In the early part of the 20^th century Carex kobomugi, Asiatic sedge, was introduced to New Jersey and is now widespread on the coastal dunes. This study focused on the Sandy Hook Unit of Gateway National Recreation Area. Using differential GPS the affected areas of the dune communities were mapped.  GIS technology was used to depict the affected areas and to investigate patterns of individual plant species’ presence /absence, as well as species richness and species diversity in affected and unaffected areas of the dune system. Quadrat counts of plant species identity and abundance were also carried out. Five-meter buffer zones surrounding the areas colonized by C. kobomugi were also examined and used to compare native species richness and diversity changes.   Native plant diversity and species richness in unaffected areas was greatest in areas farthest from human impact, and decreased in areas of greater human impact. Invasion by C. kobomugi decreased native species abundance, species richness and species diversity in this park. This effect was strongest in the areas of the park where species richness and diversity in unaffected areas was at its highest (areas farthest from human impact).