A freshwater conservation assessment of the Upper Mississippi River basin using a coarse- and fine-filter approach


Mary Khoury, The Nature Conservancy, Great Lakes Project, 8 S. Michigan Ave., Suite 2301, Chicago, IL 60603-3318, U.S.A. E-mail: mkhoury@tnc.org


1. We identified priority sites for freshwater conservation in the Upper Mississippi River (UMR) basin using a coarse- and fine-filter approach to defining biodiversity elements as building blocks. Fine-filter species included federally listed threatened and endangered, imperilled, declining, endemic, disjunct and wide-ranging species. We had species data for over 1300 individual occurrences of species and communities identified as fine-filter elements. The coarse-filter elements are ecosystems (‘Aquatic Ecological Systems’) defined using physical attributes of streams and lakes, and stratified to represent key zoogeographical and physiographical gradients.

2. We used relative ecosystem integrity, species population viability and expert opinion to generate an initial ‘portfolio’ of 600 freshwater areas of biodiversity significance representing the best examples of the species and ecosystem elements. Representation targets were met for all ecosystem types and for an average of 45% for species groups.

3. The application of a coarse- and fine-filter approach to identify biodiversity conservation priorities in the UMR demonstrates the contribution of each component – even in an area with relatively rich fine-filter data. For a large assessment area, data, even if plentiful, will be uneven, and community-level diversity is not catalogued. Thus, the coarse filter allows for greater confidence that a broad suite of species and key environmental gradients are captured in a conservation portfolio, while fine-filter data provide greater confidence that species of conservation and management interest are addressed adequately.