Foredune Texture: Landscape Metrics and Climate

Coastal dunes are sensitive ecosystems because of their location at the juncture of terrestrial, marine, and atmospheric environments. This is especially the case for foredunes and the vegetation they support. Considerable attention is paid to the characteristics of foredunes and dune vegetation, but there has been no systematic study of patterns of bare sand on foredune surfaces—foredune textures—and the climate variables controlling those patterns. We used landscape metrics to quantify foredune textures for twenty-two coastal locations in the contiguous United States and cluster analysis to classify textures using those metrics. Four types of texture were identified: (1) active, where bare sand averages more than 80 percent of the dune surface and sand patches are close together; (2) composite, with about 50 percent bare sand area and sand patches that are close together and of minimal complexity; (3) aggregated, where bare sand is about 23 percent of the surface and the sand patches are moderately adjacent, of relatively low complexity, and relatively far apart; and (4) inactive, where the bare sand averages about 6 percent of the surface and the patches are complex in shape and widely spaced. These types are discernible using four climate variables. We used those variables to derive multiple regression models to predict key landscape metrics and use Intergovernmental Panel on Climate Change climate predictions to forecast changes in foredune textures through the twenty-first century. We find that vegetation cover should increase at 82 percent of our sites.