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The coastal zone is essential to marine life and supports a large part of the world's living marine resources, certainly more than the open sea. Its wetlands, lagoons, seagrass beds, coral reefs and shallow bays are nursery or feeding areas for most coastal and many oceanic species. This zone has the highest biological diversity of any part of the sea.

While the whole ecosystem is the focus of management, each of its structural parts and essential processes must be conserved - with the emphasis placed on critical areas. For example, the mangrove forests, tideflats, beaches, seagrass or kelp beds, and coral reefs need special attention.

3.1 Critical Habitat Resources

Although ICZM programmes are created primarily to manage physical development, they have to be based upon detailed knowledge of resource vulnerabilities and a candid examination of conservation issues.

In tropical countries - to which this book is oriented - ICZM conservation programmes may be centred on the following “critical habitat” types: mangrove forests, coral reefs, submerged seagrass meadows, beach-dune systems, and lagoons/estuaries (including embayments) known to be especially valuable. With conservation of these five habitats as a priority, it is necessary to understand their vulnerabilities and conservation needs.

While it is useful and practical to focus on individual habitat types, one must not forget that they exist only as components of wider coastal systems; therefore, they should be managed as parts of a greater system (see 3.1.7).

3.1.1 Mangrove, Wetlands and other Intertidal Systems

Some 24 million hectares of mangrove forests occur in coastal areas of subtropical and tropical countries of the world. Mangroves are found along sheltered coastlines where wave activity tends to be minimal. The term mangrove refers to any of dozens of species of trees capable of living in saltwater and salty soil regimes (Figure 3. 1).

Ecologically, mangrove communities have a variety of recognized roles in the areas where they occur. A prominent role is the production of leaf litter and detrital matter which is exported to lagoons and the nearshore coastal environment. The organic matter exported from the mangrove habitat is utilized in one form or another by the inhabitants of estuaries/lagoons, near-coast waters, seagrass meadows, and coral reefs which may occur in the area. Most tropical commercial shrimps and many fish species are supported by this food source. Over 30 percent of the fisheries of Peninsular Malaysia (about 200 000 t) are reported to have some association with the mangrove ecosystem.

Mangrove ecosystems also provide a valuable physical habitat for a variety of important coastal species. Waterfowl and shorebirds are well known and highly valued inhabitants of wetlands, as are alligators and muskrats. Less evident, but equally important inhabitants are crabs, shrimp, and the important juvenile stages of commercial and sport fishes, along with numerous forage species of fish and invertebrates (Clark et al., 1980).

Figure 3.1

Figure 3.1 Five Mangrove Forest Structural Types Source: Snedaker and Getter (1985)

Shoreline mangroves are recognized as a buffer against storm-tide surges that would otherwise have a more damaging effect on low-lying land areas. Littoral strip mangroves planted by the Bangladesh Government in the 1980s are credited with saving thousands of lives and millions of dollars worth of property during the cyclone of 29 April 1991 that ravaged the southeast coast of the country. Also, mangroves are often noted for their ability to stabilize coastal shorelines that would otherwise be subject to erosion and loss. Conversely, if left in place they can pre-empt development sites that are at too low an elevation and are hazardous real-estate sites.

The value of the mangrove resource in terms of its marketed products can be expressed in economic terms. The “free” services provided by the mangroves are more difficult to measure and consequently are often ignored. These “free” services would cost considerable energy, technology and money to be provided from other sources. Since this is seldom taken into account, the total value of the mangrove resource is usually quite significantly underestimated (Hamilton and Snedaker, 1984).

In general, the mangrove ecosystem is fairly resistant to many kinds of environmental perturbations and stresses. However, mangroves are sensitive to excessive siltation or sedimentation, stagnation, surface-water impoundment, and major oil spills. These actions reduce the uptake of oxygen for respiration which results in rapid mangrove mortality. Salinities high enough to kill mangroves (+90 ppt) result from reductions in the freshwater inflow and alterations in flushing patterns from dams, dredging, and bulkheading. Lowered salinities from seawalls and coastal structures and restriction of tidal flow also kill mangroves. On the other hand, mangrove forests help maintain coastal water quality by extracting chemical pollutants from the water.

A major problem that affects mangrove habitats results from man's desire to convert mangrove areas to residential, commercial, industrial, and agricultural real estate by land filling. In addition, there is an increasing demand for forest wood products that results in the exploitative clear-felling of the forests.

3.1.2 Seagrass Systems

Submerged seagrasses are often abundant in the shallow waters temperate and tropical coastal environments of the world. Seagrass beds, or meadows, are highly productive and valuable resources which enrich the sea and provide shelter and food for some of the most important and valued species of fish and shellfish.

Seagrasses grow best in the quiet, protected waters of healthy estuaries and lagoons, often in beds, or meadows, that are easily delineated for classification as critical habitat areas. They are normally found in shallow areas where light can readily penetrate and enable photosynthesis to occur. Seagrass beds extend shoreward to the point where wave action prevents them from rooting.

High productivity of seagrass habitats is associated with both seagrass growth and the production of “epiphytes” attached to the leaf surfaces. For example, primary productivity (amount of plant production) for two common seagrass species has been shown to be higher per acre than for average corn and rice cultivation in the USA.

Seagrasses intermingle with both mangrove and reef communities at their respective seaward and landward boundaries. Submarine meadows of seagrass frequently provide the link between mangrove and coral reef ecotypes (Figure 3.2). The migration of animals at various life stages from one ecosystem to another for feeding and shelter, coupled with currents that transport both organic and inorganic material from runoff and tidal flushing, ties the offshore coral reefs to nearshore seagrass beds, and the seagrass beds to mangrove estuaries (Berwick and Chamberlain, 1985).

Wherever they do occur, seagrass meadows are essential elements of coastal ecosystems. Although seagrasses are little used for commercial purposes, they play an important ecological role, providing a substantial amount of nourishment, nutrients, and habitat. These meadows provide vital places of refuge not found in the open ocean. They attract a diverse and prolific biota and serve as essential nursery areas to some important marine species. Seagrass meadows are also known to trap and bind sediments, thereby reducing particulate pollutants.

Seagrasses are a relatively hardy group of plants, but they are damaged by unfavourable conditions such as excessive siltation, turbidity, water pollution, bottom trawls which scrape and plough the meadows, and marine excavation and filling. Some pollutants in seawater are toxic to seagrasses. Other major threats are dredging and filling operations in seagrass meadows. The disappearance of seagrass communities may go unnoticed because, unlike mangroves and coral reefs, seagrass communities are not visually obvious to most observers.

3.1.3 Coral Reef Systems

Coral reefs occur along shallow, tropical coastlines where the marine waters are clean, clear, and warm. They are one of the most productive ecosystems in the world. The basis for the high productivity of the coral reef ecosystem is a combination of the production of the reef with support from its surrounding environment.

“Fringing” reefs - those contiguous with the shore - are the most common and widespread of the reef structural types; they are most usually found below the low tide level. Their inshore distribution renders them more susceptible to degradation from coastal activities than other reef types. One of the largest fringing-reef formations lies along the Saudi Arabian, 1 100-mile Red Sea coast which is noted for an absence of freshwater (and sediment) runoff (Clark, 1986; Ormond, et al., 1985; Snedaker and Getter, 1985).

“Patch” reefs are isolated and discontinuous bits of coral reef, often lying shoreward of offshore reef structures. “Barrier” reefs are linear, offshore reef structures that run parallel to coastlines and arise from submerged shelf platforms; the water area between the shore and reef is often termed a “lagoon”. The world's largest barrier reef system, the Great Barrier Reef, occurs off the Queensland coast of Australia. The areas of greatest coral reef development are the Western Pacific and Indian Oceans and, to a lesser extent, the Caribbean Sea, including Belize and the Bahama Islands.

Figure 3.2

Figure 3.2 Interactions Among Three Major Tropical Habitats of the Coastal Area. Source: Ogden and Gladfelter (1983)

Coral reefs have important economic outputs. For example, they contribute to fisheries of three types: fishing directly on the reef; fishing in shallow coastal waters where coral reefs support food webs, life cycles, and productivity; and fishing in offshore waters where the reef's great productivity may contribute to support of “high seas” fishes. Approximately one third of the world's fish species are said to live on coral reefs (WRI, 1986). Artisanal fisheries dependent on coral reefs have been reported to account for up to 90 percent of the fish production in Indonesia and up to 55 percent of production in the Philippines (providing 54 percent of the protein intake of all Filipinos).

Coral reefs support booming tourist industries in many countries. Catering for snorklers, divers, underwater photographers, sightseers, and fishermen, reef tourism produces thousands of millions of dollars of foreign exchange earnings annually. One reef system alone - Pennekamp State Coral Reef Park (Florida, USA) - attracts 1.5 million visitors per year. More than half of the foreign exchange earnings of the Cayman Islands are from coral reef based tourism. There are now 45 protected coral reef areas (including national parks) in Caribbean countries, but in the absence of broad based ICZM programmes, many have become seriously degraded (ICLARM, 1986).

Coral reefs also serve as natural protective barriers, deterring beach erosion, retarding storm waves, allowing mangroves to prosper, and providing safe landing sites for boats. While Sri Lanka's national ICZM programme is aimed primarily at reducing risks from natural hazards, beach erosion and coastal flooding, a strong component is coral reef protection, necessitating constraints on coral reef mining (Amarasinghe et al., 1983).

Unfortunately, there are numerous destructive forces at work and important coral resources are being degraded at a rapid rate. Some of these forces can be easily controlled through ICZM programmes, but others present serious socio-economic and political problems for many countries. For example, Sri Lanka is faced with finding alternative jobs for thousands of coral miners.

In many countries, reefs are heavily exploited for corals which are harvested for sale as souvenirs or decorations. The market for coral is often quite lucrative and usually export-oriented.

Other damaging activities include the following: 1) siltation and sedimentation created by dredging, filling, and related construction activities and increased soil erosion; 2) pollutants, including spilled oil, industrial wastewater, and domestic sewage; 3) discharge of large volumes of fresh water as may result from diversions and storm-water outfalls; 4) destructive fishing practices, including dynamite; 5) collection of young fishes for sale in the aquarium trade; and 6) tourist visits to reefs which result in breakage from boat anchors and from hand and foot damage.

In addition, there are damages from natural causes such as: 1) outbreaks of reef destroying animals such as crown-of-thorns starfish; 2) diseases like whiteband (which kills elkhorn coral) and blackband (which kills large structural corals); 3) hurricanes that smash the coral and “sandblast” away the living tissue; 4) coral disablement and death from “bleaching” episodes; and 5) die-off or depletion of essential symbionts, such as parrot fish and sea urchins that clean the reef of algae.

Coral reef degradation has serious consequences for tourism, fishing, beach stability and, particularly, for coastal/marine parks. For example, most of the 21 countries and 49 parks (or reserves) in the Caribbean with coral resources have problems (ICLARM, 1986). When serious, coral reef degradation can ruin a park and cut severely into tourism. Some reefs are virtually beyond repair (those closest to settlements) but many that are degraded could still be returned to good or fair condition.

3.1.4 Sandy Beach Systems

Beaches are being lost at a rapid rate through much of the world. No tropical region seems free of risks of erosion. Serious socio-economic situations may arise with erosion and loss of beaches (e.g., risk to property, loss of international tourism revenue). The problem will increase as long as sea level continues to rise - presently from 0.5 to 1 m per century (vertical) in many parts of the world. Beach management is an important element of the ICZM-type programme, and one that should be addressed by experienced professionals.

Beaches are not stable forms; they are dynamic landforms, constantly subject to erosion and/or accretion. The condition of the beach reflects the local balance, or imbalance, between deposition (gain) and erosion (loss). On a worldwide basis, erosion (natural and man- induced) dominates overdeposition, partly because of the global rise in sea level. Consequently, there is serious loss of beach and beachfront in many parts of the world.

It must be remembered that the key to natural protection, provided by the beachfront, is the sand which is held in storage and yielded to storm waves, thereby dissipating the force of their attack. Consequently, taking sand from any part of the beach - dry beach, wet beach, bar or the nearshore submerged zone - can lead to erosion and recession of the beachfront. Therefore, beach conservation should start with the premise that any removal of sand is adverse, whether for construction fill, concrete aggregate, or any other purpose, and should be prohibited.

Ecologically, the beach is a unique environment occupied by animals that have adapted to the constant motion of the sand, gravel or shell. Many important birds, reptiles, and other animals nest and breed on the berm and open beach, as well as feed and rest there. For example, sea turtles (including such endangered species as the loggerhead and green turtle) come ashore during the spring and summer to lay their eggs in the “dry beach” above the high-water line. Also, terns and other seabirds frequently lay their eggs on the upper beach or in the dunes (Clark et al., 1980).

Beaches provide a unique habitat for burrowing species such as mole crabs, coquina clams, razor clams, and others. There may also be a complex intertidal or subtidal community of crustacean organisms that attract shore birds. The shallow waters of the nearshore zone provide habitat for shellfish of many kinds and a wide variety of forage species, which in turn attract fish and birds (Clark et al., 1980).

Beaches protected by coral reefs are often the best place for dwellings and villages in tropical countries. Beaches are also the source of construction sand in many island countries which can lead to catastrophic loss of beach; (e.g., numerous Caribbean island countries have lost important tourist beaches from sand mining). Many countries are now totally prohibiting sand mining. However, sand could be taken from certain beaches if it could be proved that the mining is sustainable (i.e., if there is a strong source of natural replenishment).

Groins, seawalls, and other forms of protection may have negative secondary effects. These structures, intended to stabilize the beach, may actually deflect and reduce supplies of sand to a level no longer capable of replenishing losses caused by storms - the beach may be lost, even while the structure remains. Often the only solution is “beach nourishment”, rebuilding the beach at intervals with sand from elsewhere on land or in the sea. This remedy is so costly that it is not available to most communities.

Since the main threat to the beach is usually from development on the land next to it, beach protection requires coordinated management to include both the beach and the land behind it, including actions to limit construction, require setbacks, prevent excavation, and control beach, harbour, and inlet structures.

The general goal for a management programme should be to maintain the beach by protecting both the natural processes that supply the sand and the sand-storage capacity of the beach. Meeting this goal will require careful examination of conservation needs, natural processes, building practices, and corrective engineering proposals that affect whole beach systems. This process can best be developed through an ICZM programme, as it is in Barbados. Specific guidelines for beach and dune conservation are given by Snedaker and Getter (1985).

3.1.5 Other Habitats

In addition to mangroves, intertidal areas of the coast include salt marshes and open tide flats. Salt marshes, where they exist, serve many of the same ecological purposes as mangrove forests. They assimilate nutrients and convert them to plant tissue which is broken into fine particles and swept into the coastal waters. In addition the marsh provides a special habitat for many valuable species.

Extensive areas of tide flat (mudflats, sand flats, etc.) are often found in estuaries and lagoons. Such flats are important in processing nutrients for the ecosystem and providing feeding areas for fish at high tide or birds at low tide. Mud flats are often important energy storage elements of the estuarine lagoon ecosystem. The mud flat serves to catch the departing nutrients and hold them until the returning tide can sweep them back into the wetlands. In many estuaries and lagoons, tide flats also produce a high yield of shellfish.

At the higher latitudes there are extensive beds of kelp in certain areas, such as southern California and southwest South Africa. Kelp is a brown alga that roots on the bottom of the sea and extends, via a long stalk, to the surface where its fronds spread over the surface of the sea. Kelp often grows in thick stands, creating a submerged forest that provides an important multiple-species habitat from surface to bottom for sea otters and many other valuable species. These kelp stands are vulnerable to over-harvesting (for alginic acid), species imbalance (too many kelp-eating sea urchins), and pollution.

3.1.6 Lagoon and Estuary Systems

The subject here is coastal embayments - semi-enclosed, sheltered, shallow water bodies that have special characteristics and provide essential natural services. These include such water bodies as lagoons, estuaries, small bays, sounds, fjords, esteros, etc. Many such basins have been converted into harbours, or even large commercial ports. It is to be noted that these embayments are not the “enclosed seas” referred to elsewhere in this report which are large, deep water bodies such as the Black Sea and the Mediterranean.

Estuaries (those supplied by fresh water from rivers) exist, in some form, throughout the tropics except in arid/semi-arid regions (where major rivers are few and discharge is sporadic) and on small islands. Lagoons (limited fresh water supply, high salinity) also exist widely - occupying 10 to 15 percent of the world's coastline. Areas of particularly extensive lagoon/estuarine environment include Brazil, West Africa, the Bay of Bengal shores of India and Bangladesh, and the Atlantic and Gulf of Mexico coasts of the USA.

Both estuaries and lagoons maintain exceptionally high levels of biological productivity and play important ecological roles including: 1) “exporting” nutrients and organic materials to outside waters through tidal circulation; 2) providing habitat for a number of commercially or recreationally valuable fish species; and 3) serving the needs of migratory nearshore and oceanic species which require shallow, protected habitats for breeding and/or sanctuary for their young (nursery areas).

Estuary and lagoon ecosystems play a major role in the life cycles of economically important finfish and shellfish species by providing feeding, breeding, and nursery habitat (Clark, 1977; WRI, 1986). For example, over 90 percent of all fish caught in the Gulf of Mexico are reported to be estuarine dependent to some degree.

These coastal water bodies have sustained human settlements dating back to prehistoric periods. In addition to shipping, modern day lagoons and estuaries serve a multitude of purposes including waste disposal, mariculture, recreation, and residential development (Figure 3.3).

Figure 3.3

Figure 3.3 Generic cross-section of a true estuary. Showing that the area of greatest richness occurs between the ocean and the fresh water source where intermediate salinity is found and where small nursery-stage fish and shellfish find optimum survival conditions (richness is measured as gross primary production). Source: Economic and Social Council (1987)

Some large lagoons have been drained and/or filled to create real estate or agricultural land, most notably in land-scarce regions (such as in Japan and in the Netherlands).

The intensive use of embayments that serve as ports and harbours creates a variety of environmental impacts and severe losses of estuarine and lagunal natural resources. Improperly planned development on the shores of estuaries and lagoons creates a variety of short and long term economic losses and opportunity costs resulting from resource collapse. It should be noted that the same management approach may be effective for solving multiple use problems in larger, more open systems like the Bay of Bengal or Gulf of Thailand.

A major source of degradation of shallow embayments is their continued use as pollutant discharge areas. Aside from outright fish kills and other dramatic effects, pollution causes pervasive and continuous degradation, evidenced by the gradual disappearance of fish or shellfish, or a general decline in the natural carrying capacity of the system. The most likely sources of pollution are agricultural and industrial chemicals and organic wastes. Such contaminants in high concentrations create a hostile environment that drives away fish, prevents shellfish from reproducing, or undermines the food chain.

The increased usage of many of these water bodies for transport of oil, chemicals, and other toxic materials - whether by ships, barges, pipelines, or railroads - presents a continuous threat. This pollution is particularly damaging to estuaries and lagoons because their sluggish circulation enables pollutants to reach high concentrations.

Because of the importance of water circulation and flushing in lagoons and estuaries, activities that alter basin configuration can create disturbances with far-reaching effects. Major adverse effects stem from construction of causeways and bridges and from dredging undertaken to create navigation channels, turning basins, harbours and marinas. Other problems arise from laying pipeline or excavating material for fill or construction.

An increasing threat to the well-being of estuaries/lagoons is the impoundment and/or diversion of rivers at upstream locations. When portions of the coastal watershed system are altered or short-circuited, the natural flow pattern is disrupted and estuaries may be subject to surges of fresh water. This not only disturbs the ecosystem, but also increases flood hazards.

The most confined embayments (particularly lagoons) need a maximum of protective controls: protection of wetlands (mangroves, salt marshes) tideflats, and beaches; additional “buffer strips” above wetlands; control of sewage and storm drainage effluents; safeguards against runoff of soils, fertilizers, and biocides from the coastal upland; restrictions on industrial siting; and so forth. The complexity of these problems can best be addressed through an ICZM approach (Figure 3.4).

3.1.7 Critical Habitat Management Issues

While mangrove forests provide life support and income for millions of people, few countries have created effective mangrove conservation programmes. Where laws have been passed, enforcement is often lacking.

The lack of an overall national conservation policy and an ICZM-type programme for the coast weakens the potential for enforcement of laws and regulations. Because mangrove forests are a most important habitat and source of nutrition for fishes, rampant exploitation of the world's remaining 24 million hectares of mangrove forest should be curtailed.

In these situations, the basic habitat and its functions are lost, and that loss is frequently greater than the value of the substituted activity on a long-term basis. In general, these kinds of problems are generated by ignorance of the values of the functioning mangrove system and the absence of integrated planning that takes these functions and values into account.

Figure 3.4

Figure 3.4 Type of Impacts and Stresses That Could be Addressed in an ICZM Regional Programme - Jersey Bay, Saint Thomas, US Virgin Islands. Source: Towle (1985)

Seagrass meadows exemplify that much of the damage to marine habitats is not evident. For example, submerged seagrass meadows are a major marine habitat and ecological component of shallow tropical coastal waters, but most people are not conscious of their existence, much less of their important role. Consequently, they are being depleted by widespread dredge and fill activities and by water pollution, including brine disposal from desalination plants and oil production facilities, waste disposal around industrial facilities, accidental spill of petroleum and petroleum products, and thermal discharges from power plants. The loss of seagrasses - an important habitat and source of nutrition - can cause a significant loss in marine life and fisheries production. Because so much of the damage is unseen, it is often overlooked.

Regarding beaches, it should be clearly understood that problems usually result from human actions. Beach and dune systems in their natural state provide a buffer against storm caused erosion and storm breaching. The natural forces at work are immense; therefore, structural solutions to beach erosion and protection of shoreline property from the hazards of sea storms may be expensive and are often temporary or counterproductive. Normally, if nothing is built either on the beach or next to the beach, it will remain as long as the process of natural replenishment continues. Mobile and responsive, the beach will usually remain over the years, but even if sea level or other natural factors cause erosion, problems will not usually emerge unless there are houses or other structures placed near the beach.

3.2 Ecological Issues and Resources

3.2.1 Non-Sustainable Development

The risk of overexploitation of coastal resources is high with consequences such as biological and economic stress, loss of development opportunities, conflict, and reduced seafood security. Basic resources such as fuel, water and fertile land are in short supply and fish stocks are already heavily exploited in many countries. Resources should not be harvested, extracted or utilized on a non-sustainable basis; i.e., in excess of the amount which can be regenerated over the same period. In essence, the resource is seen as a capital investment with an annual yield; it is therefore the yield that should be utilized and not the capital (Clark, 1991c).

Pursuing development on a sustainable basis is recognized as an absolute necessity to sustain progress in health, food security, housing, energy and other critical needs. This requires maximum efficiency in the use of the resources and in the application of capital investments and recurrent inputs. It calls for the full utilization and valuation of the primary products and by-products it contains. Many countries are finding it necessary to give resource conservation and environmental protection high standing in the economic development planning process (Clark, 1991c).

Natural resource depletion, in all sectors of development, is aggravated by users concerned with short-term profits and by the absence or defined user rights (Clark, 1991c). It must be remembered that the coastal sea and transitional areas are a commons. Theoretically owned by all the people, the coastal commons is held in trust by the government and its uses decided by government. Tenure systems are particularly inadequate in the aquatic coastal area and will require strong efforts to establish them explicitly or revive them formally (traditional user rights).

3.2.2 Pollution

One of the most serious indirect impacts of coastal developments is that of a decline in water quality. Polluted effluents are often the most common source of adverse effects on coastal and marine ecosystems (Table 3. 1). Some of the more common sources of pollution and their impacts are discussed below (Clark, 1991a):

Domestic Sewage: Sewage outfalls (discharge) are troublesome, particularly if inappropriately sited or inadequately treated. Domestic sewage may result in eutrophication by overloading the marine environment with nutrients and may introduce pathogens and toxic matter. The consequences of discharging untreated sewage into the coastal environment includes environmental degradation associated with eutrophication and potential or actual impacts on public health due to sewage mediated pathogens. This is exemplified by the forced closure of a hotel in Costa Rica which was responsible for discharging raw untreated sewage in the nearby Manuel Antonio National Park.

Eutrophication (overfertilization): Caused by excessive nutrients from organic waste (like sewage). In particularly susceptible environments, such as coral reefs, this pollution impact disturbs the delicate balance maintained among a large number of different species, often causing dramatic increases in populations of nuisance species (e.g., algae) at the expense of prized species (e.g., lobster). However, research in Barbados showed that nutrients can be beneficial to coral ecosystems in small amounts but destructive in larger amounts. Other examples of beneficial effects of sewage have been found but techniques for evaluation are not available.

Agricultural Wastes: Agricultural wastes (e.g., manure, fertilizers, pesticides) contribute nutrients in the form of fertilizers as well as toxic compounds from agricultural pesticides. Many of these toxic compounds have a long half-life period, remaining active for many years and as a result penetrate most ecosystems, including even those of “remote areas” such as the Antarctic.

Industrial Wastes: They contain a variety of toxic substances including heavy metals (lead, mercury, cadmium, etc.), radioactive elements, acids and innumerable other toxic industrial chemicals. The most important sources of heavy metals in the tropical marine environment have been cited as the result of mining and dredging operations, smelting processes, offshore oil drilling, desalination plant effluents, thermal power plant, effluent and sewage discharge.
Table 3.1 Typical Coastal Water Pollutants and Their EffectsSource: Division of Coastal Management (1986)

Petroleum HydrocarbonsFuel exhausts Motor oil and grease Power plant emissions Industrial discharges Spills and dumping Leaking underground storage containers Urban runoffSpills can kill aquatic life, damage beaches, and permanently destroy wetlands.
Runoff can be toxic to marine organisms - causing death, disease and reproductive problems.
Chlorine Water treatment plants Swimming pool backwashKills aquatic life.
NutrientsAgricultural, forestry, and urban runoff Industrial and boat discharges Sewage treatment and package plants Septic tanks Animal feedlotsEnrichment of rivers and sounds (eutrophication) resulting in algae blooms. Blooms can alter the food chain then decay, depleting oxygen and causing fish kills. Eutrophication is also suspected of causing some fish disease problems.
Fresh WaterWater running off impervious surfaces Land clearing Draining wetlands Channelization of streamsChanges salinity patterns in estuarine habitats, causing slowed growth or death of juvenile organisms, or poor reproduction.
Bacteria and VirusesSeptic tanks that are spaced too densely, placed on porous soils, located in high water tables, or that leak
Sewage treatment or package plants Boat discharges
Animal feedlots
Urban runoff
Contaminates shellfish waters, so consumption of shellfish may cause disease.
Contaminate groundwater, so using for drinking or bathing may cause disease.
Contaminates surface waters, so swimming may cause disease or wound infections.
SedimentLand clearing
Clogs marine waters.
Covers marine habitats, smothering some organisms.
Causes turbidity in water, shading out producer organisms and altering the food chain.
Electric generating plants
Urban runoff
Alters reproduction of fish.
Reduces dissolved oxygen which may then cause fish kills.
Contaminates fresh water supplies used for drinking, irrigation, and the like.
Heavy MetalsFuel and exhaust of motorboats and automobiles Industrial emmissions and effluent Sewage treatment plant effluent
Landfill wastes/leachate
Urban runoff
Naturally in soil
Hazardous waste spills and disposal
Accumulate in fish tissues and are passed on to humans.
Contaminate drinking water, causing brain damage, birth defects, mis-carriages, and infant deaths.
Synthetic Organic ChemicalsForestry, urban, and agricultural runoff Industrial and municipal effluent Spills or dumpingCause cancer, birth defects, and chronic illness when consumed in contaminated water supplies or seafood.
Oil Spills: Accidental spills are becoming increasingly more common as sea traffic increases, facilities are built and the dependence on fossil fuel grows. In small island ecosystems, the impacts can be felt even more as important habitats are much smaller in scale and as such may have an increased vulnerability. Again the presence of dissolved fractions may have far-reaching consequences, but much work needs to be done in this area.

3.2.3 Threats to Biological Diversity

The global threats facing species and their habitats (biodiversity) include land use changes, overexploitation of resources, conversion of natural areas, pollution and effects of climate change. A large proportion of world population growth will take place in coastal zones of developing countries and will be accompanied by rapid urban development and changes in land and resource use. Increasing urbanization, industrial development, agricultural intensification and expansion of tourism will all have profound effects on natural habitats and species.

Urban sprawl has already proven to adversely affect biodiversity. Currently, about 50 percent of the world's urban waste-water is directly discharged into sea or other water bodies close to the sea without any kind of treatment - contributing to aquatic eutrophication and disruption of ecosystems. With intensifying demographic pressures, the sheer volume of waste products is likely to increase.

Gaseous and liquid industrial emissions and solid wastes also threaten to have an increasing impact on the environment. Expanded road networks, new dams, industrial complexes and enhanced infrastructure are likely to further stress ecosystems and reduce species diversity.

Expected increases in cultivated areas will have a significant impact on natural areas. Increases in demand for water for irrigated areas will change patterns of water flow, further altering ecosystems. Irrigation management will be vital to ensure adequate water supplies, reduce pollution from agricultural inputs and control soil salinization. Intensification of agriculture implies increased use of chemical inputs, which, without careful control, affect water quality, contribute towards the eutrophication of river and coastal marine areas, enter into food chains, and debilitate ecosystems (Clark, 1991c). Therefore, if wild species are to survive and prosper, some kind of integrated farm management should be tried (Holl et al., 1990).

Mangrove forest mismanagement and overuse are also issues of global importance. Overexploitation of forests for lumber, grazing and fuelwood needs is a common practice. Deforestation not only leads to the loss of a valuable resource, but also reduces watershed protection, increases surface water runoff, increases soil erosion and desertification, contributes to the siltation of dams, and results in the further loss of an already decimated habitat (Clark, 1991c).

The degradation of both terrestrial and marine ecosystems through over-exploitation and misuse of resources by mankind could lead to further reduction in crucial global ecosystems. Amongst the measures that could contribute to the protection of these ecosystems against these impacts are various types of marine and coastal parks and reserves, managed according to carrying capacity principles (Clark, 1991b).

3.2.4 Natural Effects

Conservation considerations are often compounded by natural disasters or other naturally occurring phenomena that impact on environmentally sensitive areas. For example, the recent spate of hurricane destruction to Caribbean coral reefs has made it difficult to assess development because the reefs are so badly broken up (Clark, 1991).

Tragedy is often brought by natural outbreaks of disease, like the one which caused massive die-off of the long-spined sea urchin throughout the Caribbean in the early 1980s. Other outbreaks such as black band disease, coral bleaching, etc., are also causes for increased concern.

Coupled with these are the feared global temperature rise which could (or already might) be altering balances in systems which may not recover from such stress, and which is probably the result of a mix of natural and human causes. Global climate change (whether natural or human-induced) will affect coastal zones. They will be impacted by sea-level rise (“greenhouse effect”), changes in ocean coastal processes, modifications of river runoff patterns and sedimentation and from the expected increase in floods, storms and hurricanes. Consequences for coastal settlements are still difficult to forecast with any accuracy but could be significant (Clark, 1991b).

One of the South Pacific's worst biological disasters is the widespread invasion of coral reef systems by Acanthaster planci (crown-of-thorns starfish) which have devasted large parts of the Great Barrier Reef (Australia) and of other reef tracts.

3.2.5 Fisheries

A major global problem is the widespread depletion of seafood resources caused by coastal pollution and critical habitat destruction along with overfishing. Lester R. Brown (1985) gives the following account of world fisheries: “Their annual harvest … exceeds world beef production by a substantial margin… fisheries supply 23 percent of all animal protein consumed… In many low-income countries, as well as in a few industrial ones, fish are the principal source of animal protein…millions of people make their living from supplying fish…”

In a time of rapid increase in the global need for protein, it is necessary to conserve the productivity of coastal habitats for fisheries production (the supply), as range lands are protected for livestock, farmlands for crops, and forest lands for wood. This can be effectively managed through an ICZM programme which can help prevent pollution, regulate harmful development, and create protected areas. This should be coupled with control of destructive fishing methods.

An example of coastal resources trouble brewing is the Philippines, where according to a recent study (Maclean and Dixon, 1984): “Per capita fish consumption decreased 47 percent from 1970 to 1980…prices seem to be moving upward…many believe a nutritional crisis of serious proportions is emerging.” The World Resources Institute warns: “The outlook for marine fisheries is not bright. The factors that have caused recent problems - limited resources and excessive exploitation - are likely to continue.”

3.2.6 Ecosystem Level Conservation

The complexity of biotic systems and the interrelatedness of their components require that each coastal water ecosystem be managed as a whole system. Neither piecemeal management nor major treatment of single components or single species will fully succeed. Furthermore, the major external sources of influence on coastal water systems must be considered - shoreland watersheds, shoreline areas, and offshore waters are all linked to the coastal system. Therefore, the ecosystem defined must embrace a complete and integral unit, one that includes a coastal water basin or basins, and the adjacent shorelands to the extent that they have significant influence on coastal waters.

Also, the management programme must look to, and protect, the important ecological processes - the underlying factors which explain the high production levels of coastal seas, such as: 1) the key role of fresh and marine waters in providing and renewing nutrients, organic material, and oxygen; 2) solar radiation which is maximized as an energy source because of the characteristic shallow depths of these areas; and 3) the high mixing rates which assist gas exchange, nutrient circulation and waste removal.

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