South-east Asia

South-east Asia

As a parallel activity to the GESAMP global review, regional assessments were made. Gomez et al. (1990) prepared a report which covers the seas bordering the Association of South-East Asian Nations (ASEAN) and Hong Kong. The working group was composed of representatives of each country concerned. Another useful reference on the marine environment of the region appeared in 1988. The journal of the Royal Swedish Academy of Sciences, Ambio, published a special issue (Volume 17, Number 3) on the East Asian seas. An overview of the region's environmental problems (E. D. Gomez, 1988) was followed by articles on specific topics by different authors.

As mentioned above, the problems of the marine environment are more pronounced in marginal seas than in the open ocean. The seas of South-East Asia may be characterized as marginal. In the early 1990s, the Indonesian and Philippine archipelagos are inhabited by 250 million people, most of whom live in the coastal zone. The populations of the other ASEAN countries contribute another one-third of this number, in addition to those of the Indo-Chinese peninsula. The total population of South-East Asia in 1990 was placed at 440.8 million (WRI, 1990).

With population pressure exerting itself heavily in the coastal areas, there is great concern about habitat destruction. Among the most heavily affected are mangrove forests, the largest of which are in Indonesia. Big coastal areas in the more populous islands have been converted into fish and prawn ponds, with only the narrowest of mangrove strips remaining on the seaward side. Of about 2.5 million hectares of mangroves, some 700000 hectares were converted to various uses between 1969 and 1979. It is feared that an equivalent area will be destroyed before the end of the twentieth century. Malaysia ranks second in total mangrove area. Fortunately, of the more than 0.5 million hectares of mangrove coastline, perhaps less than 20 per cent have been converted to other land uses. The situation in the Philippines has been less positive. Of some 400000 hectares, only about 25 per cent remain. In the other countries, the position is not as bad. but all are threatened.

The coral reefs of South-East Asia are also under attack, although for a different reason. There is limited direct use of reefs except locally for mining lime. It is in the process of extracting fish and other marine products that the coral reef:s themselves are often negatively impacted. Illegal methods such as dynamite fishing have become widespread in the region. Overfishing of reefs has begun in many areas, whether it be for fish, invertebrates or seaweeds. A more serious threat in many regions, and particularly in the Philippines, is siltation resulting from the erosion of coastal areas due to deforestation and poor land-development practices. The Philippines provides one example of what can happen to coral reefs. E. D. Gomez (1989) presented a summary of their condition. Fully 70 per cent are in a poor-to-fair condition with less than 50 per cent live coral cover. The situation in the other countries is probably not much better.

The over-exploitation of fish stocks is becoming more evident. Any review of the fisheries of the region will show the drastic drop of stocks in the Gulf of Thailand in the 1960s. Later studies in the Philippines have revealed that demersal stocks and those of small pelagics have begun to decline. If long-term monitoring were undertaken, the trends could be documented in the various countries.

An equally severe problem, because of the sheer numbers of people in the coastal zone, is the organic pollution entering the sea. Most of this pollution is in the form of sewage, much of which is discharged untreated into rivers and coastal water bodies. To this is added the litter and other solid wastes that are so characteristic of areas near populated parts of the region, with the possible exception of Singapore. The amount of organic load in the coastal waters is becoming heavier. In some estuaries and embayments, eutrophication is increasingly evident as well as microbial contamination. More alarming, however, is the growing frequency of red tides, or paralytic shellfish poisoning in the region. The few occurrences in the mid-1970s became more frequent in the following decade; in the Philippines, eight cases were reported (Corrales and Gomez, 1990). The start of the 1990s is witnessing a further escalation of this trend.

In spite of the exploitation of oil and the large volume of oil shipping passing through the various straits of South-East Asia, pollution has not been out of proportion. The proceedings of a workshop held in Bali provides a review of the oil pollution in the region (Yap, de la Paz and McManus, 1988). Gomez et al. ( 1990) also contains a section on oil.

This review would not be complete without touching on mining activities affecting the marine environment. In addition to oil (2 million barrels per day) and gas (5 billion cubic feet per day), much of which is from offshore wells, there are tin-dredging operations that have caused problems in coastal areas, particularly in Thailand. In a few celebrated cases in the Philippines, the problem of disposing of copper-mine tailings into coastal waters has become prominent. Fortunately, these are not widespread.

Manila Bay

A few of the environmental problems of the Philippine marine waters and coastal ecosystems have already been mentioned in general terms. It would be well to illustrate on a finer scale some of the problems related to coastal waters adjacent to large population centres. For this purpose, Manila Bay can be used, as it may in some ways be compared with the Upper Gulf of Thailand, where the Chao Phraya River debouches after passing through Bangkok, and also with Jakarta Bay in northern Java.

Manila Bay is a semi-enclosed body of water comparable in size to the Upper Gulf of Thailand but with a narrow sill that connects it to the South China Sea. While several rivers empty into the bay, the two most prominent are the Pampanga River to the north, which drains a large agricultural region, and the Pasig River to the east, which, in addition to agricultural runoff, carries with it industrial and municipal effluents from the Metro Manila area. The more significant input of pollutants into the bay comes from the large metropolis, whose population is now in the order of eight million. Only a small fraction of the households in the greater Manila area are sewered.

Studies on marine pollution in the Philippines were reviewed by Deocadiz ( 1990), who indicated that Manila Bay is contaminated with pesticides, industrial wastes and oil, in addition to domestic wastes. While earlier studies tended to show rather high values of heavy metals, which may have been artefacts of the analytical methods used, later studies (for example, Soria and Theede, 1990) indicate only a mild contamination of Manila Bay by heavy metals. In sharp contrast, Acorda ( 1990) indicated that bacteriological pollution has been on the increase, to the extent that the waters of eastern Manila Bay have been declared unsafe for bathing. This bacteriological pollution is no doubt due to the high input of raw sewage into the bay. It is suspected that the organic pollution in the bay has contributed to the increasing frequency of red tides as mentioned earlier.