The richest coral seas on Earth, shared by six nations and containing about 76% of all known coral species.
The Coral Triangle spans Indonesia, Malaysia, the Philippines, Papua New Guinea, the Solomon Islands and Timor-Leste — six countries share this scientific sea, and Indonesia and the Philippines hold much of the reef without being the whole triangle. Inside about 1.6% of the global ocean, regional assessments report about 29% of coral reefs, 76% of known coral species and 37% of reef-fish species.
More than 120 million people live in the region and depend on its marine resources. The Triangle is more than fish over coral: coral animals build with algal partners, while seagrass meadows and mangrove roots extend living habitat toward shore.
The Bird's Head of New Guinea holds the Triangle's highest documented coral richness — that is Raja Ampat's corner, not every Triangle reef. A single well-surveyed Raja Ampat reef can hold more fish species than the entire Caribbean — the Triangle's richest corner, not every Triangle reef.
The tiny clownfish begins life as a male, and the largest one can later turn into the group's female.
A ram-feeding whale shark can filter roughly 326,000–614,000 litres of seawater per hour.
The Coral Triangle contains about 29% of the world’s coral reefs.
Coral animals build with algal partners, while seagrass meadows and mangrove roots extend living habitat toward shore.
The mimic octopus can reshape its body to copy sea snakes, lionfish and flatfish to fool predators.
Field Notes
The Richest Coral Seas
Across six nations the Triangle holds about 76% of known coral species, 37% of reef-fish species and 29% of the world's coral reefs, inside about 1.6% of the global ocean. Indonesia and the Philippines hold much of that reef, but they are not the whole triangle.
The Bird's Head of New Guinea holds the highest documented coral richness in that region — Raja Ampat's celebrated corner, not a claim that every Triangle reef matches it. A single well-surveyed Raja Ampat reef can hold more fish species than the entire Caribbean — the Triangle's richest corner, not every Triangle reef.
Research Report
Reefs Built by Tiny Builders
Every reef here is built by coral polyps — soft animals no bigger than a grain of rice. Each polyp shares its body with tiny algae that catch sunlight and make food, which gives coral its bright colours.
Millions of polyps grow their stony cups side by side over centuries to build a reef. These reefs then become homes: clownfish shelter inside stinging anemones thanks to a mucus coat and careful acclimation, and schools of hammerhead sharks patrol the deeper water, sweeping their wide heads to sense hidden prey.
Expert Dossier
A Nursery for the Ocean
The Coral Triangle supports exceptionally diverse coral and reef-fish communities. Nursery habitats are stacked: mangroves and seagrass raise young fish before they move onto the crest, extending living habitat from shore toward the reef.
Whale sharks filter-feed in tropical seas, while giant tritons prey on crown-of-thorns starfish. Coral animals build with algal partners on the crest, so the nursery belt and the reef builders belong to one connected shore-to-crest system.