As climate change proceeds, evaluating the environmental impacts emerges as a global priority. The current rate of sea level rise, 2-3 mm/year along many US coastlines, is predicted to accelerate with continued global warming. Coastal dune ecosystems protect coastlines from erosion by stabilizing and accreting sandy soils that mitigate sea surge from daily tides, episodic storms and tsunami events. As they protect the interior they are poised to bear the first impacts of the rising sea. Maritime influence on soil hydrology impacts the function of numerous terrestrial coastal ecosystems, however global warming is also predicted to redistribute rainfall making it vital to understand the delicate balance between fresh and ocean water in order to predict how dune ecosystems will respond to future climate change. The purpose of this study is to investigate the influence of ocean water on soil and vegetation of coastal dunes. Three coastal dune systems, a barrier island off the coast of southern Florida, and two islands in the Bahamian bank/platform system were investigated.
The results of this dissertation indicate the impacts of sea-level rise on coastal dunes will be exacerbated by decreased rainfall. Fore dunes (5-12m inland) at 2 of the three study sites were vulnerable to ocean water intrusion; the vulnerability is most pronounced in the dry season and intensifies with decreasing annual precipitation. Several plant species uptake ocean water during periods of intrusion, showing signs of physiological stress. Ocean water intrusion is not detected on inland dunes (35-50 m inland), however most plants are rainfall dependent in this area when the elevation precludes groundwater recharge to the upper soil layers. Therefore decreased precipitation presents a second threat to the dune ecosystem sustainability by limiting water availability to higher elevation dunes.