VII. Aquatic Conservation Links

Non-sustainable land-use practices and nonpoint source pollution are principal causes of the widespread decline of the biological and functional integrity of aquatic ecosystems over broad areas of the United States (Allan and Flecke r 1993, Karr et al. 1986). It is widely believed that many of the adverse effects of human activity at the landscape scale can be mitigated by protection of the riparian corridor at the land-water interface (Sweeney 1992, Osborne and Kovacic 1993). However, the benefits conveyed by a vegetated riparian are not well understood, particularly from the standpoint of instream habitat quality and biological integrity. Based on preliminar y evidence from studies of a largely agricultural Midwestern watershed, land use at the watershed scale is a better predictor of stream ecosystem degradation than are riparian measures.

We propose a two-year study in the River Raisin, a 2776 km2 agricultural and urbanizing watershed in southeastern Michigan, to determine the characteristics and extent of riparian vegetation throughout the watershed, and to evaluate the protective benefit s of various riparian configurations including Best Management Practices (BMPs) from the perspectives of soil loss and biological integrity. Our four objectives are: 1) complete a land-use and land-cover analysis for the entire watershed and sub-watershe ds of the River Raisin, using a Geographic Information System (GIS); 2) extensively characterize the riparian region of all tributaries and the mainstem of the river; 3) assess the effectiveness of various riparian management practices on stream ecosystem health through measures of biotic integrity and instream habitat quality; and 4) compare the effectiveness of existing and potential alternative riparian management practices on delivery of sediments and nutrients to aquatic ecosystems, using spatially-r eferenced models.

By meeting the four objectives described in the proposal, we expect to be able to answer specific questions and test hypotheses concerning the effects of land use, riparian condition and instream physical habitat on the functional and biotic integrity of stream ecosystems, and develop a predictive model relating these elements. These results, from a watershed typical of the lower Midwestern U.S., will contribute to USDA's ability to assess the effects of agricultural practices on the functional integrity of aquatic ecosystems.