Chapter 2: Biodiversity of Southeast Asian coral reefs
Southeast Asia's coral reefs have the highest degree of biodiversity of all the world's coral reefs. This extraordinarydiversity generates high productivity, providing food for millions of people within the region and beyond. Scientists are just beginningto understand the potential diversity of coral reefs; it is estimated that only 10 percent of marine species associated with coral reefshave been identified and described.
The epicenter of global marine biodiversity
Scientists have found more coral species around a single island in Southeast Asia than have been identified for the entire Caribbean.[1] The map below, which shows coral reef diversity worldwide, illustrates the high concentration of species in the region, particularly in the broad Indo-Malayan Triangle, stretching from the Philippines to the southern islands of Indonesia and encompassing all of Java east to New Guinea. This extraordinary diversity has built up over geological timescales, but it is maintained through the wide array of physical conditions-salinity, wave exposure, depth, temperature, and turbidity-found across Southeast Asia that fulfill the requirements of a broad range of species.[2] The region contains more than 600 of the nearly 800 reef-building coral species (Scleractinia) found worldwide.[3]
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The diversity of coral reefs is not limited to coral species. Over 1,650 fish species have been recorded in eastern Indonesia alone, the majority of which are associated with reefs.[4] This same diversity is also found in related coastal ecosystems. Southeast Asia contains over 61,000 square kilometers of mangroves, approximately 35 percent of the world's total. It holds nearly 75 percent of the world's mangrove species and over 45 percent of seagrass species.[5]
Setting priorities for conservation
Few coral reef areas in Southeast Asia remain unaffected by human activities. In the past, reefs in remote locations were relatively pristine. However, isolation is no longer a guarantee of good reef condition, as evidenced by the degradation of reefs in the Morotai Islands (North Maluku).[6] Even reefs in good condition like the Spratly Islands, Tubbataha, and eastern Indonesia are threatened by human activities such as destructive fishing practices. The reefs that are still largely unaffected by people may be particularly important to the survival of species and the recovery of neighboring areas. Relatively "pristine" reefs not only harbor a diverse suite of corals and fish, but they also provide an important source of larvae for degraded reefs.
Active management and protection are key to maintaining the ecological integrity of the region. Priority areas should include not only places that have high species richness but also locations that contain a broad diversity of habitat types or unique species or assemblages. The location of protected areas should also consider factors of connectivity between reefs.
Many conservation organizations are developing and applying prioritization schemes for marine conservation, typically focusing on biodiversity. The Reefs at Risk threat indicator makes it possible to integrate socioeconomic considerations and human pressures in prioritization efforts.
Notes
1. C.C. Wallace, "Journey to the Centre of the Centre: Origins of High Marine Faunal Diversity in Central Indonesia from the Perspective of an Acroporologist," Plenary speech, 9th International Coral Reef Symposium, Bali, Indonesia, October 24, 2000; and T. Tomascik et al., The Ecology of Indonesia, VIII: The Ecology of the Indonesian Seas. Part Two (Oxford: Oxford University Press, 1997).
2. J.E.N. Veron, Corals in Space and Time: The Evolution of the Scleractinia (Ithaca, NY: Cornell University Press, 1995).
3. Calculated at United Nations Environment Programme (UNEP) and World Conservation Monitoring Center (WCMC), based on data from J.E.N. Veron and Mary Stafford-Smith, Corals of the World (Cape Ferguson: Australian Institute of Marine Science, 2000).
4. D. Hopley and Suharsono, eds., The Status of Coral Reefs in Eastern Indonesia (Townsville, Australia: Global Coral Reef Monitoring Network, 2000), p. 3.
5. Mangrove information from M.D. Spalding, F. Blasco, and C.D. Field, eds., World Mangrove Atlas (Okinawa: The International Society for Mangrove Ecosystems, 1997), pp. 44-73. Seagrass information from United Nations Environment Programme-World Conservation Monitoring Centre, Seagrass Database (Cambridge: UNEP-WCMC, unpublished.)
6. Hopley and Suharsono, The Status of Coral Reefs in Eastern Indonesia, p. 19.
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