Conservation status of forests and vertebrate communities in the Vava'u Island Group, Tonga

Based on field work in 1995 and 1996, we assess the distribution, relative abundance, and habitat preferences of forest plants, lizards, birds, and mammals on 17 islands in the Vava'u Group, Kingdom of Tonga. The islands vary in habitat composition, land area (0.02-96 km²), elevation (20-215 m), and distance (0-10.1 km) from the largest island of 'Uta Vava'u. Two major forest types are recognized - coastal and lowland. They are similar in composition to forest communities described for the southern Tongan island group and for lowland Samoa, but with unique patterns of species dominance. The most mature category of lowland forest persists mainly in areas too steep for cultivation and covers about 10% of the land area. The greatest variation in plant species composition appears to be related to the degree of human disturbance. Among lizards, six species are widespread and at least locally common, whereas three others are localized and typically rare. Among landbirds, 11 species are widespread and at least locally common, one (West Polynesian Ground-Dove Gallicolumba stairi) is extremely rare, and three others have been extirpated in the past century. The overall species richness and relative abundance of indigenous plants and vertebrates among islands in Vava'u have been affected more by deforestation and other human activities than by the classic physical variables of island biogeography - area, elevation, or isolation. Small islands (<1 km²) may be very important for conservation purposes, especially given the propensity for secondary succession to indigenous forests following agricultural abandonment.