EXAMINATION OF SALT MARSH DIEBACK DEVELOPMENT AND RECOVERY WITH THE USE OF HISTORICAL AERIAL PHOTOGRAPHY AND ENVIRONMENTAL AND CLIMATIC CONDITIONS

Tidal marshes are one of the most valuable ecosystems on the planet as they provide habitats for various marine life species, protect developed coastal areas from flooding, erosion, hurricanes/tropical storms, and improve the water quality of coastal wetlands. Since 2001, Georgia tidal marshes have experienced major losses in vegetation Previous studies suggest that climatic factors including temperature and precipitation pattern changes, sea level rise, drought index increase, and river discharge changes contribute to salt marsh dieback onset. Historical high quality aerial imagery is suitable for mapping changes in dieback extent over a certain time period. We collected aerial imagery dating back to 1999 showing three study sites located on the Georgia coast. Each individual image was exported into Environment for Visualizing Images (ENVI) for digitizing the boundaries between dieback and vegetation at two different spatial resolutions (1m, 2m) at a 1:500 map scale. The digitized polygons were then exported into ArcMap for area calculation. We also collected quantitative climatic data dating back to 1999 and conducted regression analyses to analyze the relationships between climatic conditions and the spatial extent of the dieback areas for 2003 and 2012. Preliminary results show one study site with a proportional change in dieback area of 5.0, the second with a change of 1.0, and the third with a change of -0.03. They also show that increase in drought index, combined with increase in air temperature is most effective in triggering salt marsh dieback. Further investigation is needed for the remaining years of the study period.