Southeast Asia has about 30% of the world’s reefs and is the centre of biodiversity for hard corals and most other reef animals and plants. The region is also experiencing rapid population increases and dynamic economic growth, concentrated mainly in coastal areas. Heavy reliance on the marine resources has resulted in non-sustainable use and degradation of many coral reefs. Most reefs close to major populations have deteriorated drastically. Some remote reefs may remain in pristine condition, but there are increasing threats from roving bands of fishers taking fish by destructive means, especially cyanide. Pressures will increase as accessibility improves and the demand for fish, especially for the live fish trade, expands with economic wealth. Countering this is a demand from marine tourism for untouched reefs, which can generate long-term sustainable income if managed carefully. Of 49 reefs monitored in five ASEAN countries, less than 20% had live coral cover in excess of 75%. Many of the reefs also showed a steady decline in live coral cover with time. In response, increasing numbers of marine protected areas are being gazetted throughout the region, but less than 10% maintain a high level of management. Awareness is expanding rapidly, but recent economic turmoil will mean that calls for conservation of reef resources may go unheard in the rush to return economies to growth.

Southeast Asia occupies only 2.5% of the ocean surface, but contains 30% of the world’s coral reefs, and links the Pacific and Indian Oceans. The reefs stretch across longitudes 93^oE to 141^oE and straddle the equator from 21^oN to 11^oS. There are over 25,000 islands, some just small dots, but there are also two of the world’s largest archipelagoes, Indonesia with more than 17,000 islands, and the Philippines with over 7000 islands. All reef types are common, including oceanic atolls, barrier reefs, and platform reefs, and many of the islands have fringing reefs.

Everything is favourable for reef growth — the right geology, oceanography, and climate, and there are only tropical storms at the higher latitudes in the Philippines, Thailand, and Vietnam. Many of the reefs are on the large Sahul and Sunda continental shelves; others fringe old volcanoes arising from deep oceanic waters. The richness of coral species is the highest in the world, and this is also the case for fish, molluscs, crustaceans, and echinoderms.

Direct and indirect human pressures now pose the greatest threat to Southeast Asian reefs. The population of 450 million today is expected to almost double to 716 million by the year 2025. The majority of these people live along the coast, and development pressures have caused the loss of many reefs, particularly those close to large populations. Most reefs show significant damage from over-fishing, pollution and sediment damage. Scientists in the region ranked sediment loading (due to dredging, coastal development and engineering, and coral sand mining) as the most serious threat, followed by nutrient pollution from sewage and agriculture, oil pollution, and industrial pollution. The fastest growing source of damage to all reefs, particularly the remote ones, is through over-fishing with dynamite, muro-ami (driving fish into fixed nets by bashing the coral with rocks and poles), and cyanide. In addition, unregulated tourism, coral mining, and nearshore trawling, have caused considerable damage to the reefs. All human impacts were ranked higher than natural impacts.

Fish are the main source of animal protein in the region, with reef fisheries contributing up to 30% of the total catch. Major food fish from the reefs include grouper (serranids), snapper (lutjanids and lethrinids), rabbitfish (siganids), fusiliers (caesionids), and mackerel, tuna, and carangids. Squid, cuttlefish, and molluscs are also taken from reefs. But there have been major declines in catches, indicating that many stocks have been depleted beyond sustainable levels. For example, reef fisheries in the Philippines once provided up to 36 tonnes per square kilometre each year, but the degraded reefs offer only 10–15% of this amount. In addition to food from the reefs, there is also a major curio trade in shells and corals, and in live animals for the aquarium trade, most of which are exported beyond the region.

This region has an excellent capacity to assess reef status and do reef research, which derives in part from the ASEAN-Australia Living Coastal Resources project in five ASEAN countries (Indonesia, Malaysia, the Philippines, Singapore, and Thailand) from 1984 to 1994. During this time, there were over 959 line-intercept survey transects, each 100 m long at 42 reef locations. The results showed that less than 3% of the reefs surveyed in Indonesia, Malaysia, and Singapore could be considered as ‘Excellent’, and assessments by experienced scientists suggested that there is a 70% increase in degraded reefs in the last 50 years, with productivity losses of up to 80%. Scientists reported a high diversity of fish species, with 307 species in the Philippines, 268 in East Indonesia, and 179 in West Indonesia. A lower diversity of species was found in East Malaysia (144), West Malaysia (118), Myanmar (86), Vietnam (83), Singapore (77), East Thailand (77), West Thailand (70), and Brunei Darussalam (38).

The strongest natural influence is the annual monsoon, which reverses current flows and introduces freshwater into coastal areas, lowering salinity and increasing sedimentation. Typhoons affect the Philippines, Vietnam, and Thailand, while volcanic and tectonic activity occurs in Indonesia and the Philippines. Isolated instances of Acanthaster plagues have occurred. Widespread coral bleaching occurred over many of the region’s reefs in the early half of 1998. This was triggered by elevated sea-surface temperatures connected to the El Niño phenomena.

The few coral reefs are offshore, because coastal areas are dominated by sediment-laden rivers. Coral cover is generally low for this region, with 40% at Pelong Rocks, and 27% at Two Fathom Rock. Brunei lays claim to part of the Spratly complex of reefs — Louisa Reef, 230 km off the coast. An initial study showed there were 88 coral species belonging to 52 genera.

Most of the reefs are in the southeast around the numerous islands of the Mergui Archipelago. The reefs have 65 coral species in 31 genera, but this may be an underestimate as few studies have been conducted. There are few natural stresses to these reefs, but human factors are known to be very high.

Very little is known of the few reefs around the offshore islands near Sihanoukville because of the lack of capacity, and persistent political turmoil in this region.

Fringing and patch reefs are common around most islands of the Indonesian Archipelago. Barrier reefs grow well along the edge of the Sunda shelf, east of Kalimantan, and around the Togian Islands of central Sulawesi, and in the deeper seas to the east. Taka Bone Rata, in the Flores Sea, is the third largest atoll in the world. Pulau Pulau Seribu, or Thousand Islands, form a spectacular chain of platform reefs with many coral islands out from the capital Jakarta. The count of 359 coral species from eastern Indonesia is an underestimate, as many new species have been discovered recently.

Tropical storms have little impact on Indonesian reefs, but rough seas and freshwater runoff from the two reversing monsoons each year do control reef growth in some areas. The 1983 El Niño event raised sea temperatures in the Java Sea and caused up to 90% coral mortality on the reef flats of many of the Seribu Islands. Five years later only half of the coral had recovered. Acanthaster damage has caused severe damage to some reefs, including the Seribu Islands, but no recent population outbreaks are known.

Reefs in western Indonesia are subject to greater human pressures than reefs in the east. For example, coral cover on almost 40% of the reefs in the Seribu Islands is ‘Poor’, and only 5% have ‘Excellent’ coral cover. There is considerable sediment and nutrient pollution coming out of the city of Jakarta, and from the many small tourist resorts on the islands. Subsistence fishing pressures are very high and fish catches have declined with loss of coral cover, for example catches decreased from 1350 tonnes in 1973 to 100 tonnes in 1990. In eastern Indonesia, 22% of the reefs were ‘Poor’, and 7% were ‘Excellent’. All reefs near centres of population suffer from human impacts, and now there are many roving bands of fishermen who are damaging remote reefs by fishing using dynamite, cyanide, and muro-ami methods. Indonesia has started a massive Coral Reef Rehabilitation and Management Project (COREMAP) aimed at safeguarding the country’s dwindling coral reefs, and slowing degradation. An economic analysis showed that the value of intact coral reefs to the Indonesian economy in tourism and sustainable fisheries was 50 times greater than the value obtained by using cyanide to collect fish, and mining coral rock and sand.

Most of the coral occurs as fringing reefs along the coast or around the offshore islands on the east coast of peninsular Malaysia with 55–70% coral cover on most reefs. Whereas there is much less growth on the west coast, with 25–45% cover, due to the higher concentrations of sediment. Fringing reefs are found on the coast of Sabah in East Malaysia, with much more around offshore islands, where there are also patch reefs. Live coral cover is between 43% and 52% with more dead coral and rubble than peninsular Malaysia, due to the common practice of blast fishing. The waters around Sarawak are muddy and contain a few poorly developed coral communities, but often have 60% live coral cover. The only true atoll is Layang-Layang in the Spratlys, where clear waters permit coral growth to a depth of more than 40 m, but cover on the upper slopes was naturally low at 29% because of oceanic waves. The recent development of a resort and airstrip caused a massive 75% loss of live coral cover. Over 350 coral species are found on Malaysian reefs, with Acropora the dominant genus.

Extreme low tides have killed corals on the east coast of the peninsula, while sporadic Acanthaster outbreaks have damaged most reefs, except those on the west coast of the peninsula. On these west coast reefs, there are seasonal blooms of macroalgae, because the large amount of development has caused much sediment and nutrient pollution. Fishing pressures are very high in east Malaysia, and there is regular use of blast and cyanide fishing techniques. The government has declared a number of islands as MPAs and this is having a beneficial effect to conserve corals and fish.

Most of the reefs, which cover an estimated 25,000 km², are fringing reefs and vary in length from tens of metres to 5 km. The largest concentration is in the southwest. The best of the Philippine reefs are the two atolls in the Sulu Sea (Cagayancillo and Tubbataha), the atoll-like formations (like Apo Reef near Mindoro Island and Scarborough reefs west of Luzon), and the banks west of Palawan (one of the largest barrier reef areas in the world). A double-barrier reef grows on the Danajon Bank off Bohol, and a few more small barrier reefs are also present. There have been 499 species of hard corals reported from the Philippines.

Surveys showed that only 3.6% of the reefs in Luzon were in ‘Excellent’ condition, while 27% had less than 25% coral cover. In the Visayas near the middle, 6.6% were in ‘Excellent’ condition, while 31% were ‘Poor’; and in the far south in Mindanao, 5.3% were in ‘Excellent’ condition and 49% ‘Poor’. Recent surveys show that there may be some recovery as there is a greater proportion of live coral cover compared to dead coral.

Typhoons cause extensive damage to northern reefs, such as at Mactan, while Drupella and Acanthaster infestations have caused significant local damage. The eruption of Mt. Pinatubo in 1990 resulted in massive flows of ash onto reefs of western Luzon. This caused a 23% to 69% decline in fish biomass on reefs along the coast of Zambales, along with a drop in live coral cover. Human impacts are, however, far more damaging. More than 80% of Philippine tropical forests and mangroves have been cleared, resulting in massive amounts of sediment flowing onto the reefs. There is virtually no treatment of domestic and industrial wastes, which mostly flow into the sea. Over-fishing has caused considerable damage to all reefs, both coastal and offshore. Because of the high level of poverty and large numbers of fishermen, most reefs have been stripped of fish that are easy to catch with lines, traps and nets. Now fish are being caught using destructive methods like muro-ami, home-made bombs, and cyanide. The rich trade in live fish for restaurants in Hong Kong has meant that large reef fish are virtually extinct on most Philippine reefs, with fishermen able to take fish from as deep as 40 m using compressed air.

Giant clams were once abundant but were virtually wiped out from many reefs through over-fishing. Brood stocks were imported for clam hatcheries in Bolinao and Dumaguete, and juvenile clams are being used to restock Philippine reefs, and provide an income for local fishers. The Philippines is one of the largest exporters of live and dead coral, and other species such as anemones, for the aquarium trade. This has also contributed to the decline in Philippine reefs.

The Philippine government has been active in encouraging local level management of coral reefs, and there are a few outstanding examples of success. The best known is Apo island off southern Negros, and many other examples of management of reef resources are developing around the country. Successful national parks have been established for the Tubbataha reefs in the Sulu Sea and the El Nido reefs of west Palawan, however, over-fishing at El Nido is causing damage to these tourist reefs.

All of the reefs are around the southern offshore islands, where more than 197 hard coral species in 55 genera are known. The area is relatively sheltered and on the equator, therefore damage from tropical storms is negligible. No Acanthaster have been recorded. However, about 70% of Singapore reefs are now degraded compared to the pristine condition 50 years ago. Recent data indicate a further decline in live coral cover on the upper slope of the better reefs (76% in 1989 to 69% in 1993). The major cause of reef degradation is sedimentation brought about by four decades of land reclamation, dredging of navigational channels, and dumping of dredged materials further out to sea. Reef slopes below the depth of 6 m support little live coral cover compared to the early 1960s when water was clearer and coral growth extended to 10 m. Many of the reef conservation measures are initiated by nongovernmental organisations (NGOs), and increased awareness has brought about the creation of a ‘marine nature area’ by the government in 1996. This area encompasses six islands, all with fringing reefs.

There are over 300 major reef groups covering an estimated area of 12,000 km² divided into four areas: i) inner part of the Gulf of Thailand (Chonburi); ii) east side of the Gulf (Rayong and Trad); iii) west side of the Gulf (Prachuap Kirikhan, Chumporn, and Surathani); and iv) along the Andaman Sea coastline (Ranong, Phuket, Phang-Nga, Krabi, Trang, and Satun), where about 55% of Thailand’s reefs occur. The best reefs are in the provinces of Trad, Phang-Nga, and Trang, and the majority are fringing reefs, though there are many coral communities growing on rock as well. Over 60% of all major reef groups in Thailand have less than 50% live coral cover and there is increased algal growth because of nutrient pollution from the land, including near the major tourist resorts of Pattaya Bay, Phuket, and Ko Samui.

Storms and monsoon waves are the major natural causes of coral reef damage. Typhoon Gay hit southern Thailand in 1989 and caused major damage to some reefs. Localised outbreaks of Acanthaster have been reported in the Gulf of Thailand, and an increase in infestations has occurred in the Andaman Sea since 1982. Extreme low tides and coral bleaching are other natural phenomena causing severe damage. Like all countries of the region, sediment and nutrient pollution from development on the land is causing major damage to the reefs, along with significant over-fishing. Thailand has many large trawlers, which are now fishing close to reefs, causing damage. Much of Thailand’s mangrove forests have been cleared for prawn ponds and timber, such that the natural sediment traps have been removed.

There is an active NGO network in Thailand, which is assisting communities with local management of coral reefs, and restoration of forests and mangroves.

Reefs that cover 400 km² occur along the 3200 km coastline of Vietnam, mostly around 3000 islands on the shelf and offshore. There are no reefs around the deltas of the Red and Mekong Rivers. There are five sub-regions with more than 300 hard coral species, but not all areas have been surveyed: i) reefs to the west of Tongkin Bay and Gulf have coral cover from 30% to 50% with 165 coral species; ii) central Vietnam; iii) in southeast Vietnam there are 176 species including the Con Son Islands off the southern tip, which are particularly rich in species; iv) west of south Vietnam (Gulf of Thailand) there is between 30% and 40% cover and 138 species; and v) the offshore islands and atolls in parts of the Spratlys claimed by Vietnam, have the highest coral diversity (188 species).

Storms and typhoons, and low winter temperatures are the major natural stresses, and sediment runoff and pollution because of rapid economic development, are causing damage to the inshore reefs. The offshore reefs are being damaged by fishing activities including trawling, the use of dynamite and cyanide, and over-fishing. Vietnam commenced its Marine Conservation Project in 1992 aimed at managing marine resources, including coral reefs.

In most areas, live coral cover should be high (>50%) because there are few tropical storms, so the major factors determining coral cover are human disturbance. Data are from the ASEAN-Australia Living Coastal Resources project on transects usually at 3 m and 10 m depths on the reef slope. Condition values refer to percentage of transects with coral cover of Excellent >75%; Good <75->50%; Fair <50->25%; and Poor <25%.

Many reef management systems exist in the region and numerous marine protected areas (MPAs) have been established in Southeast Asia. But many of these exist only on paper with no staff or operational funding. About 10% of the 106 MPAs established in the ASEAN countries are effectively managed, and few staff are adequately trained in park management and lack the enforcement resources to control damaging activities. There is poor coordination and communication between agencies managing different parts of the coast, and resulting conflicts are undermining conservation and protection efforts. There is a need for increased political commitment to conserve Southeast Asia’s coral reef resources.

Community-based management is achieving better success using a range of different models, particularly in the Philippines and Thailand. Community management of local areas provides better motivation to manage the resources that communities depend on, and results in effective control of destructive activities. Co-management between government agencies, local communities, and NGOs is more effective for larger areas.

Many Southeast Asian countries have signed international conventions and agreements like the Convention on Biological Diversity, and the Convention on International Trade in Endangered Species (CITES). These have been effective in slowing the export of live and dead corals from the region. A number of informal agreements, such as the 1989 Langkawi Declaration on the Environment, the 1990 Baguio Resolution on Coastal Resource Management, the 1990 Kuala Lumpur Accord on Environment and Development, and the 1994 Bangkok Resolutions on Living Coastal Resources, demonstrate increased awareness about managing coral reefs for sustainable use.

Southeast Asian reefs have been heavily exploited during in the last 30 years, with economic growth and population increases causing the collapse of about 11% of the reefs. A further 48% are in the critical category, with collapse likely within the next 20 years, if management commitments are not met. Policy makers now know that managed reefs provide sustained benefits, but government bureaucracy and inter-agency conflicts prevent effective management beyond the declaration of MPAs. The best way to conserve coral reefs is through integrated coastal management, but Southeast Asian countries are still a long way from adopting national conservation policies. Short-term development overrides the need for sustainable development and adherence to international agreements.

Implementing an action agenda to conserve these high biodiversity reefs is urgent, and the agenda must gain full support from all sectors of government, users, and the public. Effective coral reef conservation requires that local users and officials are informed and involved in sustainable resource management, backed up by excellent legislation, planning, and enforcement by governments. The current rate of reef degradation can only be reduced when there is better understanding of reef functions and the need for MPAs. If human pressures can be reduced, reefs in oceanic waters should recover rapidly, because there is a ready supply of larvae and clean water, but reefs on the continental shelves close to polluted areas will not recover fully until the pollution buried in the sediments is washed out.

Professor Loke Ming Chou is from the Department of Biological Sciences of the National University of Singapore.