The overall objective is multifold, which includes identifying the major drivers for upland LULC change, which mostly likely fall into population growth, food requirement, and economic development; and assessing the impact of upland LULC change and sea-level rise on coastal wetland change respectively and simultaneously at the end of the century, therefore provide scientific information on the roles of regional land use / land cover (LULC) change and global sea-level rise in shaping coastal ecosystems.
Sea-level rise due to global warming coupled with regional and local land use / land cover (LULC) change poses great threats to coastal ecosystems. Accelerating wetland loss is one of them. Wetlands are valued for reducing storm surge, storing floodwater, protecting shorelines, improving water quality, recharging groundwater aquifers, and providing habitats for wildlife including plants, birds, fishes and oysters etc. (Ozesmi and Bauer, 2002) in addition to their recreational opportunities and aesthetics functions (Barbier et al., 1994). However, wetlands are usually drained or altered to create more land for agricultural use or urban, and commercial development. Canal, levee, and dam construction has contributed to the loss or alteration of wetlands by reducing the sediment and freshwater inputs and preventing wetland migration. Migration rates of wetland may not be able to keep up with sea-level rise, which will result in a net loss of wetlands from flooding. Other adverse impacts due to sea-level rise include coastline retreat, saltwater intrusion (Warne and Stanley, 1993; Martin et al., 2000; Day, 2005) and declines in net primary productivity (Day et al., 1997; Martin et al., 2000). The coastal wetlands of Mississippi Sound, St. Louis Bay, Biloxi Bay, Pascagoula Bay, and the tidal Pascagoula River provide critical nursery areas for many species of fish and shellfish. Menhaden and shrimp, the most important commercial species, depend on estuarine wetlands for protection and food when they are juveniles (http://www.nmfs.noaa.gov/habitat/habitatconservation/publications/habitatconections/num4.htm), last access on December 24 of 2007). However, Mississippi’s coastline is undergoing significant development. By the mid-1980’s, Mississippi had lost approximately 59% of its wetlands.
Identifying the major cause of the wetland loss will assist development of a more informed restoration strategy and prediction of future habitats. However, distinguishing different anthropogenic causes is difficult, and they vary in their impacts on wetland losses depending on geographical locations. Turner (1997) examined four hypotheses about causes for the high coastal wetland losses in Louisiana and concluded that most of the wetland loss was caused by the effects of canal dredging. Day et al. (2000) and Gosselink (2001) argue against the conclusion. Day et al. (2000) pointed out that wetland loss in the Mississippi River delta is an ongoing complex process involving several interacting factors and that efforts to create and restore Louisiana’ coastal wetlands must emphasize riverine inputs of freshwater and sediments in addition to mitigating canal dredging. Therefore, just like tropical forests, wetlands are disappearing as the result of many pressures, both local and regional, acting in various combinations in different geographical locations (Geist and Lambin, 2002).
No studies have shown that sea-level rise is a major cause for coastal wetland loss. However, the impact of sea-level rise cannot be ignored and it will certainly play a more important role in the long term as global warming complicates the issue of wetland loss.