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Coral Triangle

Ecoregion of Asia–Pacific

  • 10 min read
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Through Coral, Ecoregion and Indian Ocean

The World Wide Fund for Nature considers the region a top priority for marine conservation, and is addressing ecological threats to the region through its Coral Triangle Program, launched in 2007. One of the centers of biodiversity in the Triangle is the Verde Island Passage in the Philippines. The coral reefs in the region that have been declared UNESCO World Heritage Sites are the Tubbataha Reef Natural Park in the Philippines and the Raja Ampat UNESCO Global Geopark in Indonesia.

Biodiversity

While it covers only 1.6% of the planet's oceanic area, the region has 76% of all known coral species in the world. As a habitat for 52% of Indo-Pacific reef fishes and 37% of the world's reef fishes, it contains the greatest diversity of coral reef fishes in the world More than 3,000 species of bony fish are distributed over more than 90% of the Coral Triangle. Among the largest of these fish are the whale shark, the coelacanth and the chimaeras.

The Coral Triangle is the epicentre for the biodiversity, not only of corals and fish, but also of many other marine organisms. It contains roughly 950 species of Molluscs and 458 crustacean species. It is also the habitat for six of the world's seven marine turtle species.

Thirteen percent of the Coral Triangle has been identified as being clustered into hotspots of high marine biodiversity importance, including the southern part of the Philippines, the north-eastern part of Sabah in Malaysia, the central to eastern zones of Indonesia, the eastern part of Papua New Guinea and the Solomon Islands. The parts of the Coral Triangle that have the highest number of species comprise 6% of the triangle's total area. They include stretches along the coast of the Philippines (including the northern coast of Luzon, Bohol, Mindanao, Palawan, and the Sulu Archipelago), Malaysia (the northeastern coast of Sabah), Indonesia (the northern and southeastern part of Sulawesi, the Banda Sea, Maluku Islands (the Mollucas), and the Raja Ampat Archipelago of Indonesian Papua), Papua New Guinea (the coastal areas of Madang Province, New Britain, Milne Bay, the Louisiade Archipelago, and Bougainville Island), and the Solomon Islands (Guadalcanal and Makira-Ulawa Province). However, more than half (70%) of the zones in the Coral Triangle are classified as low species richness areas.

The sites of highest marine biodiversity importance in the Coral Triangle include: (1) the northern tip of Sulawesi, (2) Ambon Island, (3) Kai Islands (also Kei Islands), (4) Raja Ampat Archipelago of Indonesian Papua, (5) the Verde Island Passage in the Philippines, (6) the southern part of Negros in the Philippines, and (7) Cebu in the Philippines.

The greatest extent of mangrove forest in the world is also found in the Coral Triangle. These forests' large area and extraordinary range of habitats and environmental conditions have played a major role in maintaining the staggering biodiversity of the Coral Triangle.

The Coral Triangle countries comprised a minimum of 10 to a maximum of 19 seagrass species that belong to four distinct families (Hydrocharitaceae, Cymodoceaceae, Zosteraceae, and Ruppiaceae) and cover almost 58,550.63 km2. While a total of 21 species of seagrass have been found throughout this eco-region.

A joint Indonesian–U.S. marine survey expedition in 2008 discovered deep-sea biodiversity and underwater active volcanoes at a depth of 3800 meters along the western ridge. Around 40 newly identified deep-sea coral species were found there. Most are whitish in color, because the area is not a habitat for colorful algae species, which are generally shallow-living. Hydrothermal vents and coral reefs at a depth of 4000 meters were found to have created a habitat for marine niche shrimps, crabs, barnacles, and sea cucumbers.

According to Indonesia's Minister of Research and Technology / National Research and Innovation Agency (Menristek / Head of BRIN), Bambang Permadi Soemantri Brodjonegoro, Coral Triangle countries are in need of a greater number of taxonomists and oceanographers to address the challenges of cataloguing the biodiversity in the area. He has said that goal of this research is not only to increase human knowledge, but also to apply that knowledge to the project of protecting coastal and marine biodiversity from extinction.

Theories behind high species diversity of the Coral Triangle

There are three different theories as to why the Coral Triangle (East Indies Triangle) has such a high diversity of species, and each theory proposes a different explanatory model. They are usually termed the "centre of origin" model, the "centre of overlap" model, and the "centre of accumulation" model.

  • The centre of origin model posits that the high diversity populations in the area of the archipelago are part of a centrally located ancestral population that later dispersed to various peripheral locations.
  • The centre of overlap model posits that species originally in different biogeographic regions came together as a result of population division (vicariance) and later expanded their range.
  • The centre of accumulation model posits that ancestral populations that were originally scattered among peripheral locations came together in a central location and formed a diverse population.

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