Islands in the tropical Pacific have a rich and unique biota produced by island biogeographic processes and modified by recent anthropogenic influences. This biota has been shaped by four overlapping phases: natural colonization and dynamics (phase 1), impacts of indigenous (phase 2) and non-indigenous (phase 3) settlers, and increasing environmental awareness (phase 4). Island ecosystems are resilient to natural disturbance regimes but highly vulnerable to invasive species and other human-related influences, due to comparatively low alpha diversity, isolated evolution and the absence of certain functional groups. Habitat loss, overexploitation, invasive alien species and pollution continue to threaten terrestrial biodiversity, compounded by limited environmental awareness, minimal conservation funding, project mismanagement, limited local capacity and inadequate and/or unsuitable conservation policies. To achieve effective conservation of terrestrial biodiversity in the region, biophysical threats need to be mitigated with improved scientific, institutional and management capacity.