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NATURE OF CUMULATIVE IMPACTS ON BIOTIC DIVERSITY OF WETLAND VERTEBRATES
Citation:
Harris, L. NATURE OF CUMULATIVE IMPACTS ON BIOTIC DIVERSITY OF WETLAND VERTEBRATES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-88/501 (NTIS PB90186156), 1990.
Description:
There is no longer any doubt that cumulative impacts have important effects on wetland vertebrates. he interactions of species diversity and community structure produce a complex pattern in which environmental impacts can play a highly significant role. ariety of examples shows how wetlands maintain the diversity of vertebrate populations, and some of the ways that environmental perturbations can interact to reduce this diversity. The concept of the trophic and habitat pyramid, from most specialized to least specialized organisms. is a useful organizing principle. abitat fragmentation can have severe effects at all levels, reducing the usable range of the larger, habitat generalists and threatening the genetic integrity of small. specialized populations. he complexity of trophic interactions, and the propensity, or necessity, of vertebrates to switch from one food source to another, a subject about which we have insufficient information, makes the use of food chain support as a factor in predicting environmental impacts very questionable. Effects of the accumulation of impacts on vertebrates are illustrated by a number of historical examples. At present it appears nearly impossible to predict the result of three or more different kinds of perturbations, although the long-range effects can be observed. ne such case includes the ingestion of lead shot by waterfowl, harvesting by hunters during migration, and loss of habitat. aterfowl populations have declined, but the proportional responsibility of these factors has not been determined. Further examples show the multiplicative effects of similar actions, effects with long time lags, diffuse processes in the landscape that may have concentrated effects on a component aubsyatem, and a variety of other interactions of increasing complexity. ot only is more information needed at all levels; impacts will need to be assessed on a landscape or regional scale to produce informed management decisions. ystem of replicate wetland reserves that are allowed to interact naturally with the surrounding landscape will be more effective in preserving biotic diversity than isolated sanctuaries.
