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Reference Conditions, Degraded Areas, Stressors, and Impaired Beneficial Uses: Conceptual Integration of Approaches to Evaluating Human-Related Environment Pressures

Jan J.H. Ciborowski 1, Jeffrey Schuldt 2, Lucinda B. Johnson 3, George E. Host 3,
Carl Richards 4 and Tom Hollenhorst 3.

1 Dept. of Biological Sciences, University of Windsor, Windsor, Ontario
2 Department of Biology, University of Wisconsin Superior, Superior, Wisconsin
3 Natural Resources Research Institute, University of Minnesota, Duluth, Minnesota
4 Minnesota Sea Grant, University of Minnesota, Duluth, Minnesota

Various models have been developed to provide a conceptual framework within which to classify areas and assess the effects of human activity on their environmental condition. We show that locations can be ordinated along independent hypothetical axes representing specific types of anthropogenic disturbance ('pressure' sensu SOLEC). The ends of an axis represent minimum and maximum pressure, respectively. Axes diverge from a common hyperdimensional point, representing the absence of pressure (pristine conditions). The Reference Condition is the suite of locations within a hypergeometric volume extending from the common point to locations along each axis at which the biotic community is meaningfully different than the community at the 'apex'. The diverging pressure axes form the edges of a pyramid, the base of which represents classes of "degraded condition". Correlation (r) between values of two different classes of pressure among locations define the angle of divergence of the axes (arc-cos[r]), hence pyramid shape.

A "pressure pyramid" of Great Lakes coastal margin habitats is derived using 5 GIS-based measures of human activity from the Great Lakes Environmental Indicator database of land use values relating to agriculture, natural land cover, distance from an NPDES point source, and population density in the 295 second-order or greater watersheds. Principal components analysis (PCA) ordinated the 295 sites on two principal component axes. A plot of eigenvectors of the 5 measures on the two axes shows the shape of the pyramid base. This pattern is analogous to a rosette diagram of the pressures imposed by human activity.

Keywords: Reference condition, stress, Great Lakes, coastal margin, integration, land use, multivariate

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