Rising sea level tends to increase the salinity of both surface and ground water

Rising sea level would allow saltwater to penetrate farther inland and upstream.  The resulting saltwater intrusion could harm aquatic plants and animals, as well as threaten human water supply (IPCC 1998).  Salinity has been found to decrease seed germination in a variety of wetland species and to decrease recruitment of seed bank species (Baldwin et al 1996).  Already, higher estuarine salinity has been cited as a cause of declining oyster harvests in Chesapeake and Delaware Bays, and as a cause of wetland loss in Louisiana, Florida, and Maryland, and in Louisiana, cypress swamps are becoming open lakes due to increasing salinity (IPCC 1998).  Increasing salinity could cause an up-estuary advance of marine and estuarine species and a retreat of freshwater species.  Some species now thriving in the waters of the lower estuary would migrate into the upper estuary (DRBC). 


Wetland loss, salinity changes and higher temperatures are likely to affect biota in coastal areas

Rising global temperature may cause waters in many areas to become too warm for the fish that currently inhabit those areas. Warmer temperatures may enable fish in cold ocean waters to grow more rapidly.  Global warming may also change the chemical composition of the water that fish inhabit.  For example, the amount of oxygen in the water may decline, and pollution and salinity may increase.  Also, the loss of wetlands could diminish habitat and alter the availability of food for some fish species.  Warming causes the range of some species to shift north, their food webs are altered and their habitats are lost.  From 50 to 70 percent of Atlantic coast commercial fish species depend on estuaries and tidal marshes which form the nurseries for fluke, flounder, striped bass, bluefish, weakfish, and the horseshoe crab.  Estuaries and marshes are also the adult living space for blue crab, oysters, and forage species (Climate Alert 1997).

Nearly 100 species of migratory waterfowl, marsh, and shorebirds, or colonial species spend a portion of their life cycles in marshes (Erwin).  Sea level rise affects birds in many of their activities: breeding, foraging, and migrating.  An increase in water level brings more competition among species as they fight for dwindling space.  It leads to flooding at high tide, killing nesting species.  If beaches are eliminated, so is the egg-laying of horseshoe crabs, the food base of many birds (Climate Alert 1997).  As marshes are reduced in area, marsh-specialist birds will find lower quality habitats in the remaining fringe marshes; these fringe marshes are susceptible to invasion by predators such as raccoons, foxes, cats, and dogs.  However, losses of nesting habitat for ducks and colonial species may be partially compensated for in some species by increases in feeding habitat (Erwin).

Coastal forests are shrinking in size as salinization of ground and soil water increases with sea level rise.  In the Florida Keys, there has been a reduction in the area of forests dominated by pine and an increase in the presence of halophytic species in former pine forests.  Pine mortality is related to topographic position with pines dying earlier at lowest elevations.  Areas of earliest pine mortality are now populated by a higher proportion of halophytic plant assemblages.  If sea level continues to rise, the Keys will experience a decline in both landscape and species diversity, as species-rich upland communities are replaced by simpler mangrove communities (Ross et al 1994).  This patter may also occur in other low-lying island ecosystems with limited freshwater resources (Williams et al 1999).

        Sea level rise affects the rate of sedimentation

Highest rates of sedimentation will occur at higher elevations on the marsh and less sedimentation will occur on the lower elevations.  Varying sedimentation rates will result in changes in vegetation zonation and succession on marshes (Olff et al 1997).