The Use of Remote Sensing to Assess Salt Marsh Dieback

Abstract

Salt marshes are invaluable to coastal communities, providing carbon sequestration, habitat, and mitigation from storms. All along the Eastern Atlantic seaboard, salt marsh vegetation has been experiencing diebacks. While the cause of these diebacks is presently unknown, studies have made links to climate change-related factors, such as temperature increase, drought, and sea level rise. This study used remote sensing techniques to access the relationships between vegetation loss within the Blackwater National Wildlife Refuge and several climate-related variables. The reflectance of the vegetation was isolated using a normalized difference vegetation index (NDVI) and square kilometers of vegetation cover were measured for each year from 2003 to 2018. Image transformations allowed the subtraction of one year’s vegetation cover from another, providing a change in vegetation over time with a total percent loss of vegetation of 0.32%. There was a positive correlation between vegetation loss and time (r(15) = 0.547, p = 0.014). Additionally, there was a positive correlation between vegetation loss and river discharge when lag time was added to vegetation loss (r(14) = 0.494, p = 0.031). No other significant relationships were found between marsh loss and the following variables: air temperature, surface water temperature, sea level, and elevation.