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Effects of livestock grazing in southern interior wetlands: interactions with amphibians, benthic macroinvertebrates, vegetation, and breeding waterfowl
Jones, W. Marc
Livestock grazing can be a significant human stressor on wetlands. In regions with widespread livestock use, such as the southern interior of BC, understanding how grazing pressure affects wetland function is crucial to effective wetland management. Wetlands in the Thompson-Okanagan and the Chilcotin-Cariboo are important habitat for migratory birds, but they are also recognized for their natural forage production by the cattle industry. British Columbia produces approximately 5% of Canada?s beef cattle, a disproportionate share in relation to B.C.?s human population, and half of B.C.?s beef cattle are produced in the southern interior (20). In addition, it has been estimated that approximately one-half of the grazed forage and stored winter feed is produced on wetlands in this region (20). Southern Interior wetlands occur primarily within a landscape mosaic of forests and grasslands. Wetlands provide numerous environmental and economic benefits, including wildlife habitat, regulation of water regimes, filtration of polluted water, and production of forage crops (13). The importance of these benefits, especially in semiarid regions, is disproportionate to the extent of wetlands on the landscape. Given the amount of wetland losses over the past century, the importance of remaining wetlands has become even more critical. Previous research has shown that grazing can affect the structure and function of wetland ecosystems. Grazing can alter wetland water quality, biodiversity, and productivity directly, through removal of biomass, soil compaction and trampling, and nutrient inputs, as well as indirectly by changing plant competitive interactions through selective herbivory and nutrient loading (5,8,11,12,15,17). Grazing influences on some taxa, such as waterfowl, may be primarily mediated through changes to vegetation or invertebrates that alter their habitat and food webs. Maintaining the biodiversity and productivity of wetlands (and thereby sustaining their habitat and forage production values) requires understanding how grazing influences these complex interactions. This research has two components: 1. Sample depressional wetlands in the interior Douglas-fir and bunchgrass biogeoclimatic zones along a grazing intensity gradient, and measure associated changes in water quality, wetland vegetation, amphibians and benthic macroinvertebrates. We will then evaluate whether grazing-related changes to vegetation and macroinvertebrates influence breeding waterfowl. 2. Evaluate changes to wetland-related biota (benthic macroinvertebrates, amphibians and vegetation) and water quality associated with off-site water development. In coordination with the Agriculture Canada Kamloops Range Research Unit and BC Parks, we will provide four freshwater wetlands in Lac du Bois Provincial Park that are currently heavily used by livestock with an adjacent off-site water source. There is anecdotal evidence that cattle prefer hardened surfaces when accessing water and that off-site water development can reduce trampling effects of cattle in wetlands (Don Thompson, pers. comm.). The off-site water source will consist of a trough provided with water from the wetland through either gravity feed or solar pump. Two wetlands will be completely fenced. Changes in wetlands biota and water quality will be monitored over time. Other goals of this research are to identify the natural range of variability of response variables associated with minimally disturbed wetlands and to identify thresholds of biotic and physical variables associated with grazing disturbance. This proposal requests funds to expand an existing multiyear research project funded by Ducks Unlimited Canada (Western Region and the Institute for Wetland and Waterfowl Research). In the first year of the project (2006), we measured vegetation communities and waterfowl use, primarily, and preliminary results show a very strong response of vegetation structure and composition to grazing intens ...
Report Number
Executive Summary
Annual Progress Report
Effects of Livestock Use... (Presentation)

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