Coral reefs can be found in more than a 100 countries and cover 112,000 to 4 million km2 depending on whether we consider reefs in the strict sense of the word or if we also include the lagoons they surround. The Great Barrier Reef (Australia) is the world’s largest coral reef system (350,000 km2). France has 55,000 km2 of them spread out over its 3 surrounding oceans, Indonesia has 51,020 km2, and the Philippines 25,000 km2.
These ecosystems protect the coasts from erosion caused by waves, serve as nurseries for young fish (particularly fringing reefs, which are the most threatened), and are a source of protein for local populations. They generate work and are the main source of support for small-scale fishing and tourism. In warm waters, 70% of coral reefs are threatened by climate change as well as direct effects of human activity: sewage and land runoff, tourist boats and diving, material removal and fishing practices.