This paper highlights the seriousness of the “biodiversity crisis” on atolls and the need to place greater research and conservation emphasis on atolls and other small island ecosystems. It is based on studies over the past twenty years conducted in the atolls of Tuvalu, Tokelau, Kiribati, the Marshall Islands and the Tuamotu Archipelago of French Polynesia. It stresses that atolls offer some of the greatest opportunities for integrated studies of simplified small-island ecosystems.