Invasions and impacts of exotic plants in the Pacific islands.
Islands support many more species of invasive plants than comparably sized mainland habitats. Analysis of extensive data on the distribution of invasive plants among Pacific islands suggests that the diversity of these species on islands is a function of both environmental characteristics (island size, habitat heterogeneity) and socioeconomic conditions (country identity, per capita gross domestic product, presence of airports with paved runways, human population size and density). The spread and impact of invasive species on islands also are likely affected by the juxtaposition of agroforestry operations and forest boundaries, by native floras whose competitive capacity is low and/or reduced by loss of pollinators and dispersal agents, and by the ability of some invasive species to alter ecosystem structure and function in fragile island landscapes. Islands also lack many of the necessary resources to respond effectively to the spread and impacts of invasive plants. Countries with more resources should be mindful of the potential impacts of exported species on small island ecosystems and seek ways to bolster resources of island governments in the management of invasive species.