Abstract: Coastal hammock vegetation in the Thousand Islands (TI) is associated with two pre-Columbian shell middens, named Provost and Salmela Hammock. These middens provide a source population of tropical and subtropical coastal hammock species for recruitment to islands modified by dredge spoil during mosquito control efforts and housing development in the late 1950s through early 1970s. Significant recruitment has taken place in some dredged areas. I suggest that this coastal hammock community be considered a viable restoration goal following removal of invasive non-native vegetation in the TI.

I will add a handout when completed, and a draft of the manuscript as soon as it is submitted for publication. Additionally, I evaluated vulnerability to sea level rise using LiDAR data from St Johns River Water Management District. LiDAR is a method in which a LASER is used to map topography. The image below is a LiDAR map of Provost hammock with the vertical exaggerated by a factor of 25 times.
 

With the digital elevation model it is possible to do all sorts of cool things with data. I took 86 GPS points at the very edge of the hammock where the upland vegetation was replaced by wetland species. I used a special type of GPS with differential correct to achieve sub-meter accuracy. Using a type of software called GIS (Geographic Information System) I extracted the elevations of each point and averaged them, taking into account the inaccuracy of the GPS and LiDAR. Unfortunately the LiDAR data is in the dreaded English system so the units are “feet.” The hammock began at an elevation of about 1.5 feet above sea level. It’s then a simple matter to use the GIS to eliminate land area below a specified elevation and graph the results in Program R. The resulting graph is below.

Obviously, the news here is not good. The heavy lines are the average, red is Salmela hammock, the blue Provost, and the black is the entire Thousand islands. The faint lines are the 95% confidence intervals to give a range for the uncertainty in the vertical and horizontal measurements. A sea level rise of 20 cm (roughly ten inches) destroys about 80% of the hammock. Sea level rise expected by the middle of this century essentially obliterates the Thousand Islands.