Wetlands preservation has recently become a favored cause of conservationists. Protection of wetlands is justified primarily on grounds of their beneficial biological and hydrological effects, so it is to the physical sciences that government and the public turn for the formulation of management policies. But scientific knowledge cannot be translated directly into good resource policy for society. Despite growing scientific sophistication, we are limited in our ability to understand and to predict the effects of man‐induced change on natural systems, especially ones as complex as the Chesapeake Bay and its associated wetlands.