apple et al. (1983) provided cut cottonwood branches to recently relocated beaver who subsequently built dams that aggraded incised channels. The initial dams quickly backfilled with sediment, and the beaver continued to build additional structures upstream. ...
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Beaver dams alter the hydrology and geomorphology of stream systems and affect habitat for fishes. Beaver dams measurably affect the rates of groundwater recharge and stream discharge, retain enough sediment to cause measurable changes in valley floor mor-phology, and generally enhance stream habitat quality for many fishes. Historically, beaver dams were frequent in small streams throughout most of the Northern Hemisphere. The cumulative loss of millions of beaver dams has dramatically affected the hydrology and sediment dynamics of stream systems. Assessing the cumulative hydrologic and geomorphic effects of depleting these millions of wood structures from small and medium-sized streams is urgently needed. This is particularly important in semiarid climates, where the widespread removal of beaver dams may have exacerbated effects of other land use changes, such as livestock grazing, to accelerate incision and the subsequent lowering of groundwater levels and ephemeralization of streams.
... A less expensive restoration approach would be to provide beaver with the woody material needed for food and dam construction. This approach has been tried elsewhere briefly to restore incised streams, with positive results (Apple et al., 1983;Apple, 1985). Dams were constructed and they quickly backfilled with sediment. ...
Article
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Channel incision is a widespread phenomenon throughout the dry interior Columbia River basin and other semi-arid regions of the world, which degrades stream habitat by funda-mentally altering natural ecological, geomorphological and hydrological processes. We examined the extent of localized aggradation behind beaver dams on an incised stream in the interior Columbia River basin to assess the potential for using beaver, Castor canadensis, dams to restore such channels, and the effect of the aggradation on riparian habitat. We estimated aggradation rates behind 13 beaver dams between 1 and 6 years old on Bridge Creek, a tributary to the John Day River in eastern Oregon. Vertical aggradation rates are initially rapid, as high as 0·47 m yr − − − − −1 , as the entrenched channel fills, then level off to 0·075 m yr − − − − −1 by year six, as the sediment begins accumulating on adjacent terraces. We found that a 0·5 m elevation contour above the stream channel approximately coincided with the extent of new riparian vegetation establishment. Therefore, we compared the area surrounding reaches upstream of beaver dams that were within 0·5 m elevation of the stream channel with adjacent reaches where no dams existed. We found that there was five times more area within 0·5 m elevation of the channel upstream of beaver dams, presumably because sediment accumulation had aggraded the channel. Our results suggest that restora-tion strategies that encourage the recolonization of streams by beaver can rapidly expand riparian habitat along incised streams.
... Nach JOHNSON , in DJOSHKIN & SAFONOW 1972 (APPLE et al. 1985;Mc DOWELL 1975in OLSON & HUBERT 1994. GARD (1961) berichtet von gr6geren K6rperl~ingen bei Forellen, wenngleich die Zahl der Tiere unverondert bleibt. ...
Article
Due to the return of the beaver an increasing number of brooks become restored to a natural condition. It is characterized by an alternation of flowing and standing sectors. In the summer of 1995, different groups of organisms (Odonata, Mollusca, Trichoptera, Ephemeroptera, Diptera) of two brooks in the Spessart mountains (Hesse, Germany) were studied to compare the composition of invertebrates in beaver homeranges and in the non-influenced sectors above. The new living conditions resulted in the disappearance of some species (Drusus anulatus, Trich., Sericostoma personatum, Trich., Radix peregra, Gastr.). Nevertheless the beaver homeranges accommodate a significant higher number of species of dragon flies and damsel flies, molluscs and caddis flies than the brooks above the homeranges. The heterogeneity of natural river systems make a coexistence of running water and silent water organisms possible. The examinations result in a significant higher group dominance of ephemeras (i.p. Cloeon dipterum) in a beaver pond than in lenitic sectors conditioned by the gradient without beaver influence. Here the dominance of chironomids was much higher. High current sectors with their characteristic organisms are also present in the beaver homeranges. The higher number of insects is the basis of nourishment for predatory insects and fishes. The potential effects of beaver ponds on fishes are discussed.
... streamflow regulation may not occur to a great extent as beaver may not be able to build a dam high enough to pond water (Apple et al., 1985). Storage of water in beaver ponds and on floodplains can increase the annual residence time of stream water , enhance evaporation rates (Woo and Waddington, 1990;, and increase the probability of overbank flooding with a given stream discharge (Westbrook et al., submitted). ...
Article
Thesis (Ph.D.)--Colorado State University, 2005. Includes bibliographical references.
Article
Freshwater ecosystems are some of the most biodiverse habitats, but they are among the most endangered due to human activities. In this context, beavers represent a nature‐based solutions to preserve and repair freshwater ecosystem, given their important role as ecosystem engineers. However, in an environment modified by humans, beaver activities frequently create conflicts masking the positive effects of this rodent. Therefore, the management of beaver populations and human–beaver conflicts is needed. This article investigates the literature about beaver management through a bibliometric analysis to understand past, current, and future response. Moreover, it quantifies the number of studies that consider beavers as a resource, and it identifies the emerging themes in the field. The bibliometric analysis was performed considering a total of 415 documents with the software VOSviewer and the R web interface for bibliometrix Biblioshiny. The analysis presented here provides a complete view of past, present, and future management approaches and responses at the base of beaver management strategies. Three main results emerged. Firstly, a rising tendency in the number of publications about beavers that are directly linked to the populations development and spread has detected. Secondly, only 4.3% of scientific literature has referred to beaver‐related restoration. Thirdly, the ‘human perceptions’ has resulted in the emerging field investigated. Findings suggest that there is a lot of research interest about beaver management. The beaver is still poorly managed as a tool for freshwater ecosystem restoration. The management is shifting from studies focused more so on beaver ecology to others mainly focused on the beaver effects and the human dimension. This review provides a starting point for future research on beavers and suggests the development of socio‐ecological management models that consider benefits and impacts of beavers. This will help the decision‐making process of conservation and restoration initiatives.
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Hydrological and geomorphological processes are influenced by beaver (Castor canadensis and C. fiber) activities in aquatic and semi-aquatic environments throughout much of North America, Eurasia, and the austral archipelago of Chile and Argentina. The main hydrologic signature of beaver activities varies with hydrogeomorphic setting—along confined streams it is the pond formed upstream of dams, along unconfined streams it is downstream flooding on floodplains and terraces, and in preexisting wetlands it is the formation of open-water bodies. A review of the existing literature shows that it is rich with descriptions of how beaver activities influence specific hydrologic and geomorphic processes. The main findings are that beaver dams moderate stream flows, increase surface water and riparian groundwater storage, regulate hyporheic flows, and enhance evapotranspiration rates. Beavers also excavate canals on the margins of beaver ponds and create extensive burrow systems in riverbanks where damming is not possible. Bank burrows are also common in beaver ponds. Missing in the beaver hydrogeomorphological literature, however, are clear linkages between affected hydrological processes and ecosystem functioning, especially at larger spatial and temporal scales. In addition, knowledge of effects of beaver activities on the form and function of the expansive peatlands that span northern latitudes is lacking.
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Introductions of alien animal species and re-introductions of formerly native species to their original habitats are considered. Selected examples from different regions, including Subantarctic islands, Australia, New Zealand, North America, and Europe.
Article
In California, beaver (Castor canadensis) were first recognized for their value as a furbearer. Additionally, in many areas, beaver are considered desirable if not essential components of stream and wetland ecosystems. Where beaver and human activity overlap, beaver have become nuisance animals causing direct damage through dam building, flooding, bank denning, and loss of agricultural crops. Other problems such as the threat of levee failure and subsequent flooding, increases in undesirable brush growth due to a raised water table, restricted access due to flooding, and an increased mosquito population resulted in the Department of Water Resources (DWR) developing a beaver management program. In 1984, DWR entered into a long-term agreement with the U. S. Department of Agriculture (USDA) Animal Damage Control (ADC) program to eliminate a large existing population of beaver and remove subsequent reinvading individuals from a 20-mile stretch of man-made Cherokee Canal in Butte County, California. In addition, existing dams, lodges, dens, and heavy brush growth were removed in an attempt to insure the flood safety of the project and modify the existing habitat making it less suitable for reinvading beavers. Both the costs and results of this program are discussed, as well as the long-term management strategy for this project.
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Sediment depth and stream-flow data from 10 beaver ponds illustrate that beavers (Castor canadensis) considerably influence hydrogeomorphic processes in low-order stream systems of Glacier National Park (GNP), Montana. Beaver ponds clearly trap sediment, and the depth and volume of sediment substantially increase with dam age. Beaver impoundments also reduce the velocity and discharge of streams emerging downstream of dams. Older beaver dams more efficiently reduce stream velocity and discharge than young dams. Three older dams actually precluded downstream discharge, redistributing water as hyporheic outflow. The ability of beavers to alter the hydrogeomorphic environment in the near vicinity of their ponds is dramatic, but future work is still needed to elucidate the relative importance of lowered stream energy versus the erosive potential of underloaded water downstream. [Key words: Castor canadensis, beaver dams, beaver ponds, sedimentation, biogeomorphology, hydrogeomorphology.]
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Beaver are geomorphic agents through their building of dams and cre-ation of pond environments. In the southeast United States, the successful reintroduction of beaver has vastly in-creased the number of ponds im-pounded by beaver dams. These dams may fail, producing rapid and potentially catastrophic draining of beaver ponds, a geomorphic hazard which has not gained sufficient notice. This paper examines several cases of known dam failure and subsequent rapid drainage of beaver ponds. Reconstruc-tions of the discharge from these ponds was accomplished using standard hy-drologic relationships of stream dimen-sions or pond volume to discharge. Peak flood discharges may be catastrophi-cally high . The maximum hazard for beaver-dam failure and pond outburst-flooding occurs on the Piedmont, where periodic intense rainstorms combine with rapid surface runoff and limited surface infiltration to produce high-discharge floods.
Article
Beaver (Castor canadensis) populations have declined or failed to recover in heavily browsed envi­ ronments. I suggest that intense browsing by livestock or ungulates can disrupt beaver-willow (Salix spp.) mutu­ alisms that likely evolved under relatively low herbivory in a more predator-rich environment, and that this inter­ action may explain beaver and willow declines. Field experiments in Rocky Mountain National Park, Colorado, USA, found the interaction of beaver and elk (Cervus elaphus) herbivory suppressed compensatory growth in wil­ low. Intense elk browsing of simulated beaver-cut willow produced plants which were small and hedged with a high percentage of dead stems, whereas protected plants were large and highly branched with a low percentage of dead stems. Evaluation of a winter food cache showed beaver had selected woody stems with a lower percentage of leaders browsed by elk. A lack of willow stems suitable as winter beaver food may cause beaver populations to decline, creating a negative feedback mechanism for beaver and willow. In contrast, if browsing by livestock or ungulates can be controlled, and beaver can disperse from a nearby source population, then beaver may build dams in marginal habitat which will benefit willow and cause a positive riparian response that restores proper function to degraded habitat. In a shrub-steppe riparian ecosystem of northwestern Colorado, USA, rest from overgrazing of livestock released herbaceous vegetation initiating restoration of a beaver-willow community. Thus, competition from livestock or ungulates can cause beaver and willow to decline and can prevent their res­ toration in heavily browsed riparian environments, but beaver and willow populations can recover under proper grazing management.
Article
After a long absence, beaver Castor fiber are rapidly returning to Europe. Their dam-building and tree-felling behaviour may have consequences for salmon Salmo salar and sea trout Salmo trutta management. In 2003 we investigated the parallel use of stream sections by beaver, sea trout and salmon and determined the potential hindrance that beaver dam-building presented for reproducing salmon and sea trout along 65 km of the Numedalslågen River and tributaries, a major Norwegian catchment. We also surveyed landowner attitude to having beaver on salmon and sea trout streams. Most salmon spawned in the river and most sea trout in 51 tributaries. Nine of these tributaries also hosted spawning salmon. 15 (29%) of the 51 tributaries with spawning sea trout and six (67%) of the nine with spawning salmon had intermittently been occupied by beaver. Though beaver preferred to colonize the same sections of stream used for spawning, only 15% of the stream length navigable by salmon and sea trout on the 51 tributaries had actually been used by beaver, and only three colonies were occupied autumn 2003 (1 colony/25.0 km). Five dams were functioning during autumn 2003 on the 51 tributaries (1 dam/14.3 km). These potentially hindered sea trout and salmon from reaching 18% and 3%, respectively of their potential spawning habitat, though all dams were low (≤0.5 m). Though the autumn density of occupied beaver colonies along the river (1 colony/2.5 km) was 10.0 times the density on the 51 tributaries, no dams were built on the river. Thus most salmon reproduction in the catchment was unhindered by beaver. Nine of 14 landowners were unequivocally positive about having beaver together with salmon and sea trout. We conclude that the presence of beaver on similar catchments will likely have only an insignificant negative impact on the reproduction of sea trout and salmon. Copyright © 2007 John Wiley & Sons, Ltd.
Article
page 439 Abstract The Eurasian and North American beavers are similar in their ecological requirements, and require water deep enough to cover the entrance to their lodge or burrow. A food cache is often built next to the lodge or burrow, except in some southern areas. On small streams (up to fourth order) dams are frequently built to create an impoundment, generally on low gradient streams, although at high population densities dams may be built on steeper gradient streams. On large rivers or in lakes, simply a lodge with its food cache may be built. The beaver is a keystone riparian species in that the landscape can be considerably altered by its activities and a new ecosystem created. The stream above a dam changes from lotic to lentic conditions. There are hydrological, temperature and chemical changes, depending on types of dams and locations. Although the invertebrates may be fewer per unit area, total number of organisms increases, and diversity increases as the pond ages. In cool, small order streams, the impoundments provide better habitat for large trout, possibly creating angling opportunities. However, at sites
Article
Sediment depth was measured at several sites within each of eight beaver ponds in Glacier National Park, Montana, and sediment samples wen; collected from five of these ponds. Accumulation rates of sediments far exceeded published rates from boreal forest landscapes in eastem and central North America. Pond area strongly predicts volume of sedimentation. Textural differences illustrated spatial variations associated with position in a pond and along a pond sequence. Organic matter content was significantly higher in older ponds, and has ramifications for the development of the benthos and the long-term storage of matter in ponds. The role of beavers as biogeomorphic agents is profound, but requires further elucidation to distinguish between fluvial sediment deposition in ponds and sediment deposition associated with beaver excavational activity.
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