Coral reefs are exceptional underwater ecosystems, present in many regions of the globe. They cover approximately 284,300 km², or less than 0.1% of the ocean surface, but are home to more than 25% of the world's marine biodiversity. However, these natural wonders are not found everywhere. Their location is mainly determined by very specific environmental conditions.
1. Tropical and subtropical zones.
The majority of coral reefs are found in tropical and subtropical waters, between latitudes 30° north and 30° south. These areas have ideal water temperatures, usually between 23 and 29°C, which are necessary for corals to survive. Coral reefs thrive in shallow, clear, well-oxygenated waters.
Here are some of the main regions where coral reefs are found:
The Indo-Pacific region : This is the area with the most coral reefs in the world, accounting for about 75% of all reefs. It includes the Great Barrier Reef , located off the northeastern coast of Australia. At over 2,300 km long, it is the largest coral reef on the planet. The region also includes coral reefs in Indonesia, the Philippines, the Solomon Islands, and New Caledonia.
The Coral Triangle : This biodiversity hotspot spans Indonesia, Malaysia, the Philippines, the Solomon Islands, Timor-Leste and Papua New Guinea. This region contains the greatest diversity of corals and reef fish in the world.
The Indian Ocean : There are several notable reefs here, including those of the Maldives, Seychelles and Mauritius. These reefs, although more isolated, are of great beauty and are essential habitats for many marine species.
The Caribbean : This region is home to about 10% of the world's coral reefs. Caribbean coral reefs are located off the coasts of countries such as Mexico, the Dominican Republic, Cuba, and the Virgin Islands. The Mesoamerican Barrier Reef , which stretches from Mexico to Honduras, is the second largest coral reef in the world.
2. Reefs in French overseas territories.
France, thanks to its overseas territories, has nearly 10% of the world's coral reefs. These reefs are mainly found in the following regions:
French Polynesia : With reefs covering much of its lagoons and seas, French Polynesia is home to some of the largest and most diverse coral reefs in the world, particularly around islands such as Bora Bora, Tahiti and the Tuamotus.
New Caledonia : The coral reef of New Caledonia is classified as a UNESCO World Heritage Site. It is the second largest in the world after the Great Barrier Reef in Australia.
Reunion and Mayotte : These Indian Ocean islands also host coral reefs, although smaller in size. Mayotte's reefs surround almost the entire island, forming a sheltered lagoon.
Clipperton : This tiny, isolated atoll in the Pacific Ocean is home to a unique, though difficult to access, coral reef.
3. Cold water coral reefs
Although most reefs are found in warm tropical waters, some corals, called cold-water corals , thrive in more temperate or cold regions. They are found in the deep oceans, at higher latitudes such as the coasts of Norway, Scotland, and off the coast of New Zealand. These cold-water reefs are made up of corals that do not need sunlight to survive, unlike tropical corals that rely on photosynthesis to feed themselves.
Conclusion
Coral reefs are found primarily in tropical and subtropical waters around the world, including the Indo-Pacific, the Caribbean, and the Indian Ocean. French overseas territories, such as French Polynesia and New Caledonia, are also home to many of these valuable ecosystems. Although lesser-known, cold-water reefs also exist, providing a fascinating example of coral diversity. However, regardless of their location, coral reefs are all facing increasing threats from climate change, pollution, and overfishing.
Scientific sources:
Veron, JEN (2000). Corals of the World . Australian Institute of Marine Science.
Spalding, M.D., Ravilious, C., & Green, E.P. (2001). World Atlas of Coral Reefs . UNEP World Conservation Monitoring Centre.
Andréfouët, S., et al. (2008). Reefscape diversity of French Polynesia . Coral Reefs , 27(4), 999-1005.
