Sea level rise, salt water inundation, and hurricane driven disturbances are known to have numerous effects on coastal vegetation and the distribution of plant communities. As climate change drives sea level rise, small oceanic islands like the islands of the Florida Keys may be drastically affected as they lack the buffering ability of large land masses and are especially confounded by episodic events, such as hurricanes, and the accompanying storm surges. Our study compared plant communities on the halocline between mangrove and upland habitat, in terms of both structure and composition, and made direct comparisons with data, collected 10 and 20 years before. During 2013-14, we resampled 25 transects in the National Key Deer Refuge to determine changes to hardwood trees and the herbaceous layer. In particular, we studied the presence of rare and endangered plant species after documented sea level rise and storm surge. We hypothesized that as a result of increased salinity, species richness should decline as fewer species are adapted to such conditions, and that the proportion of salt-tolerant species within the community increased over the last 20 years.
Results/Conclusions
The Florida Keys are low lying islands with little elevation and are susceptible to inundation. During the time period of this study, sea levels have risen approximately 15cm (2 mm per year). The results suggest drastic changes in the ecosystem as salt tolerant plant species dominate and indicate a loss of biodiversity, especially rare and endemic plant species as densities have significantly declined in the study area over the past 20 years. In almost all instances, the percent of salt tolerant species increased from 20 and 10 years go. As salt tolerant plant species increase over time, we also document a significant decrease in species richness and in total coverage of specific plant species (Borrichia frutescens, Fimbristylis spadicea, and Spartina spp.), important to the survival of marsh rabbits. Understanding vegetation community changes through time in response to rising sea levels and more frequent storm surges will lead to a better understanding of the effects of stochastic events as well as provide guidance for management practices to protect rare and endangered species and important habitat for the animals dependent on declining plant species.