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1. Socio-economic and demographic aspects of mangrove settlements

Peter Kunstadter

Introduction

This paper reviews some of the progress made over the past 15 years in studies of socioeconomic and demographic aspects of human use of mangrove areas, with emphasis on South-East Asia. Mangroves are usually defined in terms of the distribution of characteristic tree species. Mangrove forests are found growing in brackish water on the margin between land and sea in tropical and subtropical areas, but, as with other definitions of ecological zones, this is not completely satisfactory because the exchange of individual organisms, nutrients, and energy between this margin and both the sea and upstream areas is at least as important as what goes on within the geographic limits of mangrove tree species (fig. 1).

Discussions of the socio-economic aspects of human settlements in the mangroves are difficult for several reasons. Mangrove forest ecosystems and the socio-economic systems of mangrove settlers are not coterminous, and, as compared with the natural ecosystem, information on the socioeconomic systems of mangrove dwellers is sparse. Most of it deals with economics (e.g. yields of forestry and fisheries), and relatively little describes the social and human ecological systems of the human residents.

Long-term residents of mangrove areas are generally similar ethnically to the inland populations (see, e.g., Aksornkoae et al. 1984, 34ff.), but their way of life often involves adaptation to mangrove environmental conditions, and economic exploitation of several distinct ecological zones. Thus mangrove dwellers have many different socioeconomic systems, some of which are primarily focused on subsistence activities (including both agriculture and fishing! and some are primarily commercial [including agriculture, fishing, and forestry).

Traditional mangrove dwellers often combine the use of land, sea, and inter-tidal resources. Even with limited economic development and modenization, the boundaries of the social and economic systems that influence mangroves spread well beyond the ecological limits of the zone itself. For example, charcoal from mangroves has long been an item of international trade, as have fish and shellfish. With increasing economic development, the boundaries of the socio-economic systems that use mangrove resources spread even further. The future fate of the mangroves (e.g. with respect to extractive forest harvest or the hazards of pollution from oil transported by sea, or the spread of industrial development to and along the coastline, or the development of seaside resorts or condominiums) may be decided in the air-conditioned board rooms of temperate-zone businesses. Thus the proper study of the socio-economics of mangroves must include some attention to national and even international social, economic, and demographic processes (fig. 2).

Although rich in many resources, mangrove forests have traditionally been sparsely settled and unintensively exploited by humans. In South-East Asia this has probably been the result of the scarcity of fresh water for domestic use and the unsuitability of mangrove soils for long-term agricultural exploitation; in Papua New Guinea it may have been the consequence of the presence of highly effective mosquito vectors of malaria. Modernization (e.g. development of motorized transportation or the extension of modern urban water supplies) has allowed the spread of human populations into mangrove areas without requiring that the newcomers adapt to mangrove ecological conditions. At the same time, modern technology has made the clearing of mangroves and their conversion to other uses such as shrimp ponds or urban dwelling sites relatively inexpensive, thereby opening mangrove areas for more intensive exploitation, with rapid environmental change and rapid expansion of the human population.

Because forests are one of the major mangrove resources, studies of mangroves have often been conducted as forestry research. Fifteen years ago the emphasis in studies of all aspects of forestry was on the upland forests, while mangroves were "the forgotten forests." Following the massive destruction of mangroves associated with the military use of herbicides in Viet Nam, and the attention focused on those forests by the American Association for the Advancement of Science and the National Academy of Sciences (e.g. Committee on the Effects of Herbicides in Vietnam 1974, sec. IV C), scientists from Thailand were drawn into studies of their own, relatively well preserved mangroves. Largely as a result of the efforts of Sabhasri 11979) end Aksornkoae (e.g. Aksornkoae et al. 1984), mangrove forests in Thailand are now among the best studied and best known in the world. As attention was being drawn to mangrove forests, the importance of mangrove fisheries and spawning grounds was also being recognized (see, e.g., MacNae 1974; Martosubro to and Naamin 1977).

FIG.1. Characteristics of mangrove management systems: traditional subsistence economies

Several ecological and economic characteristics of mangroves are now relatively well understood:

- Mangrove forests perform multiple ecological functions (e.g. production of woody trees; provision of habitat, food, and spawning grounds for fish and shellfish; provision of habitat for birds and other valuable fauna; protection of coastlines and accretion of sediment to form new land), and some of these functions have benefits far beyond the geographical limits of the mangrove zone itself (Hamilton and Snedaker 1984; MacNae 1974; Saenger, Hegerl, and Davie 1983).
- Mangrove areas have high biological productivity associated with heavy leaf production and leaf fall, and rapid decomposition of the detritus (see, e.g., Christensen 1978; Knox and Miyabara 1984, app. 1).
- The mangrove ecosystem is dynamic, changing in both location and composition, and has great resilience with the ability to restore itself after heavy damage, as long as seed sources and water flow are maintained (Committee on the Effects of Herbicides in Vietnam 1984; Lai and Feng 1984). There are many direct economic benefits from mangrove resources (mangroves may be, e.g., a source of firewood and charcoal, self-renewing sites for collecting fish and shellfish, sites for collecting honey, an attraction for tourism) (Hamilton and Snedaker 1984, chs. 3, 5, 6, 9). In comparison with irrigated farms and upland forests, the relatively undisturbed mangrove forests in South-East Asia provide a salubrious environment for people, associated with the absence of vectors for important diseases (Kunstadter, in press). In the relatively undisturbed state, mangrove forests do not support the reproduction of the local brackish-water malarial mosquito Anopheles sundaicus (Arwati 1977; Boschi 1975, 1976; Desowitz et al. 1974). This is in contrast with New Guinea, where highly effective malaria vectors IA. farautí) breed in undisturbed mangrove areas (Smithurst 1970; Spencer 1964, 1976), so that malaria inhibits human settlement in these zones (Petr 1977).
- Mangrove zones are useful for a great variety of human settlements, ranging from villages for near-subsistence fisherfolk to housing and industrial developments (Hamilton and Snedaker 1984, ch. 10).

FIG. 2. Characteristics of mangrove management systems: modern market economies

Despite their natural resilience, mangroves are threatened on a worldwide scale with unprecedented widespread and long-term damage or destruction. The harmful consequences of human activities upstream (e.g. due to various forms of agricultural and industrial pollution) and downstream (e.g. due to oil spills) are now widely recognized (Lai and Feng 1984; Chia and Charles 1984; Gomez 1980; Piyakarnchana 1980; Saenger, Hegerl, and Davie 1983, ch. 5; Soegiarto 1980; Zoology Department 1980). The most serious threats, however, seem not to be the indirect effects of human activities but rather the more direct consequences of human efforts aimed at rapid commercial exploitation of raw materials from the mangroves (e.g. for cellulose as in Kalimantan and Papua New Guinea) or converting the ecosystem to some use which is not compatible with regeneration of the forest, as in land "reclamation" for agriculture, aquaculture, housing, or industry (Kunstadter and Tiwari 1977, 3; Sabhasri 1979, 5, 14ff.).

Mangrove forests now appear to be affected by the same processes associated with modernization and economic development that have led to the rapid loss of other types of forest in Thailand and elsewhere in the tropics (Kunstadter, Chapman, and Sabhasri, in press). These include rapid growth of human population (but see below), expansion of agricultural land-use associated with both growth of population and commercialization of agriculture, use of modern earthmoving machinery and other modern technology, growing demands for raw materials and for food [especially high-quality animal protein), and an increase in urbanization and industrialization. Associated with these changes has been a tendency away from traditional patterns of sustained multiple use and toward increased specialization of use of land in ways that, for at least the short run, reduce the options for (or greatly increase the costs of) other uses (e.g., once a mangrove forest is converted to salt farms, the area is generally unsuitable for agriculture or regeneration to forest).

Mangroves, like highland forests, are generally considered "marginal," not in the sense of being unproductive but in the sense of being relatively remote and quite different from cities and farms. Even the terminology applied to mangrove forests let least in English) tends to be derogatory (man-groves are generally termed "swamps" rather than forests or fish hatcheries), whereas the discussion of mangrove destruction ["reclamation") tends to be euphemistic, implying or stating that the mangroves are wasted in their uncleared or undrained state.

The implications of research on population change, as well as of research on pollution, are that the major socio-economic, demographic, and ecological pressures on mangroves and other forest types come primarily from outside these zones, not inside. For example, although mangrove areas are not segregated in national censuses, it appears in Thailand that the human fertility of coastal districts where mangroves are found is no higher than the average for the province or region in which they are found (Pejaranonda 1985), and therefore natural population increase within the mangroves is unlikely to be the prime cause of pressure on mangrove resources. Other important causes of damage to mangroves that originate outside the mangrove zone include reduction of fresh-water flow associated with large-scale irrigation projects upstream (as in Bangladesh and India), central-government resettlement schemes which send people to settle in mangrove areas (e.g. in Indonesia), hydraulic mining which results in silt deposition in mangroves (e.g. in Malaysia and Thailand), urban growth, including the siting of large electric generators (e.g. in Australia, Indonesia, the Philippines, Singapore, and Thailand), and pollution from oil transport (e.g. in Indonesia, Malaysia, and Singapore).

Human Use of Forests: Mangroves and Uplands

Traditional patterns of human occupancy and use of mangrove forests in many ways resembles those of traditional swidden agriculturalists in the hills. Population density was low and settlements were relatively small. Technology was based on simple materials, minimal use of fossil fuels, and small numbers of tools. The use of the technology (e.g. in terms of fishing gear) was often ingenious and reflected an intimate knowledge of the environment. The traditional economy was largely self-contained. Long-term settlers in general had developed a conservative, self-sustaining adaptaion to the local environment. Studies of contemporary mangrove communites (e.g. Aksornkoae et al. 1984) suggest the continuing importance of subsistence production and home consumption of local products even in mangrove communities that are at least partially integrated into the market economy.

Social controls were based on a moral community, that is, consensus of the villagers regarding desirable goals, the appropriate ways of achieving them, and sanctions against those who violated norms. These norms tended to perpetuate the long-term conservation of the environment within which the people expected their descendants to live a life similar to the one they experienced.

Traditional use systems in the highlands as well as in the mangroves involved clear-cutting of patches. Under more conservative systems that did not destroy seed stock for regeneration and involved short periods of use followed by long fallow, there was natural regeneration of the forest when it was abandoned (Kunstadter, Chapman, and Sabhasri 1978; Saenger, Hegerl, and Davie 1983, chs. 4 and 5). Similar patterns were followed in mangrove forests that were carefully managed for long-term commercial exploitation, e.g. in Malaysia.

In the highlands wood from the cut forest was used as fuel to convert above-ground biomass to fertilizer for agriculture; in the mangroves, wood cut from the forest was used and often sold as fuel or as building material, and soil fertility was restored by infusions from upstream. Under conditions of low population density and a subsistence-oriented economy, both systems provided long-term sustained yield. Both systems generally involved multiple use of the varied forest environment at least for subsistence (e.g. hunting or fishing for food, collecting for minor food resources, building materials, and medicines).

In both systems the existence of a transitional zone between forested and non-forested areas is associated with increased species diversity, to the benefit of the human residents. In the highlands this is accomplished by successional forest regrowth after the swidden is abandoned or fallowed (Kunstadter 1979). The mangrove forest is itself a transitional zone between dry land and open ocean, which contains a richly varied environment.

Several socio-economic and ecological problems associated with economic development are common to highlanders and sea-margin dwellers. These include failure to protect the traditional inhabitants' interest in the land, damage to the environment as a result of the physical processes of development, harvest at rates far higher than natural replacement, emphasis on single uses that restrict employment rather than on multiple uses, and, in general, loss of traditional life-style.

Traditional patterns of land ownership and land use are often unrecognized by the authorities. The government claims the land as "forest" or "wasteland" which may be turned over to new owners or concessionaires for commercial exploitation or settlement. Although this may provide wage-labour opportunities for traditional inhabitants, commercial use as forest (which emphasizes short-run economic efficiency and profit) may not support as many people as were supported by traditional land-use systems. Aksornkoae et al. (1984, 11 -111), for example, show that the number of people employed in mangrove concessions is only about 17 per cent of those who actually live in mangrove areas. Moreover, the beneficiaries from jobs created by the commercialized exploitation of the mangrove forest are often outsiders, not the local people whose habitat is being destroyed Icf. Aksornkoae et al. 1984, 66).

Unless carefully controlled, the physical development processes (e.g. road-building) and large-scale logging or farming of forested land, both in the highlands and on the coast, may greatly reduce the ability of the forest to regenerate and may selectively change the character of the vegetation in favour of weedier (less useful) species. Overcultivation in the highlands has sometimes resulted in replacement of forest by grasses (Imperata or Saccharum) or bracken that inhibit forest regeneration and greatly increase costs of further cultivation. The analogous development in overused mangroves may be the spread of the fern Acrostichum, which inhibits the reseeding and regeneration of mangrove-tree species (Gan 1982; Srivastava and Khamis 1973; Srivastava and Sani 1979). Ecological problems (e.g. erosion) in the highlands are often associated with use of earthmoving machinery. In the mangrove forest, earthmoving projects which block waterflow patterns kill the mangroves as a result of change of water quality (see, e.g., Saenger, Hegerl, and Davie 1983, 35). Drying of the mangrove soils associated with some types of agricultural development may result in diminishing crop yields and virtually irreversible acid sulphate buildup (Hamilton and Snedaker 1984, 94-95; Saenger, Hegerl, and Davie 1983, 38).

There seems to be a strong association between commercialization of land use and costly, destructive ecological changes that generally do not occur under traditional subsistence uses. Great damage often occurs during the early stages of development, when the economy shifts from a sustainable subsistence system to an extractive commercial basis. In the highlands opium cultivators are generally much more destructive of forest resources and much less able to maintain yields on a given site than are subsistence cultivators (Kunstadter and Chapman 1978). In upland forests, commercialized timber harvesting has often been by high-grading (selective cutting of valuable species) without replanting, leaving vast tracts of low-quality forest. In the mangroves, large-block cutting without systematic replanting greatly increases the time needed for natural reforestation. Also in the mangroves the commercialization of fishing often leads to overfishing. The problem of assessing the costs and controlling the damage may be more difficult in the mangroves because the consequences are often geographically and socially remote from the places where the decisions are made and the environmental interventions take place. It is the fishermen, not the mangrove developers, who suffer directly from the loss of spawning grounds. This is a special example of "the tragedy of the commons" -i.e. the difficulty of exerting control for widespread public benefit over a resource that may be exploited for localized gain (Bromley 1985; Hardin 1973).

It is apparent that, once the pressures of modernization (e.g. in demands for cash and the material goods money can buy) spread from outside to the mangrove dwellers, the resulting changes take on a momentum of their own. In seeking the better things of modern life through commercialization, the descendants of the traditional mangrove settlers themselves may actively participate in the forces that destroy their environment. Community ethics break down, local inhabitants are no longer able to control the use and changes of their environment, the users (or despoilers) of the environment do not have to live with the immediate or long-term consequences of the changes, and the mangrove dwellers themselves can exert little or no influence over these changes.

The overall rate at which mangrove forest is being converted to other uses or made unsuitable for continued forest use may be on the order of 2 to 8 per cent per year (Sabhasri 1982). This rate is about the same as that for upland forests. If sustained, it leads to very rapid disappearance of the forests. About 40 per cent of the mangrove area of the Philippines was reported to have been converted to fish ponds between 1967 and 1978 (Hamilton and Snedaker 1984, 25-26; Saenger, Hegerl, and Davie 1983, 36ff.). About 200,000 ha of mangroves were reclaimed for agriculture in Indonesia in 1969 - 1974, with a much larger area reclaimed in 1974-1979 (Bird and Ongkosongo 1980). The potential for continued loss of mangroves is great because less than 1 per cent of the total world mangrove area is under some degree of preservation status (Hamliton and Snedaker 1984, 9). Because of the special problems of agricultural development in coastal zones (e.g. acid sulphate buildup), the "reclaimed" mangrove areas may become unsuitable for agriculture after a few years of cultivation.

Pressure on the remaining mangrove forest areas is often very great because they may appear to be relatively low-cost sites for construction of a variety of facilities, from salt farms, fish ponds, and rice fields to housing estates and industrial sites. If present socioeconomic and demographic trends outside the mangroves continue, these pressures can be expected to increase.

Management of the Mangroves

Most of these problems are now well recognized, and in recent years there has been a shift in research emphasis from basic descriptive studies to studies of management systems. Recent studies have often proceeded from several basic assumptions about the aims of management. These include combining some of the virtues of the traditional systems with the benefits of modern use - long-term sustainable yield, multiple use, reduction of environmental damage, and maintenance of the ecological benefits of the mangrove forest at the same time as economic goods are being taken from them for human use - and, in some areas, deliberate protection of mangroves in a relatively unmodified state (Burbridge and Koesoebiono 1980; Hamilton and Snedaker 1984; Knox and Miyabara 1984, chs. 6 and 7; Nature Conservation Council 1984; Philippine Council for Agriculture and Resources Research 1978, 71-128; Saenger, Hegerl, and Davie 1983, ch. 6). Management of mangroves may pose special problems, as compared with other ecological systems, for reasons already given, especially because of the important linkages of mangroves to other ecological zones.

Probably the most detailed integrated research on ecology, traditional patterns of human use, and modern management of mangrove areas for higher yields has been in Indonesia (e.g. Collier 1979; Hanson 1981; Hanson and Koesoebiono 1979; Koescebiono et al. 1979). Indonesia is a particularly appropriate place for this research because of the pressing need for agricultural land due to rapid population increase. Indonesia's long-term transmigration programme has sought, with mixed success, to relieve population pressures in Java through governmentsponsored migration to less-populated islands, especially Kalimantan and Sumatra. The destination has often been lands that are marginal for agriculture and poorly suited for traditional Javanese farming techniques. The work of scholars in Indonesia has described ecological problems, management issues, and some successful adaptations of traditional solutions, such as those of the Buginese, to coastal conditions. These studies can serve as a model for other areas in which there is a general lack of similar integrated research.

Characteristics of mangrove management systems

Discussion

Ecological characteristics of mangroves are in general fairly well known, but detailed information is needed on local and regional variations. This is important in discussing socioeconomic aspects of human settlements because mangroves have hinterlands with a great diversity of natural and socio-economic environments which exert a strong influence on ecological processes and human activities within the mangroves. Mangrove areas are transitional zones and are thus affected in many ways by inland and seaward conditions. The traditional socioeconomic systems that exploited mangrove resources were relatively small-scale and poor in technological equipment but often quite rich in intimate knowledge of the ecosystems. As economic development has advanced, technological influences over the mangrove environment have increased, but these have often been detrimental to the mangrove ecosystem. Except in Indonesia, few attempts have been made to describe traditional mangrove dwellers' knowledge and utilize it in designing management systems. This knowledge, together with the social organization by which it is implemented, is a valuable resource for reaching the management goals of sustained yield and multiple use.

In several respects the present socio-economic situation of traditional settlers in the mangroves resembles that of traditional marginal farmers of the upland forests. Both are now feeling the effects of large, scale socio-economic and demographic processes associated with modernization, urbanization, and socio-economic development, including commercialization of traditional activities, introduction of new demands for cash, loss of land, and damage to the ecosystem associated with development activities. Mangrove forests in Thailand were apparently being converted to other uses at about 6,350 ha per year between 1975 and 1979 (ch. 2, table 6, below). If conversion continues at the same rate, the mangroves will be reduced to about 75 per cent of their 1979 area by 1990, and only about 54 per cent will remain by the year 2000. Although there has been much discussion of the probable effects of the decline in mangrove areas on ocean fisheries and on forestry, to date little attention has been paid to the fate of the traditional mangrove dwellers when their forest has been heavily damaged or converted to other uses.

Likewise, although there has been considerable research on the effects of pollution on mangrove flora and fauna, there has been little attention paid to the biological or economic effects on human populations (e.g. with regard to direct toxic effects or to the saleability of mangrove products from contaminated sources). Another area that deserves further study is the effect of modification of mangroves on health conditions for diseases besides malaria (e.g., what are the consequences of increased population density on traditional methods of waste disposal?).

One of the limitations on research on the socioeconomic systems of the mangroves is the lack of basic information on who is living in the mangroves and what they are doing. Answers to these questions require field research, but it should also be possible to collect statistical information systematically if national governments geo-coded the data they routinely collect in censuses and other official surveys. Geo-coding {applying a designation to data to specify the geographical location from which it was collected, in addition to the administrative district) would allow detailed mapping of socio-economic and demographic data along with information which is already mapped, such as the distribution of mangrove forests or other ecological zones (see, e.g., Central Bureau of Statistics 1979; Prasartkul et al. 1980; Salih 1979).

The mangrove ecosystem and the socio-economic systems of mangrove residents are both greatly affected by processes and events beyond the geographical borders of the mangrove forests. This implies that it is appropriate for planners to take a broader than usual view when planning for the development of mangrove areas or when regulating uses of the mangroves. It also means that the ability to influence the future of the mangroves in the direction of sustained multiple use may be limited unless controls can be put on pollution and on economicdevelopment activities that affect the mangroves and their human populations. This may require the development of new community ethics with sufficient social and geographical scope to encompass both the social systems in which decisigns affecting environmental interventions in the mangroves are made and the mangrove zones themselves.

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