Carex kobomugi (Asiatic sand sedge) is an invasive dune species that was accidentally introduced to the United States in the early 1900s. Since then it has expanded rapidly, and is now commonly found along the dunes of Island Beach State Park, New Jersey. Using differential GPS, all stands of Carex growing in the park were mapped in summer, 2003. Using GIS those maps were combined with data on species diversity and richness from quadrant counts in order to investigate the effect of Carex kobomugi on native plant abundance and diversity. Even in the absence of Carex, dune communities in this park showed relatively low species richness and diversity. In areas where Carex was found, the abundance of most native plant species was reduced relative to non-invaded areas. However, since few species appeared to be completely eliminated, presence of Carex often had no effect on species richness and diversity. Indeed, in some cases, areas invaded by Carex actually had significantly higher species richness and diversity.