Coral reefs are home to a third of all known marine species. About 8% of the world's human population lives within 100 km of a coral reef and tens of millions of these people depend on the productivity of coral reefs for their protein (IUCN 2009). Coral reefs shield thousands of kilometres of coastline from wave erosion, and protect lagoons and mangroves, which are vital habitats for diverse commercial and non-commercial species. A number of medically active compounds are derived from corals and associated reef species. The value of coral reefs for ecotourism is enormous. In total, the economic value of coral reefs probably amounts to several hundred billion dollars per year (IUCN 2009).