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2. Interactions

One of the prerequisites of ICAM is the proper identification of the interactions between the coastal forestry sector and other sectors and ways and means to enhance/reduce them. It should, however, be emphasized that the knowledge of such interactions remains incomplete. Ecological research continues to yield new information on interactions between animals and plants within the forest ecosystem, while the impacts of current and future innovations in technology and the resulting changes in use patterns are inherently unpredictable. These impacts may not manifest themselves for many years - especially in the forestry sector with its very long life or production cycle - and the effects, when manifest, may be difficult to attribute to a single cause. Some of the known interactions involving the coastal forestry sector are described below.


2.1.1 Overall economic development

Depending on its relative importance, the coastal forestry sector may provide a stimulus for overall economic development of the coastal area, and could even have an impact upon the economic development of the whole country. Among the potential benefits of sound management of coastal forests is the provision of employment and additional income opportunities for rural people. Coastal forests can also generate foreign exchange through the export of wood and non-wood forest products. Overall economic development may in turn increase the demand for forest products and thereby benefit the forestry sector (or conversely lead to overexploitation).

2.1.2 Fisheries sector

Coastal forests (see Section 1.1) provide leaf litter and detritus for the aquatic food web, in addition to spawning grounds and shelter for various fish and shellfish. The mangrove oyster (Crassostrea tulipa) for instance grows on the stilt roots of the Rhizophora species. In many developing countries, fishing communities rely on wood from coastal forests for cooking, smoking fish, building materials, boat-building and fishing stakes (see Figure C.2).

Figure C.2
Mangroves and fisheries

Source: Kapetsky, 1986.

Moreover, the mangrove waterways provide an ideal location for small- to medium-scale cage, raft and bottom culture for fish, crabs, lobsters, cockles and oysters. Capture fisheries is also often undertaken on a subsistence basis in the creeks and rivers of coastal forests and in flood plains. The fisheries and forestry sectors may also share the transport infrastructure of the coastal area.

2.1.3 Agriculture and food security

A combination of forestry and agriculture on the same land can be undertaken, and provides mutual benefits. Several different types of agroforestry systems exist.8 An illustration of the beneficial roles single trees and patches of forests have in maintaining or improving the agricultural carrying capacity of flood plains is given in Box C.4.

Benefits of single trees or patches of trees for agriculture

An illustration of the beneficial role single trees and patches of forests have in maintaining or improving the agricultural carrying capacity of flood plains is given by the following example of the restoration of seriously degraded flood lands in the Mekong delta in Viet Nam.

Melaleuca leucadendron, a tree 10 to 20 m tall, once covered an area of 250 000 ha in low-lying, seasonally inundated areas in the Mekong delta in Viet Nam. Years of unmanaged harvesting for fuelwood and the clearing of land for other uses gradually reduced and degraded the Melaleuca forests. During the war in the 1960s and 1970s, a large portion of the Mekong delta was drained and burned. Once the soil dried out, sulphur rose to the surface, reducing the soil pH to 3.9 or lower. Crops, including rice, could not be grown and local people were forced to leave. After the hostilities, local people made tremendous efforts to restore agriculture on the plain. In so doing, they came to realize that the pH of the soil had to be increased. This could only be achieved through watering the soil with fresh water and planting trees. Fresh water was brought on to the plain by new canals, and millions of Melaleuca trees were planted on the most acid soils, since it was the only species that would grow in these conditions. This massive tree planting activity has made the area prosper again also as farmland. In addition, native plant and animal species are gradually returning to the plain. Not only freshwater fish, but also turtles and especially water birds have returned in surprising numbers, thus once again providing a source of food and additional income to local people.

In addition, coastal forests protect agricultural land from the actions of winds and waves. In Guyana for example, 90 percent of the population live in a narrow coastal area and the agricultural production from this area accounts for 70 percent of the country's GDP. Mangroves used to protect large parts of this low-lying coastal area, but the mangrove belt has deteriorated, as a result of overexploitation and clogging up of the mangrove pneumatophores with silt originating from the Amazon, necessitating the establishment of expensive sea wall defences (FAO, 1990).

In many coastal areas without natural forest cover, narrow strips of forest are established to protect agricultural land and crops from winds loaded with salt and sand particles; large plantation programmes are often undertaken in areas prone to the encroachment of moving sand dunes. Forests also provide fodder for livestock as well as building and fencing materials.

Animals living in forests contribute to the pollination of crops. For example, several types of pollinating bees and wasps build their nests in the coastal forests and another well-known example is that of the Malaysian cave fruit bat (Eonycteris spelea), the only known pollinator of the commercially important durian (Durio zibethinus).

Coastal forests also contribute directly to food security by providing game and many other edible forest products such as fruits, nuts and fish. In many countries in arid regions, mangrove forests represent the last remaining wood resource in the coastal area.

2.1.4 Tourism and recreation

When well tended, coastal forests provide additional attractions and recreational facilities that can increase the tourism potential of the coastal area. Lowland rain forests harbour a great number of plant and animal species which may attract tourists, a beach forest may provide welcome shade, and the unique features of the mangroves or other swamp forests may attract both local and foreign nature tourists.9

Activities that are compatible with coastal forest and wildlife management and that may be promoted in coastal forested areas are nature trails, bird watching, botanical studies, nature photography, fishing and river rafting/canoeing/kayaking.

2.1.5 Human settlements

Protection against storms and coastal erosion and the provision of recreational facilities, employment, building materials and fuelwood are some of the positive interactions between human settlements and coastal forests.

2.1.6 Infrastructure

Forest-based operations can lead to road building and the development of other essential infrastructure works such as ports. Many of the present harbours along a sea shore or river bank originated as timber loading points. In the tropics, mangroves trap sediments and thereby reduce the risk of siltation of shipping lanes and harbours caused by upland deforestation. The coastal forestry sector in turn benefits from access to low-cost marine and inland river transportation systems and from other infrastructure developed to serve the agriculture or fisheries sector. Of course, opening up areas for forestry can also have unwelcome negative effects.

2.1.7 Environment

The wise management of coastal forests will contribute to an improved environmental situation in the region. This is especially valid in erosion-sensitive and mountainous coastal regions. Forest and wildlife management may also contribute to the conservation of the diversity of existing and potential genetic resources. Restoration of degraded areas through tree planting can also contribute to an improved environment.


As population densities increase, natural resources in coastal areas are subject to high demand and are also facing a larger number of different kinds of user activities. These uses are often incompatible, may result in a wide array of problems and conflicts for coastal resource users and pose difficult choices to decision-makers.

2.2.1 Competitive interactions

The main conflicts stem from competition for land, water, forest products and services for human settlement, agriculture, fishing, forestry, industry, trade, infrastructure works, tourism and amenities between private industries and local people and even between government agencies themselves. The situation is aggravated by the absence of proper coastal land-use planning.

As explained in Part A,10 negative interactions can be competitive or antagonistic. Examples of competitive interactions between the coastal forestry sector and other sectors are given below.

Fisheries. The conversion of mangrove areas for aquaculture ponds on a large scale in many tropical countries, in particular in Asia but also in Latin America, is a prime example of the competition for land between the forestry and the fisheries sectors.

Agriculture. Many swamp forests and some mangroves have been cleared for cultivation of rice and other agricultural crops because of competition for land. Use of river water for irrigation purposes may severely limit the amount of fresh water reaching the coastal area and this may adversely affect the viability of mangroves and temporary swamps. Browsing camels, goats and other livestock may damage trees and other forest resources. The establishment of plantations of rubber, oil-palm or fast-growing timber species may in turn decrease the amount of land available for agricultural purposes.

Mining. Peat, sand and other minerals may be established on forested land and destroy the forest or deny access to users.

Tourism and recreation. Intensive, single-species forestry does not provide the type of forest sought for tourism and recreation; not only are such forests not diverse in tree species but wildlife also becomes scarce. Conversely, intensive levels of use of coastal forests for nature tourism and recreation may cause wildlife disturbance, soil compaction or erosion and trampling of rare plant communities.

Other sectors. As a result of the strategic location of coastal areas, pressures on land for human settlements, ports and other infrastructure, industrial and tourism development can become far greater than it is further inland, placing increased pressure on the remaining natural ecosystems.

Unfortunately, the low value placed on many of the coastal forests (measured only in terms of the value of wood production) means that they are at a disadvantage when decisions on land-use allocation are made. The largest threat currently facing the existing mangroves in the state of Johore in southern peninsular Malaysia for instance, stems from plans to build a second port, a second link to Singapore, an industrial estate and several marinas and residential estates, all requiring the release of land at present classified as mangrove forest reserve; these plans have already been approved or are likely to be in the near future.

2.2.2 Antagonistic interactions

Antagonistic interactions between the coastal forestry sector and other sectors include direct and indirect effects on the forestry sector and adverse effects caused by the sector.

Damage caused by conversion to other land uses. Where conversion of coastal forests takes place, even though individual areas converted to other uses may be small and the effects thus deemed insignificant, the cumulative effects of a fragmentation of the coastal forests on forest resources and biological diversity may in fact be severe. As a result of strong links with other ecosystems and the many products and services that can be obtained from coastal forests, adverse effects of such conversions extend to other sectors as well.

Damage caused by pollution of water and air. Port and other infrastructure development, industrial and household waste disposal, oil exploitation, mining, dredging and filling may severely disturb, or even destroy, coastal or riverine forested ecosystems as a result of the release of chemical and physical pollutants, including agricultural chemicals, organic waste and untreated aquaculture pond water or acid drainage water, into the air, or into rivers and coastal waters. Chemical pollutants may kill the plants and animals directly or through accumulation in the food chain.

Damage caused by changes in water flow. Such damage may be caused by structures erected to protect the coastal area against erosion from the sea or to control the flooding caused by upland rivers. Changes in water currents may also be caused by dredging and filling. Many wetland and mangrove areas have been destroyed as a result of the construction of coastal protection structures. Such structures can result in large areas of productive wetland and tidal flats being sealed off from marine influences or can deprive the seaward areas of the estuary or lagoon of fresh water. Thus, not only are these protection efforts not always successful, but they also destroy highly productive natural ecosystems. The Farakka dam in India for instance, is blamed for changes in the forest structure in the western part of the Bangladesh Sundarbans mangroves, because of a decrease in the amount of fresh water reaching the forest in the dry season.

Adverse effects of inappropriate coastal forest and forest industry management. Some of the most noticeable and severe effects occur as a result of the clearing of forests. Where this occurs inland along rivers, it often results in increased flood hazards affecting both human settlements and agricultural land. In also usually leads to an increase in the sediment load of rivers and coastal waters through soil erosion and this may adversely affect riverine and coastal fisheries, sea grass beds and coral reefs and may cause siltation of harbours and shipping lanes. Forest clearance along the coast deprives it of protective cover against storms and tidal floods and can open the way to erosion of coastal land by wind and water, intrusion of salt water and/or the destabilization of sand dunes. Valuable spawning and feeding grounds for aquatic species may also be lost when mangroves or riparian forests are cleared. The local population will be affected by a shortage of forest products.


There are also interactions within the coastal forest sector. Natural forests and plantations may improve the microclimate for other plants and provide habitats for many plant and animal species. Animal species may contribute to pollination and seed dispersal, helping to maintain forest biological diversity. The establishment of forest industries may contribute to increasing demand for timber and other forest products. But it may have adverse effects on the forest ecosystem.

Forests can also be managed with a view to sustainability, such as conservation of soil and water, and biological diversity, and the enhancement of service provided for other sectors.

As far as competitive interactions within the sector go, felling of natural forests, or draining swamps for plantation crops (e.g. oil-palms, coconut) are typical examples. Even antagonistic interactions exist within the forest sector: conversion of natural forest to forest monoculture reduces biological diversity, degrades and destabilizes ecosystems, and reduces soil fertility; opening up of roads into coastal forests will facilitate the encroachment of farmers on to forest land with many potentially harmful effects; and dragging of logs removes topsoil and damages natural vegetation and seed-bearers.

Choices will have to be made between conflicting objectives such as maximizing wood production and increasing the stock of wildlife (see Box C.5). Conflicts will also arise between industrial users of the forest and forest dwellers or those who depend on the forest for their livelihoods. Box 6 gives an example of benefits derived from properly managed coastal forests. Table C.2 summarizes the main forestry-related interactions.

Sustained yield forest management

The Matang Mangrove Forest Reserve in Malaysia has been under intensive management since the beginning of the century. The forest is regulated in the appropriate even-aged classes and harvested stands are immediately replanted or, to a limited extent, regenerated naturally; forestation of marginal areas incorporated into the reserve is undertaken exclusively by means of plantation.

Monitoring of the permanent sample plots installed in the reserve has not shown any decline in yields over three rotations (Haron 1981). The incorporation of marginal areas by canalization and plantation has increased the size of the management area over the years. It must therefore be concluded that sustained yield forest management is feasible for at least three rotation periods of 30 years.

With complete crown cover and immediate regeneration of harvested areas, the production of litter fall from the managed forest has been found to be superior to that of natural untouched stands (Ong et al., 1982). Litter fall is an important source of energy in the food web that affects fisheries and other living mangrove-dependent organisms. No significant decline of commercial catches of fish, molluscs and shellfish in the coastal waters adjacent to the Matang Reserve has been reported during the management period.

It would seem most likely that the biological diversity of the original mangrove has been affected in the regulated parts of Matang since only a few preferred species have been used to regenerate harvested areas. Consequently, with this type of management, areas should be set aside in the initial planning stage as reserves managed for their genetic resources rather than for commercial wood production.

Source: FAO, 1994a.

Positive environmental effects of sound forest management

In the Sundarbans mangroves in Bangladesh, where around 400 000 ha is managed, many species are utilized (sawnwood is a major product) and natural regeneration is promoted.

The regeneration system should maintain biological diversity, but the inherent complexity of the system also makes it difficult to assess if this has in fact happened, although it is assumed that it has. The chief advantage of the forest management of these mangroves is that they have been retained at all. As elsewhere in the tropics, there has been pressure to convert the Sundarbans mangroves to food production, i.e. fish ponds, shrimp farming and agriculture, and to human settlement. The fact that such an extensive area of mangroves is still in existence today, in a country with one of the highest population pressures in the world, is largely the result of the fact that a significant part of the mangroves were reserved at an early stage for forest management.

Nowhere in the world are mangroves more important for the protection of human lives and activities than in the Bay of Bengal, which is periodically affected by typhoons. Consequently, it can be claimed that the management of these mangroves has had a positive impact on the environment.

Natural water-borne feed is also still available for fish and shrimp farmers in the Sundarbans, unlike in some other parts of the world (e.g. Ecuador), where heavy deforestation of mangroves, which are not subject to management, has made it necessary for shrimp farmers to resort to artificial feed in recent years.

Source: FAO, 1994a.

Forestry-related interactions


Types of interaction


Positive interactions


Overall economic development

Stimulation of coastal area development, employment, export of forest products, tourism

High employment percentage in Bangladesh Sundarbans


Provision of leaf litter and detritus for the aquatic food web, spawning grounds for fish, supply of wood (for cooking, fish smoking, boat- and house building) to fishing communities, ideal location for fish culture

In peninsular Malaysia, 30 percent of fishery production is associated with mangrove ecosystems


Protection of agricultural land from wind, sand and waves, improvement of carrying capacity of flood plains, provision of fodder for livestock, pollination by forest-based insects and birds, provision of game, edible and medicinal products, provision of fencing materials

In Guyana, where 90 percent of the population live in a narrow coastal area, the deterioration of the mangrove has necessitated the building of expensive sea wall defences

Tourism and recreation

Provision of shade on beaches, unique natural features to visit, excursions, bird watching, fishing, river canoeing

Proboscis monkeys in Borneo, royal Bengal tiger in Bay of Bengal, the milky stork

Human settlements

Protection against storms and coastal erosion, recreational activities, building materials



Maintenance of roads and ports, protection of ports through reduced risk of siltation



Protection against erosion in mountainous coastal areas, conservation of biological diversity, restoration of degraded areas through reforestation, favourable microclimate and habitat to numerous plant and animal species

In Viet Nam, mangroves are planted as a protection measure against wind and waves. In Denmark, coastal forests have been planted since 1830 to stabilize the sand dunes that had moved inland and covered several villages

Complementary interactions



Shared transport infrastructure



Agroforestry, shared transport infrastructure


Tourism and recreation

Protection of forests to promote tourism, research


Competitive interactions



Conversion of mangroves for aquaculture



Clearing of swamps for agricultural production, irrigation that deprives coastal forests of fresh water, livestock grazing may damage forest resources, use of agricultural land for fast-growing forest plantations

Most periodic swamp forests in alluvial plains of Asia have been cleared for wetland rice cultivation


Peat, sand and other mineral extraction which can destroy forests


Tourism and recreation

Single-purpose forest exploitation that reduces attractive flora and fauna species diversity, disturbance of wildlife, soil compaction, destruction of rare plant species by intensive tourism


Other sectors

Land requirements for other economic development

Johore state, Malaysia: likely release of land classified as mangrove forest reserve for this purpose

Antagonistic interactions


Direct adverse effects

Forest conversion to other land uses or to forest monoculture

Even conversion of small forest areas can have considerable adverse effects on biological diversity, soil fertility and ecosystem stability

Indirect adverse effects

Air and water pollution caused by disposal/leaching of household aquaculture, agriculture and industry waste, oil spills and mining

Eutrophication, clogging of mangroves, acid rain

Effects of poor management

Changes in water flow caused by dams, irrigation schemes, dredging, landfilling, coastal protection structures, clearing of forests

Destruction of wetlands and tidal flats, erosion leading to siltation, destruction of coral reefs and spawning grounds

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