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Factors promoting the spread of fire
Matthews (1989) has suggested that the danger of wildfire arises from a combination of fire risk and fire hazard. Risk increases when there are people, roads and railways in or passing through the forest, as well as fire in the adjoining land. Hazard, on the other hand, increases when there are large amounts of flammable dry vegetation or slash in the forest, and these conditions are associated with high wind speed, low relative humidity and high air temperature. The danger of wildfire becomes extreme when high risk is combined with high hazard.
The potential for fire to spread, according to Bormann and Likens (1979), is determined by factors such as patterns of wind flow, distribution of water bodies (lakes, stream and wetlands), topography and dryness of soil (due to texture, soil depth, slope and aspect), as well as composition, accumulation and spatial distribution of organic fuel on the ground. With reference to organic fuel, susceptibility to fire and its spread may be greatly reduced in the humid Tropics, where effective decomposition by bacterial, fungal and detritivore activities can contribute to a rapid turnover of litter, and to only modest standing crops of dead wood and forest-floor material. Indeed, it was stated by Paul W. Richards (1952), Whitmore (1984) and Mueller-Dombois (1981) that fire cannot burn pristine tropical rain forest.
However, these elements in a potential fire condition can be combined in a number of different ways. Prior to the great forest fires in Sabah and East Kalimantan in 1982-3, and perhaps also in other tropical rain forest areas, the conditions involved the interaction of at least five major factors. These were swidden agriculture, logging activities, specific properties of the substrates, flammability of the biomass and change of climate (Leighton and Wirawan, 1986; Wirawan, 1985).
The origin of the 1982-3 fire has not been definitely identified, but swidden agriculture has been considered as one of the most plausible sources (Wirawan, 1985). Swidden, slash-and-burn or shifting agriculture has been traditionally practiced by rural people in Borneo, as in many other parts of the Tropics. With the intention of planting crops at the onset of the rainy season in November or December, they usually start clearing and then burning their fields during the second half of the dry or less rainy period, usually in September and October. The timing of this slash-and-burn practice is well-established and is primarily based on the annual variation of the monsoon. While November or December rains will provide a final check on the spread of fire, people usually select and clear their fields in isolated places, so that wildfire cannot spread beyond them. The extensive logging activities during the 1970s and 1980s, however, have brought about changes in this traditional practice.
Logging activities have greatly increased both fire risk and hazard (C. Mackie, 1984). Access roads opened up the forest to both immigrant and local people for making fields. While shifting agriculture has been considered the major cause of the deforestation in South-East Asia, a study by FAO/UNEP (1981) showed that 70-80 per cent of swidden cultivation took place in recently logged-over forest areas. As agriculture was mostly developed along or near the logging roads, rather than isolated within the forest, the sources of fire were brought closer to each other and into the forest itself.
By opening up the forest canopy, logging activities have greatly stimulated the growth and accumulation of plant biomass near the ground. Additional dead biomass is also provided by deformed logs and branches left behind by loggers. A study by Phillips (1986) in Sabah found that 55 per cent of the 120 cubic metres per hectare of wood felled was left behind to dry and rot on the forest floor. The failure of the rainy season to arrive on time, as was the case in late 1982, prolonged the dry season, dried this plant biomass, and then helped the fires started by shifting cultivators in September or October to spread wildly unchecked for several months until heavy rains fell in May 1983. As a result, 85 per cent of the burned forest in Sabah, and 70 per cent in East Kalimaritan, occurred in the logged-over forest areas.
As already discussed, forest damage varies with logging intensities. Forests in many isolated hills or unlogged areas were not burned, and fire did not penetrate beyond 2 kilometres into the undisturbed forest from the boundary of the burned logged-over area. Even there, only the thin litter layer and trees smaller than 5-10 centimetres in diameter were destroyed (Wirawan, 1984b). The areas most severely affected by the fire were those located along the access roads, where logging was most intense (Kompas, 1984a; Wirawan, 1985). Table 11.1 shows that only I I per cent of the 410000 hectares of undisturbed primary forest was affected-lightly-by the fire. In contrast, the area burned increased to 58 per cent in the lightly disturbed or logged forest, to 84 per cent in the moderately disturbed forest, and to 88 per cent in the heavily logged forest.
Properties of Substrates
The specific properties of substrates that can promote the spread of fire are related to dryness, which helps make the available biomass more combustible. Because of differences in soil-water retention (due to texture, depth, organic-matter content and other qualities), during a rainless period, one substrate may be drier than others. Examples of extreme substrates are ultramafic soils which often occur on steep hillsides (Beaman et al., 1985), as well as soils on limestone, siliceous sand deposits (podzols) and, under extreme conditions, also peat. While in the fine-textured soils, up to 70 per cent of the dominant Shorea and Dryobalanops- canopy trees larger than 60 centimetres in diameter were killed by the long drought in the Kutai National Park (Wirawan, 1984a), the complete burning of segments of the limestone forest (56 per cent), heath or kerangas forest (45 per cent) and peat forest (72 per cent) was probably preceded by the drying of these forests.
Although peat forest has not been considered inflammable (Mueller-Dombois, 1981), under extreme conditions as in 1982-3, the water level in the rivers surrounding the peat swamp in the middle Mahakam area was 6 metres below normal; much of the surface layer may already have been dry before fire began. Since most of the rooting systems are in this upper layer. many of the trees may already have died. The dried trees and peat in the substrates provided extra combustion energy for the subsequent fires to burn the forest more intensively and extensively (Malingreau, Stevens and Fellows, 1985).
Certain substrates may also facilitate the spread of fire even below the ground surface. The author observed in the transmigration area at Padang Sugihan near Palembang, South Sumatra in late 1982 that one may walk on the peat surface while smoke from the burning peat beneath obstructs one's vision. In East Kalimantan, fire was also spread by the exposed coal seams that occur in a series of bands within an area of about 20 kilometres from the coast. In fact, some of these exposed coal seams that caught fire in 1982-3 are still burning.
Flammability of Biomass
The relatively thick layer of litter that accumulates during a long drought period can easily fuel a surface fire, but such fire is generally of low intensity and does not produce significant flame. This starts when the fire burns logs and branches Iying on the ground, or the standing dried shrub layer, before reaching the tree canopy. The burning of the standing trees, however, is quite variable, depending on species composition and stand density. In Borneo, the lowland forest is dominated by members of the dipterocarp family. All Bornean members of this family as well as certain members of the Burseraceae, Guttiferae, Anacardiaceae and Styracaceae families produce resin or damar from their trunks (Gianno, 1986; Meijer and Wood, 1964). Except for the species of the genera Dipterocarpus and Anisoptera which produce liquid resin, all other species have resins that harden soon after exudation.
The damar resin is a fuel and has commercial value. Liquid resin is collected by firing after tapping (Ashton, 1982; Gianno, 1986). The hard resin, however, is gathered either by felling the tree and then collecting the crystals by splitting the bole (for camphor of Dryobalanops aromatica) (Ashton, 1982) or tapping the bole; or digging the soil at the base of the trunk. While the amount produced may vary with the species, 200 500 litres of oleoresin may be tapped from 200 to 250 trees by I person in I week, and 5-6 gunny sacks may be collected from the base of a single Shorea longisperma tree (Gianno, 1986).
These damar are highly flammable. When lit, they burn continuously and the native people use them for torches or lighting (Gianno, 1986). In fieldwork, damar is usually used as a fire starter. Since it does not absorb water, it is not affected by rain. Because of this property, the dipterocarps and all other damar-producing trees are normally quite susceptible to fire. Moreover, as canopy trees of certain species were already killed and dried by prolonged drought, the damar-producing dipterocarps would have been highly combustible. The 'wide scattering towering infernos as the tops of drought-stricken, formerly evergreen trees sent jets of flame more than 60 meters above the forest floor' and the huge explosions that produce fireballs resembling 'shell bursts in the smoke', as observed and described by a German expert (Dr Wolfgang Weisner) working in the province (Asiaweek, 13 July 1984), could have originated from the accumulation of those damar or damar-producing trees.
As the distribution of such species ranges from solitary, to clumps of a group of individuals, to stands that occupy relatively large areas such as a ridge or a slope, the burning of these tree species could be another reason for the variability of forest damage. Such variation is also related to the survival of trees that are somewhat resistant to fire. Some of these trees are Borassodendron borneensis, Eusideroxylon zwageri, Koordersiodendron pinnatum, Alstonia sp. and Dyera sp. (Leighton and Wirawan, 1986; Tagawa et al., 1988; Wirawan, 1985).
As discussed in some detail by Nicholls (Chapter 7) the extended drought that delayed the start of the rainy season in 1982 was associated with a very strong El Niņo Southern Oscillation (ENSO) event. Since El Niņo is associated with a dry or drought period in much of South-East Asia, an accurate prediction is vital for improved preparation to avoid the serious effects of drought and large-scale fire, elaborated above. This is of particular importance in a region, such as eastern Borneo, which has sufficient rainfall in most years to support the tropical rain forest, and where it is almost only during El Niņo events that wildfire occurs.
Outlook for Fire Incidence
In principle, all five factors discussed above will continue to exist into the future. Logging will remain part of economic activities, and swidden agriculture will be practiced for the foreseeable future. Little can be done to change the specific properties of the substrates and the flammability of plant biomass in order to reduce their susceptibility to fire. Although there are certain plant species that are more resistant to fire and these must be used increasingly, the majority of the necessary and desired timber species-such as the dipterocarps-are very susceptible to fire, if not highly combustible. Furthermore, while the cyclic variation of climate is highly irregular, there must be improved understanding and prediction of such change.
While each of the elements contribute to the risk, hazard and spread of fire, it is the timing of the burning of swidden fields in relation to the start of the rainy season that seems to be most critical. Long-term experience and adjustment to the relatively regular wet and dry annual climatic cycle determine the right time to burn the swidden field. The rains of the wet monsoon normally provide water to the young crops, as well as help stop the spread of fire. The burning, therefore, is done at a specific period of the year. In contrast, the cycle of ENSO events is quite variable. It severely affects the welfare and economy of the people and the country, and the reduction of its impacts would greatly benefit the local people and government. To meet these aims, and based on the discussion of the factors that promote the spread of fire, special attention should be directed at swidden agriculture and logging or timber-production activities.
Reducing the incidence of large-scale fire
In discussing the means by which the incidence of forest fires can be reduced, Matthews (1989) suggested three major steps. The first step is the establishment of an organization for speedy reporting, while the second is the provision of effective means for suppressing fires, and the third is the prevention and control of fires. Soon after the 1982-3 fire in East Kalimantan, the Indonesian government took actions related to the first and second of these steps. However, in spite of the devastating loss of biological resources (particularly timber) and the continuing potential of fire risks and hazards, it appears that no special measure for preventing and controlling forest fire has yet been included in the logging procedures in Indonesia. The 1991 fires, during which appeals were made for international help to fight the conflagrations, might now spur action.
Soon after the 1982-3 fire, pilots were required to look for and report on the occurrence of any fire observed during regular flights over the area. These actions should be continued. To help pilots make accurate reports on the location of fires, it would be useful to provide maps of the area on which to mark sightings. This could then be handed to the airport authority at the end of the day and all pilot reports over a period of time could be compiled into a single map. This map should be available to the general public, and those charged with the suppression of fires should regularly receive a copy of the map. The principal airport meteorological stations could be charged with keeping such a map and co-ordinating its distribution.
In case of fire, the military and the forest agency (Kanwil Kehutanan) are perhaps the best equipped to co-ordinate and carry out suppression. While the military has a large reserve of organized manpower that can be sent to the sites of fire at relatively short notice, the Kanwil Kehutanan could organize the local logging companies to provide the necessary logistical support.
Because the suppression of large-scale wildfire will always be difficult, prevention or control of its spread is the best measure. Critical factors to consider include swidden fields as potential sources of fire, logging activities which promote the growth or accumulation of combustible biomass near the ground, and the severe fire damage that has occurred along logging roads and in heavily logged areas. Moreover, logging roads are usually located on ridges that are relatively dry and more susceptible to fire than other locations. Many canopy trees, mostly dipterocarps (Shorea and Dryobalanops), were killed by the drought and, in general, fire would not extensively burn the undisturbed primary rain forest. Despite this factor, the dominant presence of dipterocarps and other damar - producing trees could make the South-East Asian rain forests highly susceptible to fire, if not even highly combustible in the presence of unusually dry conditions.
Based on these considerations, measures could be taken for reducing the incidence of fire. Perhaps potentially most important are communitydevelopment programmes for forest dwellers or those living in villages adjacent to forest areas. These matters need to be handled with care because of the resistance of shifting cultivators to externally induced programmes of change (Atal, 1984). Direct involvement of rural communities in planning, implementation and development of programmes leads to a better chance of success (Chambers, 1984; de los Reyes, 1984).
Buffer zones that economically benefit these communities should be promoted. They could be established by helping communities develop agroforestry techniques that serve their needs as well as meet the criteria for reducing fire threat. Through correct selection of species and planting designs that are to be applied along the forest boundaries, these fields could become an effective firebreak. Many ethnic groups are well known for their capabilities in developing traditional forestry practices and, in establishing such a buffer zone, it is very important to first investigate the local traditional methods as the basis for development (Wirawan, 1990).
No less important are better forestry practices, including the establishment of effective firebreaks along logging roads. These belts of trees should preferably be resistant to fire. They should be planted in alternating stands of different species and ages in burned forest along logging roads so that future logging of these trees would not be carried out at the same time. This plan would avoid forming a uniform corridor that may become an effective way of channelling the spread of the fire. Controlled burning of the forest litter layer is important along these firebreaks, especially during an expected El Niņo year.
Logging blocks should be established in a mosaic pattern and cut in different years so that the remaining stands consist of forest of different ages and structure. In developing industrial tree plantations of the highly flammable damar-producing dipterocarps, these trees should be mixed with fire-resistant economic species, such as the ironwood or ulin (Eusideroxylon zwageri) and the sugar-producing aren-palm (Arenga pinnata). Plantings of dipterocarp and other high-risk trees in monocultures should be avoided. Other fire-resistant timbers and non-timber economic species should be identified in order to support the development of fire-safe timber plantations. Only by measures such as these can the greater holocaust of the next major El Niņo be avoided.
A wider view of the fire hazard
WIRAWAN has comprehensively reviewed the fire hazard in the Tropics with special reference to South-East Asia, including the occurrence of the big fire in the lowland tropical forest of East Kalimantan in 1983. The following remarks will provide additional information on fire relations in natural tropical ecosystems in South-East Asia.
The fire of 1983 in East Kalimantan and Sabah took place in a tropical rain forest on well-drained soils. A small-scale study of a permanent plot in East Kalimantan by Riswan and Yusuf (1986) found that the rate of death of trees in primary forest was about 20 per cent while in the 40-year-old secondary forest it was about 32 per cent. Many surviving burned trees were able to coppice, that is, 32.5 per cent in the primary forest and 35.5 per cent in the secondary forest. Many other species were not affected by the fire.
There are also several important intra-zonal ecosystems in the South-East Asian Tropics in which the controlling factor is an extreme soil variation (Mueller-Dombois, 1981). These include the kerangas (heath) forest on podsolized soils over white sands, forests on limestone and ultrabasic soils, and peat-swamp forest. Fire has been recognized as a natural factor in these edaphically extreme rain forest ecosystems (Bruenig, 1974; Kartawinata, 1978; Mueller-Dombois, 1981; Whitmore, 1984). In these ecosystems, the activities of micro-organisms are impeded, leading to the accumulation of raw humus and litter, which in turn provides enough fuel for fire to burn during the unusually prolonged dry season. The author recorded, for instance, a deposit of charcoal at a depth of I metre in the soil of a kerangas forest surrounded by a vast extent of primary lowland dipterocarp rain forest in East Kalimantan, indicating the occurrence of (perhaps natural) fire in the past (, 1980). Endert (1927) reported the periodic occurrence of fire in the peatswamp forest following an unusually long drought in East Kalimantan, leading to the formation of the tall grass swamp community.
Fire recurs regularly in another zonal ecosystem-the monsoon-forest ecosystem which includes the evergreen and semi-deciduous forests. Its distribution extends from Myanmar to Thailand, Vietnam, the Philippines (northem Luzon), Indonesia (South and South-east Sulawesi, East Java, East and West Nusa Tenggara, East Timor and South-east Irian Jaya) and Papua New Guinea (South-west), coinciding with the monsoon climate where the drought period is usually long (Paul W. Richards, 1952; van Steenis, 1935, 1957). Fire occurs regularly, if not annually, and in many cases it has led to the formation of various types of savannah and grasslands. In Irian Jaya and Papua New Guinea, for instance, it occurs in the dry evergreen forest and has resulted in the formation of various types of savannah (for example, Melaleuca-Tristania-lmperata, Melaleuca-Themeda australis, Tristamia-Grevillea-Banksia), woodlands, fern scrubs and several types of grasslands (for example, Sacchurum-Imperata, IschaemumThemeda, Schoenus-Eriachne), as well as pure casuarina forest extending from lowland forest to lower montane forest zones (Paijmans, 1976). Similarly, in East Nusa Tenggara, regularly recurring fire, in combination with grazing, has changed dry evergreen Eucalyptus forest to Eucalyptus-Heterapogon savannah and HeteropogonThemeda-lmperata grasslands, as well as dry evergreen mixed forests to Acacia or Borassus-Corypha palm savannah and various grasslands (van Steenis, 1935). Fireadapted woody plants are particularly common in these ecosystems.
Altitudinally, fire follows the occurrence of the most combustible plant life forms and thus vegetation. In the montane environment, various ecosystems accumulate a certain amount of humus. For this reason, Mueller-Dombois (1981) concluded that montane forests are more prone to surface fires than tropical lowland forests. Paijmans (1976) indicated that in Papua New Guinea (and perhaps in Irian Jaya also), extensive high mountain grasslands and savannahs below the timber line are secondary in nature and of anthropogenic origin. High montane forests, swamp forests, sedge-grass swamps and grasslands experience dry periods and fire can set in, usually starting from the swamp grasslands and then spreading to the other ecosystems. Fire occurs every year but less regularly than in the lowlands (Paijmans, 1976). Because of different habitat conditions and, thus, different species composition with different degrees of combustibility, fire occurrence is usually patchy and has resulted in the formation of a mosaic of successional and subclimax vegetation. Van Steenis (1935, 1972) indicated that the occurrence of the pure Casuarina junghuhniana forest in the mountains of East Java is maintained by recurrent burning; this tree species is fire-resistant.
The spatial and temporal variations and impacts of fire in an ecosystem can be more properly assessed if information on site characteristics as well as existing and potential vegetation is established, because the variable effects of fire make any prediction difficult (Daubenmire, 1968). This is particularly important for a rational approach to land management in the tropical countries where data on ecologically based inventories of lands and vegetation are scarce (Mueller-Dombois, 1981).
Few observations on forest succession following a fire are available for tropical rain forests and particularly seasonal forest areas. When the area is relatively small and does not experience recurrent burning, re-establishment of the forest can take place, but if the area is large and especially when accompanied by recurrent burning, conversion into savannahs or grasslands results. This is usually accompanied by site degradation, such as a decrease in fertility and deterioration of physical properties of the soils. Floristic diversity is dramatically changed and its recovery is extremely slow, even in the most favourable environment of a tropical rain forest.
Small-scale experiments in a lowland dipterocarp forest and a kerangas forest show the trend of early succession in burned and unburned sites in the above forest types (Riswan and Kartawinata, 1988b, 1989, 1991). In the kerangas forest on podsolized white sand soil (Riswan and Kartawinata, 1988b), it was observed that after 1.5 years (78 weeks) in burned and unburned plots, coppicing from the burned vegetation was the main feature of the vegetation recovery, while regeneration through seedlings played an insignificant role (Figure 11.3). Species composition in both sites was very similar and this was attributed to coppicing of the original burned woody forest species. Poor development of seedlings was due to very acidic and low nutrient content of the soil. Seedlings may have developed from seed banks in the unburned site and seed-rain in the burned one.
Fire does not seem to be the determinant of the direction and the rate of the secondaryforest succession. Clear cutting followed by burning had more destructive effects than clear cutting without burning, as indicated by the fact that, after 1.5 years, 10 per cent of the burned site was still bare compared to only 2 per cent in the unburned site. The addition of nutrients in the form of ash from the burning of felled vegetation did not seem to accelerate the recolonization by seedlings or the growth rate of coppices (Riswan, 1982). Whether the disturbance was clear cutting or clear cutting followed by burning, the effects on species composition, overall growth and cover of vegetation were not substantially different. Perhaps changes occurring in the successional patterns may be attributed to the differing strategies of individual species in the two conditions. The effect of clear cutting, with or without burning, is not only to destroy the overall nutrient cycling of the complex soil-plant ecosystem but also to wash out most of the nutrient elements (stored in the forest system) through erosion and leaching processes, which are accelerated by poor vegetation recovery (Riswan, 1982).
FIGURE 11.3 Number of Species of Seedlings and Resprouts in the Experimental Burned and Unburned Plots in a Primary Kerangas Forest at Samboja, East Kalimantan
In the dipterocarp forest on red-yellow podsolic soil in the early stage of succession, seedlings played a more important role than coppices (Figure 11.4) (Riswan and Kartawinta, 1989, 1991). The number of species, percentage of cover, frequency of seedlings and coppices, and the number of primary forest species were greater in the unburned than in the burned site. The dominant species in each site differed, even though they were adjacent. The recovery in the unburned site is thought to be attributable mainly to the undisturbed seed bank in the soil, as indicated by the high number of primary forest species developed. The recovery process of soils in the burned plot was faster than that in the unburned one. In general, however, they show very fast recovery after a disturbance (Riswan, 1982).
FIGURE 11.4 Number of Species in the Experimental Plots MDF Samarinda, East Kalimantan
Later succession, 35 years after burning and abandonment of a pepper plantation, shows that floristically 70 per cent of the species were primary forest types of which only one was a dipterocarp, although the site was surrounded by primary dipterocarp forest (Riswan and Kartawinata, 1988a). By using a floristic similarity index, the stem biomass and girth measurement, it was estimated that it would take 150-500 years for the site to return to conditions similar to the original forest (Riswan, Kentworthy and Kartawinata, 1985; Riswan and Kartawinata, 1988a).
FIGURE 11.5 Changes in Number of Species of Plants and Insects after Yearly Clear Cutting and Burning
Early succession was deflected when fire took place more frequently. Repeated burning at 6-monthly intervals converted the clear-cut, lowland dipterocarp forest into an Imperata grassland within 3 years (Kartawinata et al., 1983). During that period, the species diversity decreased drastically from 201 species of flowering plants per hectare in the 6-month-old successional community in the clear-cut forest without burning, to only 23 species in the grassland (Figure 11 .5).
Mueller-Dombois ( 1981 ) stated that fire frequency and intensity are fundamental factors, whether the effects of fires are negative or positive. In view of the fact that every region has its own peculiarities, the role of fire varies between regions and between habitats within the same region. In the temperate and subtropical regions, a great deal of knowledge on fire management is available, but successful firemanagement practices should not be extrapolated to the Tropics without modification. In this respect, he further stressed that there is little useful application of fire in tropical forests.
The need for management
A review of fires in South-East Asia needs to look beyond Kalimantan and Sabah. The pine forests in the Philippines may be maintained by fire. The idea of fire as a major factor in forest ecology is new, having taken hold only since 1983; formerly we believed that the rain forest would not burn, even though there was evidence of fires and of the smog that they produced, from Sumatra in particular. The question of prevention measures is important. In Indonesia, the State Ministry of Population and Environment has formed a committee to study measures of prevention and control. As of the early 1990s, there is no provision for fire control in the Indonesian Selective Felling System, nor for that matter in either the Philippine or Malaysian systems. There are, however, some guidelines for the control of fire in plantation forests, and some watchtowers have been erected in mangrove forests.
In the reforestation of Imperata cylindrica grassland, Indonesia has applied the socalled block-corridor system, where the blocks are the plantation sites and the corridors are the firebreaks of fire-resistant species, such as the Macadamia hildebrandii in Sumatra; the corridors are at least 20 metres wide. A community-development programme is a good idea, as also is that of firebreaks along logging roads; however, it is doubtful whether controlled burning along such breaks would be feasible. Wirawan's suggestions are in agreement with present ideas and practices in Indonesian forestry.
In discussion, it was suggested that the heat from extensive forest fires in South-East Asia might intensity the El Niņo-Southern Oscillation (ENSO) circulation. Nicholls responded that, large though the heat output is, it can have only a minute positive feedback effect on a phenomenon of global scale. The energy involved in ENSO is very many times that released in Asian or any other forest fires. However, it can be predicted that events of the 1982-3 order might occur about once a century, with events close to that magnitude occurring four or five times during a century. Therefore, if human activity continues to intensify, the next major fire event will be much worse.
12. Coastal, inshore and marine problems
EDGARDO D. GOMEZ
As in most books dealing with the environment in general, this one also tends to show a bias towards the terrestrial environment. However, it is fortunate that some attention is being given to the marine environment; the marine areas of South-East Asia more than equal those of the land. This region, which is the isthmus between the Pacific and Indian Oceans, is unique in the world for having two large archipelagic states (Indonesia and the Philippines), which between them account for some 20,000 islands (Figure 12.1). But whether we are concerned with these 'multi-island' states, or the more continental countries like Malaysia and Thailand, the greater bulk of the region's people inhabit the coastal zone. Large populations on the coast necessarily have great impact on the sea, hence, the title of this chapter. There will be no attempt to differentiate between the terms 'coastal', 'inshore' and 'marine'. Since South-East Asian seas are generally referred to as marginal seas, the marine environment of the region as a whole will be the subject matter of this chapter.
Ever since Goldberg (1976) wrote his book, The Health of the Oceans, interest in the monitoring of the global marine environment has become more acute. The Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP), an interagency body sponsored by eight United Nations organizations (IMO, FAO, UNESCO, WMO, WHO, IAEA, UN and UNEP), has been entrusted with a periodic review of the condition of the oceans. Its most recent report is The State of the Marine Environment (GESAMP, 19913. The author was a member of the working group that prepared the report and will attempt to abstract the more important observations in introducing and placing in perspective the marine environmental problems of South-East Asia.
The report points out that man's 'fingerprint' is found everywhere in the oceans but that conditions vary widely. In contrast to statements (by some crusaders out to save the oceans) that the oceans are dying, the report indicates that the open seas are relatively clean, although chemical contaminants are detectable virtually everywhere and sea lanes are often characterized by oil slicks and litter.
FIGURE 12.1 The Regional Seas
The picture changes at the margins of the sea because it is here that the impacts of man's activities are most pronounced. Besides the in situ population growth in coastal areas, migration from the interior to the coast continues in many places; hence, there is increasing pressure to develop coastal human settlements which necessarily leads to the destruction of natural ecosystems including beaches, wetlands and coral reefs. The next most important factor is the impact of nutrients and sewage on the coastal zone, whether these are generated locally or transported from interior watersheds,
On a positive note, there appears to be a decreasing trend in the contamination of some northern temperate areas by chlorinated hydrocarbons due to stricter controls of their use. Unfortunately. the same cannot be said for tropical and subtropical areas.
To sum up the report, it is best to quote its conclusions thus:
[A]t the end of the 1980s. the major causes of immediate concern in the marine environment on a global basis are coastal development and the attendant destruction of habitats, eutrophication, microbial contamination of seafood and beaches, fouling of the seas by plastic litter, progressive build-up of' chlorinated hydrocarbons, especially in the tropics and the subtropics, and accumulation of tar on beaches. However, concerns may differ from region to region, reflecting local situations and priorities. Furthermore, throughout the world, public perception may still accord greater importance to other contaminants such as radionuclides, trace elements and oil. These were highlighted in the 1982 GESAMP Review and are considered again in the present report, but we now regard them as being of lesser concern.
While no areas of the ocean and none of its principal resources appear to be irrevocably damaged, and most are still unpolluted, while there are encouraging signs that in some areas marine contamination is decreasing, we are concerned that too little is being done to correct or anticipate situations that call for action. that not enough consideration is being given to the consequences for the oceans of coastal development, and that activities on land continue with little regard to their effects in coastal waters. We fear. especially in view of the continuing growth of human populations, that the marine environment could deteriorate significantly in the next decade unless strong, co-ordinated national and international action is taken now. At the national level in particular, the concerted application of measures to reduce wastes and to conserve raw materials will be essential. The efforts will be great and costs high, but nothing less will ensure the continued health of the sea and the maintenance of its resources.
The report is not entirely silent on the current 'buzz' words in ecology or environmental protection. It takes cognizance of global climatic change, the possible sea-level rise that may result from global warming due to increases in greenhouse gases, and the potential impact of the reduction of stratospheric Ozone. Since these could not be fully assessed by the working group charged with the preparation of the report, they were not addressed in any detail but merely flagged as additional issues that will need further treatment elsewhere.
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.
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.
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