CLIMATE-CHANGE, HURRICANES AND TROPICAL STORMS, AND RISING SEA-LEVEL IN COASTAL WETLANDS

Global climate change is expected to affect temperature and precipitat ion patterns, oceanic and atmospheric circulation, rate of rising sea level, and the frequency, intensity, timing, and distribution of hurri canes and tropical storms. The magnitude of these projected physical c hanges and their subsequent impacts on coastal wetlands will vary regi onally. Coastal wetlands in the southeastern United States have natura lly evolved under a regime of rising sea level and specific patterns o f hurricane frequency, intensity, and timing. A review of known ecolog ical effects of tropical storms and hurricanes indicates that storm ti ming, frequency, and intensity can alter coastal wetland hydrology, ge omorphology, biotic structure, energetics, and nutrient cycling. Resea rch conducted to examine the impacts of Hurricane Hugo on colonial wat erbirds highlights the importance of longterm studies for identifying complex interactions that may otherwise be dismissed as stochastic pro cesses. Rising sea level and even modest changes in the frequency, int ensity, timing, and distribution of tropical storms and hurricanes are expected to have substantial impacts on coastal wetland patterns and processes. Persistence of coastal wetlands will be determined by the i nteractions of climate and anthropogenic effects, especially how human s respond to rising sea level and how further human encroachment on co astal wetlands affects resource exploitation, pollution, and water use . Long-term changes in the frequency, intensity, timing, and distribut ion of hurricanes and tropical storms will likely affect biotic functi ons (e.g., community structure, natural selection, extinction rates, a nd biodiversity) as well as underlying processes such as nutrient cycl ing and primary and secondary productivity. Reliable predictions of gl obal-change impacts on coastal wetlands will require better understand ing of the linkages among terrestrial, aquatic, wetland, atmospheric, oceanic, and human components. Developing this comprehensive understan ding of the ecological ramifications of global change will necessitate close coordination among scientists from multiple disciplines and a b alanced mixture of appropriate scientific approaches. For example, ins ights may be gained through the careful design and implementation of b road-scale comparative studies that incorporate salient patterns and p rocesses, including treatment of anthropogenic influences. Well-design ed, broad-scale comparative studies could serve as the scientific fram ework for developing relevant and focused long-term ecological researc h, monitoring programs, experiments, and modeling studies. Two concept ual models of broad-scale comparative research for assessing ecologica l responses to climate change are presented: utilizing space-for-time substitution coupled with long-term studies to assess impacts of risin g sea level and disturbance on coastal wetlands, and utilizing the moi sture-continuum model for assessing the effects of global change and a ssociated shifts in moisture regimes on wetland ecosystems. Increased understanding of climate change will require concerted scientific effo rts aimed at facilitating interdisciplinary research, enhancing data a nd information management, and developing new funding strategies.