Cumulative impacts have important effects on wetland vertebrates. The interactions of species diversity and community structure produce a complex pattern in which environmental impacts can play a highly significant role. A variety of examples shows how wetlands maintain the diversity of vertebrate populations, and some of the ways that environmental perturbations can interact to reduce diversity. It is impossible to predict the result of three or more different kinds of perturbations, although the long-range effects can be observed. One such case includes the ingestion of lead shot by waterfowl, harvesting by hunters during migration, and loss of habitat. Waterfowl 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 subsystem, and a variety of other interactions of increasing complexity. Impacts will need to be assessed on a landscape or regional scale to produce informed management decisions. A system 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. (Copyright (c) 1988 Springer Verlag.)