An Index of Cumulative Disturbance to River Fish Habitats of the Conterminous United States from Landscape Anthropogenic Activities

Reversal of widespread fish habitat degradation in the conterminous United States will require effective spatial planning, which begins with spatial assessment of current habitat conditions. We present an assessment of cumulative anthropogenic disturbance to fish habitats in approximately 2.23 million U.S. river reaches under the assumption that downstream local habitat conditions will reflect conditions in the catchment upstream. We used geographic information systems data to attribute 15 disturbance variables to the catchments of mapped river reaches to calibrate an index of cumulative disturbance that considered effects originating from both local and upstream catchments. The influence of each variable was adjusted in the index based on the results of multiple linear regression analyses of all variables against percent intolerant fishes at a site—a commonly used biological indicator of habitat condition. Urban landscape indicators were weighted most heavily, followed by point-source pollution, pasture lands, and dam densities. Local factors were found to be less influential on fishes than those originating from the upstream river network. Skewed cumulative disturbance scores indicated that disturbance levels of some reaches far exceeded the national median. Future assessments should include stratification of analyses within regions, expanded use of response metrics and datasets, and alternative analytical approaches to help tease apart the influences of interacting landscape disturbance types. We demonstrate how our results can be visualized and used to make regional comparisons among large-scale planning units and also show how reach-level information about upstream versus local disturbance levels can be used to identify potential habitat management strategies that are suitable to different landscape contexts.