Much of South Carolina’s outer coastal plain is dominated by a network of rivers, streams and creeks that have produced many smaller marsh islands or hammocks.  These non-barrier islands vary in size from a fraction of an acre to hundreds of acres.  A survey of these islands was undertaken to catalog their floral and faunal diversity from 2003-2007.  In total, 123 islands were visited across South Carolina’s coastal counties.  Islands were repeatedly sampled to collect observations of the flora and fauna across multiple seasons.  The total species richness of vascular plants, insects, birds, reptiles, mammals, and amphibians was calculated for each island and was related to each island’s total area to produce a series of species-area relationships (using both the absolute number of species and log transformations).  In South Carolina, human access to hammock islands smaller than 2 acres in size is limited to discourage activities that may lead to the degradation of these islands and their adjacent aquatic systems.  We calculated the total number of species of each group that would be included if all the islands under a given size were preserved.  The maximum island size for this threshold was varied between 1 acre and 20 acres.

Results/Conclusions

While strong positive relationships between island area and species richness were observed for each group, plant species richness was an equally robust or better indicator of faunal richness on an island (for each faunal group).  Our analyses also revealed that islands smaller than 2 acres collectively supported half of the avifauna, nearly half of the mammalian species, over one third of the insect species, and over a quarter of the observed plant and reptile species found across all hammock islands.  Ultimately, we demonstrate how prioritizing the conservation of islands of a given size or with specific traits may maximize the preservation of a target floral or faunal group on hammock islands in South Carolina.