- Coastal sand dunes are susceptible to invasive plants that significantly alter these endangered ecosystems. Acacia saligna is a small Australian tree that has become a significant invasive plant in Israel and in many other Mediterranean countries. The aim of this research was to study the impact of A. saligna on the indigenous vegetation of three coastal habitats (sand dunes, inter-dune depressions, and aeolianite [sandstone] ridges) in the Nizzanim Long Term Ecosystem Research Nature Reserve, Israel. Plant observations were conducted in the spring, in the following site types: (1) sites planted with A. saligna and sites invaded by A. saligna; and (2) reference sites not invaded by A. saligna. A simple index, the aggregate ecological value, was developed in order to evaluate the impact and the ecological value of each habitat and site for conservation purposes. The results indicate that planting A. saligna and invasion by A. saligna changed plant community composition, reduced psammophyte species richness, caused the disappearance of most endemic, rare, and protected species, and overall reduced the ecological value of the Nizzanim Nature Reserve.