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Influence of land use and landscape setting on the ecological status of J. David Allan

Summary: 187
Influence of land use and landscape setting on the ecological status of
J. David Allan
School of Natural Resources & Environment. The University of Michigan.
Ann Arbor, MI USA 48109. dallan@umich.edu
The development of bioassessment methods for lotic ecosystems, combined with advances in geographic information systems
and spatial analysis, has resulted in a rapidly expanding literature linking land use to river condition. Such studies provide evi-
dence that declines in forested land and increases in agricultural and urban land frequently are predictors of a degraded state of
the habitat and biota. However, further research should address a number of challenges to our current knowledge. Both linear
and non-linear relationships have been described, and it will be useful to know when to expect non-linear or threshold respon-
ses. Legacy effects, where historical impacts may be stronger than present-day impacts, may be common but can be difficult to
recognize. There is ample evidence that landscape factors influence lotic ecosystems across a wide range of spatial scales, but
the roles of near-stream vs. larger spatial scales can be difficult to separate. This is part of the larger issue that multiple, inter-
acting factors link landscape change to stream response, and the pathways or mechanisms are rarely identified. Natural and
anthropogenic gradients often co-vary, because human activities are most intense in certain landscape settings, making it diffi-
cult to determine how much of the variation in stream condition should be attributed to human actions. Finally, because bioas-
sessment methods are intended to detect impairment rather than diagnose cause, it is important to establish mechanisms that
more precisely link land-use activities to stream condition, in order to prescribe appropriate restoration action. Future research


Source: Allan, David - School of Natural Resources and Environment, University of Michigan


Collections: Environmental Sciences and Ecology