Although the timing and magnitude of global climate change is in dispute, the possible effects of such change merit consideration to allow for discussion of policy ramifications and mitigative actions. Climate change may result in sea level rise; water temperature increase; and deviations from present patterns of precipitation, wind, and water circulation. Estuaries may experience loss of marsh habitat, intrusion of marine waters and associated organisms, changes in circulation patterns that affect retention of some indigenous species, and increased hypoxia and storm surges. Estuarine and coastal systems could experience poleward retreat of cold-tolerant species and range expansion of warm-tolerant species. Some fisheries and aquacultural enterprises and communities would benefit from the results of climate change and others would suffer losses, with economic and population dislocations probably inevitable in many parts of the world. Thus, flexibility in policy-making and planning will be vital if global climate is modified as rapidly as is anticipated by some scientists.