Why the Coral Triangle is so species-rich
The Coral Triangle's extreme species richness is due, in part, to the wide variety and sheer acreage of habitats available for colonisation, specialisation and evolution. Three habitats are usually considered the "big three" for conservation because of their high productivity, ecological value and superlative biodiversity: coral reefs, seagrass beds and mangroves. Other important habitats include beaches, shallow mudflats, the open seas, deep trenches, migratory passages between islands, and seamounts.
The Coral Triangle contains at least 600 species of coral, which comprises around 75% of the world's coral species; more than 3,000 species of fish; six of the world's seven species of marine turtle; and more seagrass and mangrove species than anywhere else.
- 600+hard coral species — about 75% of all known species
- 3,000+reef fish species recorded
- 6 of 7of the world's marine turtle species
- #1globally for seagrass and mangrove diversity
Critically endangered hawksbill turtles nest throughout the Coral Triangle, with the largest populations nesting on several tiny islands in Indonesia, Malaysia and the Philippines. The western Pacific subpopulation of giant leatherback turtles nests on beaches along the island of New Guinea, in both Indonesia and Papua New Guinea, and in the Solomon Islands.
The region's waters are the most important spawning ground for several species of tuna. The only known population of coelacanths outside Africa was found off Indonesia's Sulawesi Island. The world's largest fish, the whale shark, can be found throughout the Coral Triangle, with regular seasonal aggregations at Donsol in the Philippines and Cenderawasih Bay in Indonesia.
Marine mammals are widely distributed across the region. Endangered dugongs occur in low numbers due to habitat loss and hunting. The world's largest animal, the blue whale, and the second largest, the fin whale, are frequently encountered in the seas of Indonesia and Timor-Leste.
The four habitat groups
Coral reefs
The defining habitat of the region and the basis of its name. Reef-building corals create the physical structure that everything else colonises, and the diversity of that structure is what allows so many species to specialise alongside one another. Reefs also absorb wave energy before it reaches the shore, making them the first line of coastal defence for thousands of low-lying islands.
Seagrass beds
Shallow meadows that stabilise sediment, act as nursery grounds for juvenile fish and invertebrates, and provide the grazing that supports the region's dugongs and green turtles. Seagrass attracts far less attention than reefs and is lost more quietly, usually to dredging, reclamation and sedimentation from land.
Mangroves
The Coral Triangle has more mangrove species than any other region. Mangroves trap sediment before it reaches the reef, buffer storm surge, store very large amounts of carbon in their soils, and shelter the juvenile stages of many commercially important fish and crustaceans, including the mud crabs that support a valuable regional fishery.
The open sea
The deep passages, currents and seamounts between the islands are migratory corridors for tuna, sharks, rays and cetaceans, and they are the mechanism that spreads coral and fish larvae between reef systems. The strong currents that make diving here demanding are the same currents that keep the region's reefs connected and able to recover.
Ten flagship species of the Coral Triangle
The flagship species concept holds that by raising the profile of a particular species, it can successfully leverage more support for biodiversity conservation at large in a particular context.
1. Sea turtles
The leatherback (Dermochelys coriacea), green (Chelonia mydas), hawksbill (Eretmochelys imbricata), olive ridley (Lepidochelys olivacea), loggerhead (Caretta caretta) and flatback (Natator depressus) sea turtles can all be found within the Coral Triangle. Of these six, four are listed as critically endangered by the IUCN, and international trade is strictly regulated under CITES. Human threats include consumption of eggs, hunting, fishery bycatch, inappropriate management practices, destruction or modification of nesting habitat, and pollution. Well-managed, limited access to some nesting beaches has been used successfully in eco-tourism projects in the Turtle Islands of Sabah, Malaysia.
2. Whale shark
The whale shark (Rhincodon typus) is the largest fish in the world. There are several locations within the Coral Triangle where feeding, and perhaps even mating, aggregations occur: Southern Leyte, Donsol, Pasacao and Tubbataha Reef in the Philippines, and Cenderawasih Bay in Indonesia. Whale sharks are completely harmless to humans; unfortunately the reverse is not true. Dried fins from almost all shark species, including the whale shark, fetch enormous prices as an ingredient for shark fin soup.
3. Dugong
The dugong (Dugong dugon), sometimes called the "sea cow", shares an ancestral line with elephants rather than with other marine mammals. Dugong populations in the Coral Triangle are in steady decline due to habitat destruction, fishery bycatch and hunting. While sightings are reported throughout the region, Palawan and the Tawi-Tawi island chain in the Philippines, along with the coast of Timor-Leste, are known to host slightly larger populations.
4. Humphead wrasse
The humphead wrasse (Cheilinus undulatus) is the largest of all wrasses and is usually spotted around coral reefs. The species has become rare in many parts of the Coral Triangle because of very large demand as a luxury dish in live reef food fish restaurants. Females can live more than 50 years, but juveniles are often taken from the wild and raised in floating net cages until they are large enough to sell.
5. Groupers
Many grouper species live in the Coral Triangle. Most are slow-growing and reach sexual maturity only after several years, and they are heavily targeted for their high value as live reef food fish. Spawning aggregations are especially vulnerable, since whole populations can be caught at once. The coral grouper (Cephalopholis miniata) is one of the more popular food species for its deep red colour, a sign of prosperity in some Asian cultures.
6. Manta and mobula rays
Manta and mobula rays are among the most charismatic species you can encounter in the Coral Triangle. The largest manta species can reach a wingspan of up to seven metres and a weight of 2,000 kg. They sometimes aggregate at cleaning stations or to feed in plankton-rich water. Threats come from accidental entanglement in long-line and net fishing gear, and from fishermen targeting them for food and for their gill rakers, which are used in traditional Chinese medicine.
7. Pygmy seahorses
Pygmy seahorses are extremely well camouflaged tiny fish that form close relationships with a host plant or animal, such as gorgonians or hydrozoans. Nine species are currently known, most described and named only within this century. Pygmy seahorses came to sudden fame through underwater photographers worldwide capturing and publishing images of them. They are threatened by too much attention from photographers and by general reef degradation, while their larger cousins are caught for the traditional Chinese medicine trade.
8. Sperm whale
Sperm whales are found throughout the Coral Triangle, with the most frequent sightings reported in the Savu Sea in Indonesia and around Timor-Leste. Males may reach 20 metres in length and have the largest brain of any animal on Earth. They are extreme deep divers, plunging to 2,000 metres and more in search of squid. Sperm whale hunting has a long tradition among natives of Indonesia, long before commercial whaling began in the 18th century; there are still villages in Flores practising seasonal whaling in the traditional way, with wooden boats and hand-thrown spears.
9. Mola mola
Also known as the ocean sunfish, the mola-mola is the most common of three species in the Molidae family and the largest bony fish on the planet, reaching more than 2,000 kg. It feeds primarily on jellyfish, but also on squid, sponges and crustaceans. Mola-mola are found in open water all over the Coral Triangle, usually by chance; around Bali, Indonesia, they visit cleaning stations and can be observed reliably during the cold-water upwelling season. The main human threat is entanglement in large commercial drift nets.
10. Anemone fish
Anemone fish, or clownfish, belong to the large family of damselfishes. The great majority of anemone fish species are found only in the Coral Triangle and adjacent countries. They are named for their symbiotic relationship with sea anemones, and may well be the most photographed fish on the planet. Their popularity with aquarium keepers makes them vulnerable to over-collecting.
Where to go next
- Threats to this biodiversityOverfishing, destructive fishing, climate change, pollution and the wildlife trade.
- Fisheries and food securityThe seven fisheries that feed and employ the region.
- Where to see itTen of the best dive destinations in the Coral Triangle.
- Coral Triangle overviewThe full picture: region, people, conservation and the economics behind it.
This page is part of the reference on the Coral Triangle, the richest marine region on Earth. Return to the homepage for the full overview of biodiversity, fisheries, conservation, tourism and the economics behind them.