Hotspots on Global Coral Reefs

Coral reefs represent the pinnacle of marine diversity, but are seriously threatened by human activities. Coral reefs reach highest diversity in the Indo-Australian archipelago, with secondary peaks in the southwestern Indian Ocean and West Atlantic. Diversity declines into the Central Pacific, is lower in the East Pacific than in the Caribbean for most (not all) taxa, and is lowest in the East Atlantic. Endemism varies with scale – local endemism shows no significant geographic pattern, but regional endemism is high in the Indo-Australian archipelago, moderate in the western Indian Ocean and Central Pacific, and highest in the Americas, especially the East Pacific. Among all studies, species diversity correlates significantly with average threat (local impacts, ocean warming and acidification, bleaching, disease, inadequate protection), but neither local nor regional endemism correlates with threat or diversity. When diversity, endemism, and threat are combined to form local hotspots, Indonesia, the Philippines, New Caledonia, the islands of southern Japan, and southeastern Africa merit highest conservation attention. Regionally, especially the Indo-Australian archipelago, but also the East Pacific, the Caribbean, greater Australia, and the western Indian Ocean deserve highest current conservation priority. However, projected mega-scale environmental changes such as ocean warming and acidification pose particular challenges and may alter how we set regional priorities in the future. We conclude with a discussion of the controversies surrounding coral reef hotspots and their possible resolution.