GIS-BASED VULNERABILITY MODELING OF SOUTH CAROLINA MARSH HAMMOCKS AND ASSOCIATED SPECIES TO SEA LEVEL RISE
McCalley, Matthew Owen
Gramling, Joel M
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Hammock islands are low-elevation landforms in coastal marshes that host high biodiversity. Global sea level rise projections over the next century are at levels that will likely inundate many hammock islands. This analysis modeled the effects of accelerated sea level rise (SLR) to 226 hammock islands under three SLR scenarios and provided unique methods for DEM calibration and hydrologic connectivity modeling. The influence of two- and three-dimensional spatial parameters on hammock island species richness was assessed. LiDAR modeled changes in the strongest parameters were used to predict post-SLR species richness. The model indicates that collective island area is reduced by 27.42%, 59.02% and 74.07% for 52 cm, 82 cm and 1.0 m SLR scenarios, respectively. All modeled islands incurred inundation for at least 7% of the island's surface area. 91.6% of islands were >/=50% affected, 56.8% of islands were >/=90% affected and 29.2% of islands incurred complete inundation under the 1.0 m SLR scenario. The variables most strongly associated with species richness were the area of an island (r-squared=64.18) and the volume of an island above mean high water (r-squared=72.81). The relative change and magnitude of change for islands and associated species differed depending on island size. Applying changes in island volume to the predictive function indicated a 2.29%, 10.55% and 17.63% decrease in quartile-derived collective species richness for SLR at 52 cm, 82 cm and 1.0 m, respectively; post-SLR island area indicated an 8.33%, 21.50% and 30.67% decrease in collective species richness respective to the same SLR scenarios. SLR may potentially interact with South Carolina's marsh island regulation, as island size will change over the next century. Conservation efforts must harness active management to promote in-situ habitat resilience at the local scale while urging global greenhouse gas reductions.