Summary | Threats to Coral Reefs | Industrial Pollution | Sedimentation | Overfishing | Oil Spills | Maps | References | Credits
Over 30% of the world's coral reefs are found in Southeast Asia, especially around the archipelagos of Indonesia and the Philippines (see map: "Coral Reefs of Southeast Asia"). These coral reefs provide a habitat for the highest biological diversity in the world (Wilkinson et al. 1993). Most shallow marine biota reach their peak diversity in these areas.
These reefs are under threat from anthropogenic pressures as a result of population growth, urbanization, and economic growth in the area. Reefs are being degraded and damaged by land and sea based human activities, including organic and inorganic pollution, sedimentation, and overfishing.
Policies and reserves exist to protect the reef; however, these are hard to enforce and monitor. Many illegal waste dumping and exploitative fishing practices continue to occur. As the region's populations, coastal cities, and economies continue to grow, the damage to coral reefs has become widespread. Research is urgently needed to assess the threat to Southeast Asian coral reefs and to develop strategies to prevent their destruction.
to Coral Reefs:
Southeast Asia is undergoing rapid economic and population growth. There are more than 440 million people in peninsular Southeast Asia alone, and the population is expected to double in 25-35 years (NOS 1998). Indonesia, with over 210 million people, is the fourth most populous country in the world. Indonesians are unevenly distributed across the archipelago, however. Over half the total population lives on one island, Java, an area of very high density. Throughout the region, the large majority of people live on or near the coast.
Many Southeast Asians are economically dependent on the sea and the coral reefs. About 60% of the region's animal protein comes from the sea. Fisheries extend from near shore to far off reefs (Wilkinson et al. 1993). Although there is little direct quantitative data on the effects of anthropogenic stresses, it is evident that the reefs of these region are being degraded and even destroyed. Some believe that it will take as little as 40 years for Southeast Asian reefs to be destroyed (Wilkinson et al. 1993).
The seas are being polluted by organic and inorganic wastes from sewage, from agricultural and industrial wastes, and from run-off containing oil, hydrocarbons, and heavy metals. All of these contribute to sediment run-off and increased turbidity. Siltation of coral regions is also caused by excessive deforestation and land clearing for commercial crops. Construction and land reclamation has caused changes in water circulation and has increased sedimentation. On the coral reefs, there has been extensive overexploitation of resources by heavy fishing pressure, including very destructive methods such as blasting, coral mining, and cyanide poisoning for live fish collection.
Industrial pollutants that affect coral reefs include nutrients from sewage and organic matter, fertilizer run-off, detergents containing phosphorus, and thermal discharge - the heated water from the cooling systems of power plants and other industries. These all cause nutrient overload, the growth of aquatic plant life, and the depletion of dissolved oxygen, or eutrophication. This retards coral growth by decreasing light penetration and changing the dynamics of fish assemblages. Other industrial pollutants include heavy metals and other toxic substances.
The coral reefs bordering major cities throughout Southeast Asia have been largely destroyed. Pollution from oil refineries and drilling platforms has been shown to kill reef fish and have negative effects on growth rates, recruitment, and feeding of corals. Thermal pollution from hot water discharge from industrial areas is an additional threat to reef species, as many of them cannot withstand sudden and drastic increases in temperature.
Land-based human activities often cause sedimentation, a major source of reef degradation. As more people move to coastal cities on the South China Sea, there has been a big increase in construction and land reclamation. Land reclamation and sedimentation has been particularly intensive in Singapore (see map: "Reclaimed Land in Singapore"). Land was reclaimed by dumping sand and dirt directly onto coral reef flats and shallow water (Hotta and Dutton, 1995).
These add to the erosion of beaches and sediment run-off that smothers the corals and leads to the degradation of the reef. Increased sedimentation also leads to a change in the composition of marine fauna, favoring more resilient species. Sedimentation also comes from soil erosion from unsound agricultural practices, mismanagement of watersheds, exploitation of mangroves, land reclamation and construction; oil drilling and the dumping of terrestrial and marine mine tailing.
Overfishing is an extremely destructive force to corals in the South China Sea. Densities of fish are greatly decreased by overfishing. Coral is damaged by destructive fishing techniques and by removal for trade. It is estimated that 10 to 15% of the total fish yield in the Philippines comes from coral reef fisheries (Russ and Alcala 1989).
Fishing degrades the reef in several ways. Destructive and illegal fishing methods are common, especially in the Philippines, Indonesia, and Malaysia. These methods include dynamite blasting and cyanide fishing. Overfishing not only depletes fish stocks of target species, but also changes the dynamics of the entire reef. Decreases in herbivores can lead to algal blooms which overtop coral growth and can cause mass mortality.
Huge amounts of oil pass through the waters of the South China Sea; all major shipping routes are polluted to some degree. Over 100,000 oil tankers and container and cargo vessels transit the Straits of Malacca and Singapore each year. These tankers carry over 3 millions barrels of crude oil through the straits each day (Tookey 1997).
Spills occur mostly by collisions or grounding. Ships deliberately dump oil wastes into the water. It is likely that they do this after cleaning the tanks to avoid having to pay to have them cleaned. Some areas can have more than 25 oil slicks in a 10,000 sq. km area at any given time. Oil slicks can be 100 km long and 3 km wide, double the length of Singapore. The smaller ones are still 100m by 100m. (see map: "Ocean oil pollution distribution")
Oil spills are causing major marine degradation in the South China Sea. In late 1992, an oil tanker collided with a container vessel in the Straits of Malacca, betweeen mainland Malaysia and Sumatra, and spilled 12,000 tons of crude oil (Tookey 1997). In January 1993, another tanker crashed into a ship off the northern coast of Sumatra and spilled 15,000 tons of oil into the Malacca Straits. These oil spills have seriously affected marine life and sea birds. They can also have a very negative effect of fisheries stocks and human health.
Maps and images:
Coral Reefs in Southeast Asia, in Coral Reefs and Mangroves of the World
The Coral Reef
Coral and Shell
Ocean oil pollution
Hotta, K. and Dutton, I.M. eds. (1995) Coastal Management in the Asia-Pacific Region: Issues and Approaches. Tokyo: Japan International Marine Science and Technology Federation.
National Oceanographic Institute (NOS) (1998) The State of the Reefs - ICRI's Major Concerns. http://www.nos.noaa.gov/icri/state.html
Oil Spill Intelligence
Reefs at Risk:
A Map-Based Indicator of Threats to the World's Coral Reefs. World Resources
Russ, G.R. and Alcala, A.C. (1989) Effects of intense fishing pressure on an assemblage of coral reef fishes. Marine Ecology Progress Series. 56:13-27.
"Ocean oil pollution distribution," Map from the National University of Singapore, Center for Remote Imaging, Sensing and Processing (CRISP), Singapore Straits Times, Nov. 26, 1998
Tookey, D.L. (1997) Shipborne pollution and the ASEAN co-operation plan on transboundary pollution. In: Oil and gas law taxation review. Oxford, England: ESC Publisher. pp.18-23.
Wilkinson, C.R., Chou, L.M., Gomez, E., Ridzwan, A.R., Soekarno, S., Sudara, S. (1993) Status of coral reefs in southeast Asia: Threats and responses. In: Global aspects of coral reefs: Health, hazards and history. Univ. Miami, Rosenthal School of Marine and Atmospheric Science. pp. J33-39.
Monitoring Center (WCMC) (1997) Marine Statistics for Southeast Asia.
This page was created and edited by Miranda Hillyard and David Rosenberg as a collaborative student-faculty winter-term project.
Last update: 5-20-00
Photographs: Mike Hurley, The Coral Reef Alliance, http://www.coral.org