Mapping salt marsh dieback and condition in South Carolina’s North Inlet-Winyah Bay National Estuarine Research Reserve using remote sensing

摘要

Marsh dieback, or brown marsh, occurs when areas of salt marsh vegetation either thin or completely die. The exact extent and locations of marsh dieback are often unknown due to the difficulty accessing salt marshes for in-field observations. Remote sensing provides a synoptic view of earth surfaces and helps to highlight vegetation thinning or loss covering large spatial areas. In 2002–2003 there was a marsh dieback event that affected South Carolina. While most research focused on causes of the event, its extent has not been mapped. Using satellite data to extract the normalized difference vegetation index (NDVI) for years between 1999 and 2003, this study calculated the change in vegetation greenness of the North Inlet salt marsh in Georgetown, South Carolina. Results showed where the marsh vegetation increased or was lost/thinned. The northern section of the marsh experienced the most vegetation decline, while the southern end of the mash experienced a gain in vegetation. The region with the least amount of vegetation decline occurred within mid elevations of the marsh. It is likely that the vegetation within higher elevations experienced stress due to hypersalinity, while vegetation within the lower marsh experienced stress from hypoxia leading to increased rates of vegetation decline in these zones. The elevation of marshes in the northern section is low, and a significant decline in NDVI there may signal a decline in marsh health due to rising sea level.