Coral reefs are one of the most threatened ecosystems in the world.
Rivaling terrestrial rainforests in their biological diversity, and providing major economic benefits from fisheries and tourism, coral reefs ecosystems are of global concern. While these problems still persist, the last two decades have seen the emergence of yet another, potentially much greater threat. Coral reefs have been affected, with increasing incidence and severity, by coral bleaching, a phenomenon associated with a variety of stresses, especially increased sea water temperatures, which when severe and prolonged can lead to widespread coral mortality. Coral reefs are among the most important marine ecosystems, providing food, serving as habitat for other commercial species, supporting the tourist industry, supplying sand for beaches, and acting as barriers against wave action and coastal erosion. Ironically, the worst bleaching has taken place in countries with the least capacity and resources to address it, and with the greatest need for healthy reefs as a contribution to sustainable development.