Impacts of Intensive Rotational Grazing on Stream Ecology and Water Quality

Impacts of Intensive Rotational Grazing on Stream Ecology and Water Quality

Summary

This report summarizes preliminary findings of the second field season. Riparian areas on livestock farms provide important habitat for wildlife and fish communities and a filter for pollutants, in addition to providing water for livestock. Rotational grazing, which provides environmental as well as economic benefits, is a relatively new option for dairy farmers. It may be a reasonable compromise between continuous grazing and fencing livestock out of riparian areas. We are currently completing our second season of data collection, which compares three management options for riparian areas on small- and moderate-sized farms: ungrazed buffer strips, rotational grazing and continuous grazing, on more than 20 private farms along trout streams in southwestern Wisconsin.

Adjacent land use is a major factor of streambank stability and instream and terrestrial habitat quality. Many differences among treatments are due to the fact that the buffer strips are not harvested. Buffer strips had significantly taller and denser vegetation than rotational and continuous pastures. Streambank stability and instream habitat were the best for the buffer strips, but rotational pastures were not significantly different from buffer strips and were superior to continuously grazed pastures. Preliminary results suggest that fish and aquatic invertebrate communities respond more to watershed scale differences than adjacent land use. None of the treatments had consistently healthy cold water fish communities. Buffer strips averaged the best overall with more trout and fewer warm-water fish species. Rotational pastures had habitat conditions similar to grassy buffer strips, but fewer trout. Continuous pastures had poor instream habitat quality and poor cold-water fisheries. Riparian wildlife communities appear to respond to local and landscape scale habitat factors. Grazed riparian areas may be more suitable for amphibians and birds than buffer strips, while small mammals were more numerous in buffer strips than pastures. Greater species diversity of birds was observed in rotational and continuous pastures than in buffer strips, although absolute numbers were similar. Grassland bird species occurring in both pastures included eastern meadowlarks, savannah sparrows, brown-headed cowbirds, killdeer, song sparrows, red-winged blackbirds and American goldfinches. Species diversity and abundance were greater adjacent to the stream than in upland counts.

Dairy producers in this region are facing an economic climate which necessitates change. This research will document the environmental consequences of two very different options farmers are considering. Preliminary results suggest that IRG may provide a good compromise between fencing and continuous grazing of riparian areas, providing water quality protection and wildlife habitat benefits. Large herd confinement dairying presents unknown, potentially large environmental risks. We will clarify environmental consequences of these options and guide both farmer and agency decision-making. North Central Region SARE 1997 Annual Report.