Relating landscape development intensity to coral reef condition in the watersheds of St. Croix, US Virgin Islands

Abstract

Land-based sources of pollution are a major threat to the health of coral reefs. We report, for the first time, a study that relates coral reef condition to human modifications of the landscape. Stony coral community richness, cover, colony size, and density were assessed along with 3-dimen- sional coral cover in the near-shore waters of St. Croix, US Virgin Islands, in 2006 and 2007. Land use/land cover data (LULC, 2.4 m resolution) and a landscape development intensity (LDI) index, an indicator of human activity calculated from the LULC data, were used to explore relationships with coral indicators. The LDI index was more robust than other indicators of human activity, exhibiting negative correlations with stony coral colony density, taxa richness, colony size, and total coral cover. High variability observed in coral density and taxa richness was better explained when percent nat- ural land and average coral station depth were considered along with the LDI index. Percent imper- vious surface in the watershed was negatively correlated with 1 coral condition indicator, total coral cover. The LDI index is an effective landscape indicator of human impact on St. Croix corals, high- lighting the link between land-based human activity and marine ecosystems. Further development of this tool will aid in land use planning and prioritization of conservation efforts.