Determining Methods to Evaluate Relations Between
Livestock and Wildlife Grazing and Water Quality
|Wayne A. Hubert
|Stanley H. Anderson
|Duffy J. Brown
|Lillian G. Herger
Wyoming Department of Environmental Quality
Wayne A. Hubert
Stanley H. Anderson
Duffy J. Brown
Lillian G. Herger
U.S. Fish and Wildlife Service
Wyoming Cooperative Fish and Wildlife
University of Wyoming
The goal of this project was to assimilate information that may be used to design research that will evaluate relations between wildlife and livestock grazing on water quality in Wyoming. This report summarizes the published and unpublished literature on relationships between livestock grazing, wild ungulate grazing, and water quality in streams in order to provide technical assistance to the Wyoming Department of Environmental Quality and the U.S. Environmental Protection Agency. The emphasis in on the impacts of large hooved mammals on riparian systems and their contribution to non-point source pollution.
Specific objectives include:
Published and unpublished data regarding the impact of both livestock and wildlife grazing on water quality and riparian habitat were summarized. There are numerous reports that summarize impacts of livestock grazing on water quality, but few reports address the impacts of wild ungulates on water quality. The major non-point source pollutants that result from ungulate grazing are sediment, bacteria, and nutrients. Sedimentation is generally the most detrimental non-point source pollutant, whereas increased bacteria levels and nutrient loads from grazing may not have the far reaching impact on the stream ecosystem as sedimentation does. Ungulates grazing on riparian zones remove and trample vegetation which causes three types of change to water quality: (1) increased summer water temperatures, (2) reduced allochthonous inputs, (3) changes to the physical feature of the stream channel.
Results vary on water quality impacts related to livestock densities. Low densities generally yield little impact to riparian zones and water quality. Light to moderate densities yield variable results in the degree of water quality or riparian zone impacts. Several studies found that moderate to heavy densities resulted in measurable non-point source pollution. The majority of literature available on the impacts of wild ungulates to water quality and riparian zones pertained to elk (Cervus elaphus) . Physical and behavioral characteristics of elk heighten the likelihood that they may cause impacts to water quality and riparian areas in Wyoming.
Published and unpublished data were summarized to evaluate the potential for the development of predictive models of the relationship of herd levels to non-point source pollution. The information available on both livestock stocking levels and wildlife herd levels was insufficient for designing predictive models of the relationship of animal densities to non-point source pollution.
The information on the affects of wild ungulates on water quality was too limited to determine how foraging behavior, seasonal movement, or winter feeding concentrations may influence water quality. It was not possible to assess the relative influence of wild ungulates and livestock on water quality in different riparian habitats with the information currently available.
Determination of the relations between livestock and wildlife grazing and water quality can be approached using two different experimental designs: (1) comparison of multiple field sites with differing levels of wildlife and livestock grazing, or (2) controlled experiments with known kinds and numbers of animals held in confined areas.
Comparison of several sites to determine relations between grazing and water quality is not a reasonable approach to research due to several limitations, the most severe being the ability to measure the past and present grazing intensity without error. The most scientifically sound approach to determining the relations between livestock and wildlife grazing and water quality is the use of controlled experiments. Such experiments will require extensive funding and long time periods to complete, but they are the only feasible approach to obtaining sound information. State and federal agencies were contacted to identify potential field study sites and experimental sites for research. Thirty sites throughout the state were visited and evaluated according their potential as field or experiment sites. Seven field study sites and five experimental study sites were identified as potentially good areas to conduct future research.
Funding for this project was provided by the Wyoming Department of Environmental Quality (WDEQ), Cheyenne, Wyoming and the U.S. Environmental Protection Agency. Robert Gumtow (WDEQ) initiated the project and provided input throughout the study. Our appreciation goes out to the following people from various State and Federal agencies for their suggestions and showing of potential study sites throughout the state. Wyoming Game and Fish Department: Gary Butler, Charles Clarke, Huey Dawson, Mark Fowden, Robert Gurney, William Hepworth, Lloyd Harrison, Lynn Jahnke, Steve Kilpatrick, Ronald Lockwood, Daryl Lutz, David Moody, Vern Stelter, Richard Straw, Dan Stroud, Gary Thayer, Roger Wilson, Robert Yates, and James Yorgason. Bureau of Land Management: Thomas Ball, James Dunder, Jerry Jech, and Kenneth Stinson. U.S. Forest Service: Tim Dryar, Ray Keewit, Faith Ryan, and Kent Van. National Park Service: Norman Bishop, Roy Ewing, and Pete Hayden. U.S. Fish and Wildlife Service: Fran May, Tom Pabian, and Bruce Smith. University of Wyoming Range Department: Jerry Dodd, Mike Smith, and Quentin Skinner.
Special thanks go to Brian Heath, Mark McKinstry, and Evin Oneale of the Wyoming Cooperative Fish and Wildlife Research Unit for their help.
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