Some particular opportunities and constraints apply to agriculture in coastal areas and these can also have an impact on other coastal economic activities and ecosystems.
The following three particular types of opportunity are identified in Part A of these guidelines as being potentially important in the development of agriculture in a coastal area:
Opportunities dependent on natural resources. In many cases, coastal areas offer very favourable environmental conditions for agriculture. This is especially so where coastal areas consist of alluvial accumulation plains. Such areas generally have deep, relatively flat, fertile soils and benefit from a substantial supply of water, from surface and/or subsurface sources. The Batinah and Salalah coastal plains in Oman are a good example; they produce most of the agricultural output of that arid country.
Most coastal areas also have a milder and more humid climate than the interior as a result of the moderating influence of the sea, especially where favourable sea currents occur (e.g. the Gulf Stream along the western coasts of Europe). Such conditions may favour the growth of a particular crop or crops not grown elsewhere in the country.
In marked contrast to capture fisheries and natural forestry activities, coastal agriculture does not normally involve harvesting of coastal resources;1 its relationship with coastal ecosystems is usually more competitive (for instance, the expansion of agriculture into mangrove forests) and antagonistic (the modification of coastal ecosystems) than exploitative.2
Thanks to the diversity of coastal environments, which include both terrestrial and marine ecosystems, coastal populations often draw their livelihoods from a combination of agriculture and fishing, and sometimes also from seasonal work in the tourism sector (which can lead to agricultural labour shortages). Box B.1 describes two Vietnamese systems where agriculture, forestry and, in one case, fisheries are closely integrated.
BOX B.1Integration of coastal agriculture, fisheries and forestry in Viet NamTwo examples of farming systems in Viet Nam illustrate how farmers may develop local integrated systems involving crops, livestock, forestry and fisheries to use available resources effectively, gain advantage of complementary interactions and overcome the constraints faced by each subsector operating on its own.
Source: Hoang Hoe, 1991. |
Opportunities arising from location. Land and sea communications can also have implications for coastal agriculture.
When it is located near the coast, agriculture benefits from reduced transport costs for its produce compared to inland agriculture, whether export or domestic markets are targeted.
Coastal roads may give access to markets for agricultural products, and also facilitate input supplies. Improved roads may allow new areas of land to be brought into cultivation, and new water sources may also become accessible. However, roads in relatively isolated coastal areas are often poor, denying farmers market access or leading to produce reaching consumers in poor condition.
Even in the absence of good roads, produce can be shipped to markets by river as far as the coast and by boat along the coast. This may be the most significant locational advantage of coastal areas.
Derived or secondary opportunities. Coastal industries and development arising from special ecosystems and/or locational opportunities, may lead to population growth, thus providing derived opportunities for some types of agriculture, with increasing demand for food. When parts of the population are becoming more wealthy, there may also be increasing demand for higher-quality foodstuffs, such as fruit, vegetables, meat and dairy products. Industrial growth may also lead to increased demand for agricultural raw materials.
Tourism may also encourage demand for higher-value, perishable agricultural products, although this demand may not affect domestic markets as much as might be expected. In some small island countries, for example, large hotels are reported to import a high proportion of their food, whereas smaller hotels purchase most from local markets (FAO, 1992).
The impact of both types of increased demand on smallholder agriculture may be small and, as already mentioned, rising land values caused by the development of non-agricultural uses may result in insecurity for smallholders and tenants.
Constraints specifically affecting agriculture and agricultural development in coastal areas, arise principally from:
Proximity of the sea. Many coastal agricultural areas are flat, although others (for example volcanic islands and the Pacific coast of Latin America) may have steep coastlines. Low-lying agricultural land is frequently subject to severe drainage and soil salinity problems caused by high, more or less saline, water-tables, stagnation of rain and runoff water and flooding from rivers or periodic storm surges. There may also be physical damage from wind storms or tidal waves, and sensitivity to airborne salt deposition. Low-lying agricultural lands may also be susceptible to shoreline retreat and flooding as a result of coastal erosion, subsidence or a rise in sea levels which could result from global climatic change. Higher air humidity in coastal areas is favourable to the occurrence and propagation of certain plant diseases and pests that constrain crop growth. Even if the agricultural area is not directly affected, it may be taken over to replace land lost by other sectors.
Another important consequence of the proximity of the sea is the occurrence of tides that induce the penetration of sea water far inland in the lower reaches of most coastal water courses during high tides. This causes periodic increases in river water salinity that may preclude or complicate its safe use for irrigation. A good illustration of this is the coastal plain of the Limpopo river, near the city of Xai-Xai, in Gaza province, Mozambique.
In some special circumstances, the coastal climate may be very unfavourable to agriculture. A sizeable part of the coastal areas of Chile and Peru are deserts as a result of the negative influence of the Humbolt cold sea current.
Upstream effects. Supplies of surface water become available to coastal agricultural activities after they have already been used for upstream activities that influence the timing, quantity and quality of river flows. Upstream dams and irrigation schemes can deprive coastal areas of water for irrigation and, by removing silt and regulating floods, may affect the fertility of coastal alluvial agricultural land. Conversely, inland encroachment of agriculture on to forested land, slash and burn practices, overgrazing and inappropriate cultivation methods may increase runoff and erosion in catchment areas, with coastal land affected by increased sediment in rivers, lower dry season river flows and increased flooding. Thus, Bangladesh is highly affected by deforestation in the Himalayas several hundred kilometres to the north. The quality of surface water available to coastal agriculture may also be affected by upstream discharges of industrial and urban effluents and by drainage of chemicals and salts from agricultural land into rivers.
Water availability, use and upstream effects are a critical issue for agriculture (see Box B.2).
BOX B.2Water: a critical issue in coastal areasWater is a resource used for a variety of activities which provides: a medium for movement (not only of boats and logs but also of organisms, chemicals and particles); a habitat for aquatic life forms; and a potential source of harnessed power (hydroelectric dams). It can, however, also be a physically destructive force (tidal waves). Inland surface waters reach the sea via the coast where they accumulate in subsurface aquifers which are in dynamic equilibrium with adjacent sea/lake water. Inland and coastal agricultural activities may have a strong impact on water flows and quality, placing high demands on water and affecting catchment areas as the following illustrations demonstrate. Countries in the Near East, with growing populations, standards of living and industrial and agricultural activities, face increasing competition for limited water supplies. Surface water supplies are often limited by low rainfall, and coastal aquifers are a major water source. Groundwater extraction today tends to exceed the natural recharge rate, causing saltwater intrusion into the freshwater stocks. In Qatar, for example, the sea water interface is estimated to be advancing inland as fast as 1 000 m per year. The quantity and quality of water recharge to coastal aquifers may also be affected by the drainage of irrigation water and by the construction of coastal roads and their drainage systems. Saltwater intrusion into coastal aquifers has long-term impacts not only for the sustainability of coastal agriculture, but also for the availability of water to meet growing non-agricultural demand. Measures that may be taken to address these problems include: bans on drilling new wells and on increased extraction rates; improved efficiency in water use in irrigation; the cultivation of crops and cropping patterns with lower water demands; surface water management for improved groundwater recharge; the construction of physical barriers to saltwater intrusion; and the development of alternative freshwater sources (for example, imports or desalinization). There are various technical, financial, political and institutional difficulties associated with each of these measures. Saltwater intrusion is difficult to halt, and even more difficult to reverse. Belize, in contrast, has ample supplies of high-quality water in rivers draining forested mountains. There are, however, signs of degradation and potential conflict over water. Specific issues concerning agriculture involve growing demands for irrigation water for rice and sugar cane, discharge of organic waste from citrus processing plants, and increasing flooding and sedimentation in rivers (arising from the encroachment of agriculture into the upper forested watershed). This situation causes particular concern about potential adverse effects on the economic and environmental status of the coastal area, which supports an important fishing industry and a developing tourist trade. The killing of fish and damage to coral reefs have already been observed as a result of sedimentation and organic pollution of rivers. Measures proposed to address these problems include the establishment of a legal and institutional framework for water management and environmental protection, adoption of more efficient irrigation methods, development of drainage and water treatment facilities, and monitoring of water quality to control, prevent and remedy water pollution from agro-industrial effluent, agricultural chemicals and municipal waste. Source: Al Rifai, 1993; Belize, 1992. |
Space and resource constraints. Coastal areas are, almost by definition, of limited extension. The special opportunities they may present for agriculture (in deltas or estuaries, or processing and port facilities, for example) decline as activities are based further from the shore, the estuary or the port. Opportunities for expansion or relocation of such agricultural activities are therefore limited, especially when the coast is bounded by mountains. Agricultural development and population growth can only lead to physical concentration and pressures on resources such as water and land.
Space constraints and competition for land and water become more intense with urbanization. Many forms of agriculture require extensive amounts of land to produce relatively low-value outputs. As competition for land intensifies, agricultural activities such as grain crops and livestock grazing tend to be marginalized and replaced, either by non- agricultural activities or by agricultural activities with higher-value outputs, which require higher capital inputs and less land (for example intensive livestock raising or horticulture). Smallholders, unable to invest and intensify, thus tend to lose their land and migrate to the coastal towns.
Similar considerations affect irrigated agriculture where there is growing competition for water; irrigation uses high volumes of water, often inefficiently, to produce relatively low-value outputs. Increasing water scarcity may divert water away from agriculture to residential and industrial uses, and to other types of agriculture. Institutional arrangements for water fees, allocation and distribution ought to be introduced to encourage more efficient irrigation on higher unit-value crops.
Where the marginalization of low-value agricultural production is affecting peasant agriculture, this will lead to increasing pressure on a declining share of land unless non-agricultural employment opportunities are growing fast enough to absorb the labour displaced from agriculture. In any case, increasing pressure on land may lead to overexploitation, with inappropriate land use through the extension of agricultural activities into areas that may not be suitable for agriculture. This problem is not confined to coastal areas, but it may have particularly severe consequences if it affects coastal ecosystems (see Section 2.2.1).
Conversely, rapid development in other sectors may lead to competition for labour, although this is not a problem in many developing countries. If other sectors are perceived as more attractive, capital available for investment in agriculture may become scarce. There may also be competition for produce markets; good communications in coastal areas may facilitate imports of low-cost, high-quality agricultural produce with the consequent loss of outlets for local producers.
A number of general points can be made about the external effects of coastal agricultural activities on coastal ecosystems and other sectors:
The constraints already discussed occur largely as a result of agricultural activities suffering from one-sided or reciprocal competitive and antagonistic interactions. Under integrated coastal area management (ICAM) agricultural activities are also increasingly constrained by the need for control of their competitive and antagonistic effects on other activities and on special coastal ecological systems. These new constraints are common and must be a major consideration in the planning of agricultural development in coastal areas.
The discussion that follows concentrates on the effects of coastal agricultural activities. However, both inland and coastal activities may have a major impact on coastal ecosystems as a result of upstream processes. The profound influences of inland agriculture on the coast must therefore be recognized and addressed in coastal area management. The proximity of coastal ecosystems and coastal agriculture, however, leads to additional and stronger local interactions. These, as well as the more general upstream effects of both coastal and inland agriculture, are considered in this section.
Activity |
Environmental change |
Impact of social concern |
Estuary flood control, impoundment or diversion of coastal rivers |
Increased estuarine salinity, reduced circulation, sediment trapping, decreased supply of beach material to shoreline, shoreline erosion |
Reduced crop yields, reduced fish yields, increased water-borne diseases |
Agricultural pesticides |
Toxic pollution of estuaries and inshore waters |
Killing of fish, reduced fish yields, potential human consumption of toxic fish, coral pollution and loss |
Fertilizer use |
Increased amount of nutrients, eutrophication and pollution of estuaries |
Killing of fish, reduced fish yield, coral pollution and loss |
Overcropping or grazing in coastal watershed |
Watershed erosion, estuary sedimentation and increased turbidity, increased deposition in flood plains |
Corals and beaches covered with sediment, coral death, decline in fish yields, decreased recreation and tourism attraction, obstruction of navigation channels with sediments |
Irrigation from coastal aquifers |
Depletion of coastal aquifers |
Saltwater intrusion, contamination of groundwater |
Coastal wetlands reclamation |
Draining or dyking, physical destruction of habitat, toxic (acid) drainage, change in sedimentation patterns, change in water circulation/drainage, loss of coastal protection (mangroves), increased water-borne diseases |
Loss of wetland and forest/wildlife production, loss of biodiversitybiological diversity, loss or rarefaction of endangered species, killing of fish, reduced fish yields, increased storm damage and coastal erosion |
Intensive livestock activities |
Organic effluent, eutrophication and pollution |
Killing of fish, reduced fish yields, coral pollution and loss, reduction in recreation and tourism attraction |
Agro-industries |
Organic and toxic effluents, eutrophication and pollution |
Killing of fish, reduced fish yields, coral pollution and loss, reduction in recreation and tourism attraction |
Over-Overgrazing on coastal dunes |
Destabilization of dunes |
Initiation or increased dune migration on to agricultural or urban areas and on infrastructure |
Source: Extracted and modified from Sorensen and McCreary, 1990; and Barg, 1992.
Note: This table is only an indicative list of sketchily described impact chains and is not intended to explain, or list exhaustively, cause-and-effect relationships.
Table B.1 shows the main ways in which coastal agriculture can adversely affect coastal ecosystems and the natural resource-dependent activities related to them. In particular, the table shows that agricultural activities can have serious and damaging impacts on coastal ecosystems and on human populations. These impacts may result from resource depletion (such as loss of natural breeding areas or groundwater), from loss of habitat (with associated effects on biological diversity and on the productivity of natural resource-dependent activities), from hazards to human health (associated with contamination of water by chemicals or disease), or from loss of protection against coastal erosion or sand dune migration.
These issues are not unique to coastal agriculture, but are part of the more general problems of development in coastal areas, discussed in Part A of these guidelines.3
Dealing with such difficulties in a sustainable way is a major objective of ICAM. Minimizing the negative impact of agriculture must therefore be a particular concern to all involved with ICAM and with agricultural planning and management in coastal areas.
In keeping with the discussion in Part A of these guidelines,4 it is helpful here to distinguish four major processes through which agriculture may have a negative impact on other economic activities and coastal ecosystems:
Competition for land. Agriculture is the major occupier of land for cultivation and grazing. Associated settlement, buildings, roads and irrigation and drainage works take up still more land. In many coastal areas, significant clearing and drainage of coastal wetlands (swamps and mangrove forests) is taking place for cultivation. This may be the result of large-scale projects or continual encroachment by small-scale farmers. Such action results in habitat loss and loss of biological diversity, with wide-ranging effects on fisheries and, in the case of mangrove swamps, on forestry and wildlife. Since, in many cases, the soils of these wetlands are very difficult to manage, yields often decline dramatically after a few years and the land then has to be abandoned, creating pressure for further clearance, drainage and destruction of coastal wetlands.
Coastal wetlands and dunes may also be used for grazing. This may not necessarily result in direct destruction, but it may do if steady degradation continues over several years. Box B.3 describes the effects of grazing and movement of livestock on coastal dunes in Somalia.
Agriculture also suffers from direct competition for land for urban and other uses as mentioned above.5
BOX B.3Overgrazing and deforestation: coastal dunes in SomaliaThe Brava and Shamballot areas in Somalia suffer from destabilization of the Old Red Sand Ridge and the formation of shifting coastal sand dunes which are moving inland and encroaching on important irrigated cropland. The immediate causes of dune formation are wind and water erosion of denuded land. Denudation itself, however, is triggered by overgrazing, tree cutting for poles and fuelwood, and movement of livestock from coastal settlements across the ridge to inland grazing areas and back, as well as for nomadic pastoralistsÕ herds, from inland grazing areas across the ridge to coastal water sources. Dune fixation is extremely expensive. More fundamental measures are needed to address this problem, with an integrated, proactive approach to prevent dune destabilization. Such measures include the establishment of protected stock movement routes, the protection of scrubland from grazing and tree felling, the provision of access to alternative sources of water inland, and promotion of agroforestry systems providing fodder, fuelwood and poles. |
Competition for water. The effects of agriculture on competition for water are discussed in Section 2.1.2, but the use of water for agricultural activities affects other sectors too. Dams and irrigation schemes, inland or near the coast, may reduce surface flows, with effects on the timing as well as the overall volume of river flows. Irrigation and cropping activities in coastal areas may lower the water-table. Where irrigation systems extract groundwater from coastal aquifers these may become exhausted or, more commonly, become increasingly saline as salt water intrudes into them. Reduced or erratic surface and groundwater supplies in coastal areas can pose serious problems to coastal ecosystems, to aquaculture and to industrial and domestic water supply systems (see Boxes B.2 and B.4). Overexploitation of groundwater can also lead to subsidence and greater susceptibility to flooding.
BOX B.4Local effects of irrigation on fin-fish and shrimp farms in IndonesiaCultivation of fin-fish and shrimps in brackish water ponds is an important earner of foreign currency in Indonesia as well as an important strategy for improving farmersÕ living conditions in lowland reclamation resettlement areas. The ponds are located along the coastline and supplied with fresh water from the irrigation system. However, water is supplied irregularly, according to overall availability, crop water requirements and irrigation system shutdowns for maintenance. Irregular water supplies constrain production in the ponds and hatcheries and, in addition, water supplies are frequently polluted by the return irrigation flows. Quality and quantity of production, as well as export acceptability, are adversely affected by these problems. It is estimated that, with improved freshwater supplies, a 15 to 25 percent increase in production from existing ponds could be achieved, corresponding to about 50 000 tonnes of exportable shrimps and the creation of 150 000 to 200 000 additional jobs. Without proper water management there is the risk of groundwater contamination and degradation of adjacent land from brackish water infiltration from the ponds. |
Antagonistic effects. The most pervasive antagonistic effects6 of agricultural activities tend to be related to water flows. Coastal ecosystems are highly dependent on water, are often sensitive to changes in water quality or quantity, and are located downstream of inland and coastal activities using and discharging fresh water. Moreover, water supplies for residential and industrial users in coastal areas are also often limited.
Intensive agricultural activities Ð usually related to export-oriented rather than subsistence crops Ð may result in water pollution through runoff of agricultural chemicals. The closer the use of agrochemicals to the coastal area, the higher the risk of it having a negative impact on coastal ecosystems and the more difficult the protection of the area. Similar risks are associated with intensive livestock enterprises and agro-industry.
Soil erosion, which has many causes, increases sediment in watercourses which can silt up ports and cover coral reefs. Conversely, dams trap sediments needed to fertilize coastal areas such as swamps. Dykes and polders trap fresh water required in coastal wetlands. Poorly managed irrigation can lead to saline runoff, or the release of toxic substances that find their way to the coast.
Changes in water quality may have far-reaching effects. Increased sediments in water, for example, are damaging to coral reefs which require clear and clean water (see Boxes B.2 and B.5), but reductions in sediments are damaging to coastal wetlands dependent upon periodic recharge with imported nutrients and organic material. Toxic chemicals and organic wastes in surface water damage, and may destroy, sensitive coastal ecosystems. Downstream aquacultural enterprises may also be damaged, with fish death, reduced productivity or contamination of produce (see Box B.4). Surface or groundwater supplies for domestic uses may also be contaminated. There may be wider health implications too; in some parts of West Africa falling salinity of previously tidal swamps has resulted in the spread of insect- and water-borne diseases.
BOX B.5Local effects of agricultural degradation on coastal fisheries in the PhilippinesThe Central Visayas region in the Philippines provides a dramatic illustration of both direct antagonistic effects and secondary socio-economic effects linking agricultural intensification to coastal ecosystems and the livelihoods of rural coastal people.
|
Physical disturbance of coastal ecosystems may have other antagonistic effects that do not involve water flows. Many animal species require different habitats at different stages of their life cycle, and need to migrate between them. Disturbance or development in relatively small coastal areas may interrupt migration routes or specific breeding or nursery areas.
Secondary (socio-economic) effects. Table B.1 specifically excludes the secondary effects of agricultural development. These include increased settlement and population growth which in turn can affect the local environment. They may also threaten coastal livelihoods, increasing poverty and forcing people to overexploit the remaining resources available to them (e.g. by draining wetlands, destroying forests, overfishing).
With increasing political and economic interest in environmental protection there is growing pressure to assist farmers in avoiding the negative external effects of agricultural activities. Clearly this requires full information about these effects and, in the light of this information, appropriate planning mechanisms and interventions.
Action |
Benefit |
Reduced competitive and antagonistic effects | |
More efficient irrigation systems |
Increased water availability for other sectors |
Cropping varieties and practices giving higher and/or sustainable yields on suitable land |
Increased land availability for other sectors: less cultivation of steep erodable slopes and less clearing and drainage of wetlands |
Less cultivation on steep slopes, controlled grazing, conservation practices, appropriate manuring methods, integrated pest management methods |
Improved water quality: reduced erosion and nutrient leaching, reduced organic and chemical pollution |
Positive secondary effects | |
New enterprises or higher productivity leading to improved livelihoods from agriculture |
Reduced exploitation and more sustainable use of fisheries and wetlands |
Increased general economic activity | |
Increased food supplies, demand for agricultural inputs and services, supplies of raw materials for processing, export |
Increased incomes, nutrition, employment and wealth in other sectors reducing pressure on fisheries and wetlands |
Note: Potential beneficial impacts are shown, but actual impacts will depend upon the nature of changes and on political, economic and social structures.
There are a number of ways in which appropriate agricultural development can have positive impacts on coastal ecosystems. An appreciable contribution will stem merely from reversing or reducing the competitive and antagonistic effects of existing agricultural activities, for instance by the adoption of irrigation systems or crops that use less water, or crop protection methods that do not rely on persistent biocides. Higher and more sustainable productivity on existing agricultural land may reduce pressures to bring new land under cultivation.
Appropriate agricultural development can also have positive secondary effects, for instance, providing improved livelihoods for rural people can reduce pressure on coastal fisheries and wetlands. Agricultural development may increase the general level of economic activity in a coastal area. Increased demand for agricultural inputs and services and consumption goods and services, and increased supply of food, export crops or industrial raw materials will all contribute to the local economy and stimulate growth and employment in other sectors, with positive secondary effects.
Unfortunately, while higher levels of economic activity in a coastal area can lead to improved livelihoods and reduced pressure on coastal fisheries and wetlands, and can generate wealth for investment in the protection of coastal ecosystems, all too often increasing levels of economic activity in rural coastal areas lead to increasing pollution problems without any easing of the pressure on coastal fisheries and wetlands. Similarly, higher sustainable crop yields can reduce the demand for new cultivated land, but they can also make crop production more attractive and increase the demand for agricultural land. The effects of agricultural development are thus very sensitive to the nature of development and to economic, social and political structures and circumstances. This point will be treated in more detail later in Section 3.2.2 when discussing strategies and interventions that may be used to promote appropriate agricultural development.
1 Cutting fodder from mangrove forests for livestock and the use of dried fish or seaweed as fertilizers are some exceptions.
2 For explanations of various relationships, see Part A, Section 1.5 and Box A.1
3 See in particular Part A, Section 1 and Table A.3.
4 See Part A, Section 1.5.
5 See `constraints' in Section 2.1.2.
6 See Table B.1.
7 See Table B.2.
