Until quite recently, man's impact on marine ecosystems has been considered as largely restricted to the effects of fishing. The capacity of the marine environment and living resources to absorb the effects of other human activities has been considered effectively unlimited. To a certain extent, this has been due to the difficulties of documenting effects in an opaque medium. It seems that, as for terrestrial and inland aquatic ecosystems, some marine ecosystems have shown resistance to ecological impacts, whereas others are particularly sensitive.
Before considering how the concept of sustainable development applies to living marine resources, it is important to recognize that “development” (not necessarily sustainable) affects resources in two main ways:
In the broadest sense, all harvesting of living organisms, whether whaling, the mining of coral reefs for structural materials, or the cutting of marine algae, can be considered as “fisheries”, and this term encompasses harvesting of living organisms for food or for other purposes, from estuaries and intertidal regions to the high seas. Fishery development therefore encompasses the impacts of harvesting on all components of the marine food web.
Changes in environmental conditions as a result of other human activities falling under the heading of “development” in the classical sense also affect living resources, which are also best considered under two main headings:
those activities taking place within, or directly adjacent to, the marine environment, such as coastal development, shipping, at-sea dumping, coastal tourism, undersea mining, and gas and oil extraction;
those outputs from human activities inland that affect MCB's via riverine transport (e.g., transport of products of land erosion, nutrients, pesticides, metals and other toxic materials), or via atmospheric transport of materials (e.g., organochlorines, some heavy metals: see e.g. Ackefors et al., 1990).
Various definitions of marine pollution need to be taken into consideration in discussing various man-induced effects on marine resources. Several have been proposed;
GESAMP (1983) defined pollution as:
“the introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities including fishing, impairment of quality for use of sea water, and reduction of amenities.”
The UN Convention on the Law of the Sea, in 1982, in Article 1, paragraph 1(4), largely followed the GESAMP definition, by describing marine pollution as:
“…the introduction by man, directly or indirectly, of substances or energy into the marine environment, including estuaries, which results or is likely to result in such deleterious effects as harm to living resources and marine life, hazards to human health, hindrance to marine activities, including fishing and other legitimate uses of the sea, impairment of quality for use of sea water and reduction of amenities;”.
Under Article 1 of the London Dumping Convention, contracting parties pledge to:
“take all practicable steps to prevent the pollution of the sea by the dumping of waste and other matter that is liable to create hazards to human health, to harm living resources and marine life, to damage amenities or to interfere with other legitimate uses of the sea”.
The GESAMP definition has been used in all internationally agreed legal instruments for the prevention and control of marine pollution. It has been mentioned that the introduction of the same substances into the marine environment that do not cause the above-mentioned negative effects would not be considered pollution. Thus, if hypothetically, it were decided to introduce nutrients into a coastal lagoon to increase fish yield (a documented effect of moderate levels of “pollution” by biodegradable organics or nutrient salts, which has also been referred to as “enrichment”), this would not be considered as pollution under the GESAMP definition.
Chemical pollution may influence fish production in numerous ways: reduction of stocks by mass mortalities; gradual decline, or changes in composition, of populations or entire ecosystems; increased occurrence of diseases; deterioration of fish-food quality; lowered growth rates. The seas, and land-locked water bodies, receive a significant proportion of pollutant chemicals via the atmosphere, so that effects distant from the source cannot be discounted. Despite this, although such effects need much more rigorous control, there will be great pressure for some use of the marine environment for waste disposal, as a consequence of expected world population growth to some 7 billion people by the beginning of the next century. It would be more practical to attempt to define the levels of pollution that cause no appreciable risk and the areas where such risk is most serious for living resources.
GESAMP (1986) has defined the ability of a component of the marine environment to accommodate a particular level or intensity of human activity as its environmental capacity, a concept that is analogous to the benchmarks discussed in section 4.1, above, in relation to fishing intensity. Intrinsic to this concept is the recognition that:
the environment has a finite capacity to accommodate wastes without becoming significantly altered by them;
such a capacity can be quantified.
a certain level of contaminant will not produce an unacceptable impact on the living marine resources;
The impact of the disposal of waste materials at sea, either deliberately or inadvertently, on living marine resources, depends to a significant extent on the location as well as intensity of disposal. Thus, an oil spill in open-ocean waters can be expected to have less serious (though not necessarily negligible) effects than in nearshore Arctic waters. As noted earlier, if disposed of in a responsible manner, moderate levels of waste may in fact enhance the productivity of ecosystems. In many marine environments, diversity and productivity are limited by the relative uniformity of the bottom topography. In cases such as some flat bottom areas, the dumping of materials meeting specified criteria in agreed zones to form artificial reefs might be in contravention of the London Dumping Convention (IMO), but could be considered desirable for the development of coastal resources or to protect sensitive marine habitats from trawling. Thus, there is a need for discussion of exactly what type of dumping, where, and at what intensity, should be considered harmful, and whether existing conventions need modification under certain circumstances in order to promote sustainable development.
Consumers are becoming increasingly aware of the quality of fish products and of the more stringent regulations being introduced by governments to ensure such quality, which make it more difficult for developing countries to meet minimal standards set out under the FAO-WHO Codex Alimentarius (FAO/WHO, 1993). Discharge into the environment, and subsequent concentration in the food web of such contaminants as heavy metals, PCBs and dioxins, can have an impact on fish-product quality. The problems of contamination of the inland and coastal environments and, consequently, of aquatic products by pathogenic bacteria and viruses contained in water contaminated with sewage, and in uncontrolled domestic runoff from urban areas, are growing worldwide (Ahmed, 1991). Nutrients from the same sources also encourage blooms of toxic dinoflagellates and red tides that may contaminate fish and shellfish, whether wild or cultured; this type of contamination is paralled in some tropical areas by the increasing prevalence of ciguatera (Pulos, 1986). Other forms of fish toxicity and algal blooms induce fish kills in the tropics (White et. al., 1984). In areas of oil exploitation, catches and fishing gears may have to be discarded because of tainting.
Since human populations tend to prefer living near or at the coast, and coastal human populations are still growing in many countries, construction has increased accordingly, in the form of human residences and hotels, ports, marinas, and the associated infrastructure (sewage treatment plants and rubbish dumps, shops, banks, post offices, hospitals, and so on), as well as industrial installations (see section 5.3, below). Not only does human settlement bring with it the problems of contamination referred to elsewhere in this chapter, but it also threatens the habitat of many species of marine life: fish, turtles, birds, mammals and other organisms that habitually live in the coastal zone, in the sea or on the land nearby. Uncontrolled cutting of mangroves, whether to facilitate coastal construction for shrimp ponds, or to use mangrove wood (e.g. Soepadmo et al., 1984; UNDP/ Unesco, 1987), may, in excess, also be examples of environmental degrdation that have adverse effects on coastal marine resources.
Perhaps coastal construction itself does not directly affect the fishers (who stand to benefit, at least initially, from the correspondingly increased demand for their catches from the increased human population), but alters the sedimentation pattern and ecological characteristics in the coastal zone. Coastal construction significantly impacts the local marine ecosystems and often forces fishers to change their gear/methods and target species. The traditional practice, in some countries, of landing fish directly on the beach and selling the catch directly to the public (and to the seaside restaurants) may no longer be feasible; fishermen may be forced to go farther to reach the nearest fishing port. This may, for example, force an “improvement” in mechanization of the fishing boats and in the marketing of the fish, but often leads to higher costs. Thus, coastal construction may improve the capacity of of these critical habitats by indiscriminate trawling, by landseaside resorts to receive visitors or new residents while making it harder to feed them, as far as the sea-food component of their diet is concerned.
Industries are established in coastal zones mainly because of the need for a place (the sea) to dump waste, or the use of the sea as a source of cooling water (i.e., to dump heat). Most industries also have to dispose of chemical waste from manufacturing processes (e.g., mercury compounds/fungicides from paper-pulp production), and sometimes physical waste such as sludges (e.g., from the processing of aluminium or titanium oxide ores). Desalination plants, by definition, are sited at the coast; and besides heat, they may discharge hot brines.
Not only can coastal industries degrade the local marine environment where they discharge, but they also occupy the terrestrial environment in their vicinity at the expense of other biologically important critical habitats for marine and coastal species. To the extent that disruption and contamination depress the quality and abundance of the marine fauna, local fisheries are adversely affected by coastal industry; and, in the long term, the sum of all coastal industrial discharges not fully absorbed by the sea has the potential to adversely affect coastal marine fisheries in general. However, it is not always the case that fishes (of economic, fishery interest) are adversely affected by some forms of chemical pollution. Nevertheless, on the whole, coastal industry (even including industrial-scale fish farming) has the potential to be prejudicial to coastal fishery interests, and needs reconciling with fisheries in the ICAM context.
Marine mining includes drilling for oil and gas and dredging of gravel and sand. It may also include the breaking up of coral reefs and the removal of manganese nodules from the ocean floor (Salvat, 1987). Not so well known is the dredging of the sea bed to obtain minerals containing tin, gold, diamonds, ilmenite, rutile, zircon or monazite, for example. The mining of deep-sea manganese nodules (which also contain several other metals, such as cobalt, nickel, iron etc.), will not be a commercial undertaking as long as these metals are found more cheaply on land. When such mining becomes widespread, and especially if some of the industrial processing is done at sea, the consequences for fisheries may become important (discharge of waste rock dust into the sea to create singinficantly increased turbidity or increased concentrations of elements that are normally rare in sea water but become toxic at higher concentrations, for example). As noted, most sea-bed mining is more costly than land mining, so that this particular intervention is at a relatively early stage of development.
At present, the extraction of oil and gas, for energy and for chemical transformation, is an important marine activity in some regions. Once the exploratory drilling phase is over, and the production platforms are in place, fishing is only likely to be seriously affected if these platforms are closely spaced, so that a substantial area of sea bed is closed to fishing; however, such “platform parks” may provide a “refugium” for fish and an opportunity for sports angling (e.g. Dugas et al., 1979) stock (Reggio, 1987). Platform accidents, leading to discharge of substantial quantities of oil into the sea, are more likely to have adverse effects on other human activities such as tourism than on fishing where more serious adverse long-term effects may stem from toxic waste dumping.
Gravel, sand and fossil coral beds are mined in some areas mainly to provide civil construction materials. In countries where building materials are in short supply or expensive, coastal se-bed dredging for gravel and sand is often an important marine activity (ICES, 1992a; Campbell, 1993) whose interactions with fisheries are still not well defined. Such extraction adversely affects benthic organisms by destroying habitats and damaging spawning grounds of demersal and other fishes; it also interferes with trawling and other bottom-fishing methods; however, the duration of the effects, once this form of mining has ceased may be relatively short for most smooth bottom habitats. It should be noted that coral reefs have three major ecological functions which are usually seriously compromised by mining: to enclose a coastal lagoon (i.e., create a natural fish pond); to protect the coast (therefore, fish habitat) from coastal waves and storm surges; and to provide a region of attraction for species of fishery interest.
The recreation of citizens and tourists is a major economic activity in many countries, whether rich or poor. With respect to the coastal zone, wherever clean beaches, sunlight and all the attendant local infrastructure (hotels, places of entertainment, sanitary installations, banks, post offices, shops, etc.) can be found, human beings who can afford to go there, will pay money to do so. In some places, such as along the Mediterranean littoral, a resort's resident population will be multiplied several (3-5) times during the holiday season. (Estimates of several tourists per linear metre of Mediterranean coastline per year have been quoted). This requires significant investment in sanitation services, accommodation (hotels) and other facilities for the maximum number of residents, even though these facilities will be under-used for perhaps half the year. If the authorities do not provide facilities or services, especially to deal with the increased waste, the coastal sea is relied upon to handle that which cannot be treated. While the sea's capacity to do so may be considerable, it may depend quite heavily on the rate at which the local sea is changed (flushed) by local currents. Untreated waste discharge also leads to increased litter in the sea and on the sea bed, and to higher than usual incidence of potentially dangerous micro-organisms.
The idea of dedicating some parts of the coastline to tourist activity and others to fishing and/or mariculture (i.e., applying the ICAM concept) does not appear to have been widely incorporated into the public policies of most countries, even if there has been some de facto geographical separation of human activities, (usually to the disadvantage of fishermen) in the course of development.
This subject was taken up in section 2.1.3 under fisheries of the nearshore area. Its impact on traditional capture fisheries is the subject of the present section.
Coastal marine aquaculture may provide a solution to shortage of high-priced species in high demand, which cannot be supplied by fishing. Most such activities are still carried out in coastal lagoons and small, well protected bays. The culture of species of interest (shrimps, sea bream, salmon, for example) is sometimes based on natural stock entrapped in a lagoon or bay and then fed in enclosures until commercial size. Only in certain cases are species raised throughout their whole life cycle (artificial fertilization, culture of the larvae, then reared to commercial size (e.g. Shokita et.al., 1991).
To “force feed” cultured species by the addition of food to the natural environment may, in certain circumstances, lead to abnormal discharge of wastes to the local coastal sea, leading to local eutrophication (Enell and Ackefors, 1991), perhaps causing harmful plankton blooms (e.g. White et. al. 1984). GESAMP (1991), has considered ways of reducing the environmental impacts of intensive coastal aquaculture.
Marine aquaculture development may not be viewed favourably by all fishers because of the competition for markets that the cultured species may engender. To avoid future problems as marine aquaculture develops, it is desirable to ensure, where possible, that unemployed or surplus fishers find some role in this sector, as in other coastal sources of employment.
Busy commercial shipping routes are not easily compatible with commercial fishing. Apart from the risk of oil spills, oil tankers, besides being generally very large and not easily manoeurable near shore, may wash out their oil tanks (albeit illegally) thus giving rise to a form of oil pollution that may be unfavourable to fishers (degradation of the marine environment, tainting of fish flesh, oiling of fishing gear, especially nets, etc.). Major oil spills may be local catastrophes from the fishery standpoint but, on the whole, the risks of oil and gas transport have perhaps been rather exaggerated with respect to less spectacular forms of pollution discussed in other sections of this report.
Inappropriate agricultural practices in the hinterland of the coast have the potential to pose a serious problem to coastal fishermen both with respect to pesticide and fertilizer loss.
Pesticides, which may be over-applied, can be washed by rain from the cultivated land surface directly into the sea, or indirectly via rivers debouching into the sea, with potentially adverse affects on the coastal marine fauna and species of fishery interest. There is also a substantial transport of agricultural pesticides by the atmosphere (Goldberg, 1976); they may reach the sea, but over a wide area (regional, if not global) so that although the effects on the coastal sea are not easily quantifiable, distant ecosystems, such as those in the Antarctic, may accumulate detectable levels of industrial chemicals.
The effect of fertilizers washed or discharged via rivers into the sea has been discussed in section 2.1.4; the possible effects on coastal fish stocks, hence on fisheries, are potentially very important, often adversely in the vicinity of point sources, perhaps more positively farther away after dispersion has taken place. Some of the problems of the effects of agricultural fertilizers, with particular reference to nitrogen, have been discussed by Clarholm et al. (1988), and also at the 1991 FAO/Netherlands Conference on Agriculture and the Environment (FAO, 1991b).
The number of species foreign to a particular marine environment that have either been deliberately or accidentally introduced by man has increased considerably, and it is clear that changes in the environment due to human activities may facilitate this process. The establishment of exotic species has often resulted in far-reaching changes to the faunal composition of many of the world's enclosed and semi-enclosed seas, estuaries and coastal marine waters (Li and Moyle, 1981; Carlton, 1989). The effects of such introductions include: immediate ecological impacts at the community level through changes in inter-specific competition and predation; changes in the nature of the environment itself through the influence of certain organisms, and possible genetic degradation of indigenous stocks. FAO has collaborated with ICES in the preparation of a “Codes of practice and manual of procedures for consideration of introduction and transfers of marine and freshwater organisms” (Turner, 1988). The co-introduction of pathogenic organisms has often adversely affected native and introduced species alike, particularly cultured shellfish (Chew, K.K. (1990)).
The conservation of biodiversity and genetic diversity of aquatic organisms (e.g. Norse, 1993; FAO, 1992d, 1993i, Grassle et al., 1990) poses problems at two main levels: firstly, for wild fish stocks, the loss of species and, more especially, local races, through environmental change, overfishing or competition through species introduction. The trend towards developing new, uniform strains adapted to rearing in captivity is increasing the dangers these traits pose to wild populations as a result of the escape of cage-cultured strains, and consequent cross-breeding, e.g. between cultured and wild salmon strains (FAO, 1993i). Such genetic “accidents” could reduce the variability native stocks need to ensure resilience and adaptability in a changing environment (Smith, 1994).
One possible effect of intensive fishing on biodiversity is gear selection for specific fish sizes, depending on the fishing method. Such pressures may also lead to selection for early-maturing or slow-growing individuals, with effects that are expected to be measurable over a limited number of generations (Smith, 1994). This type of effect may be reduced or reversed by alternative fishing strategies.
One special biodiversity problem related to the influence of man-made canals linking faunistically different regions, and the influence of shipping in facilitating inadvertent transport of exotic species (e.g. Carlton and Geller, 1993). This type of species introduction could be greatly facilitated by a sea-level canal such as the one under consideration to link the Atlantic and Pacific Oceans across the isthmus of Panama (Ambler, 1987). The migration of some 500 Indo-Pacific species into the eastern Mediterranean since the construction of the Suez canal is a specific example of such effects (Por, 1968). This, and their subsequent spread westwards and northwards, was also facilitated by the more saline conditions created by construction of the Aswan Dam and consequent removal of the low-salinity barrier created for Red Sea immigrants by the Nile discharge into the eastern Mediterranean Sea. The dramatic changes in the Black Sea fauna due to the introduction of exotics better adapted to eutrophic conditions than the native fauna is another example (Ivanov and Beverton 1985; Caddy and Griffiths, 1990; GESAMP, 1995).
The conservation of biodiversity of aquatic organisms attempts to counteract loss of species and local races, due to harmful practices such as overfishing, habitat destruction and pollution. Although relatively few species extinctions have resulted from overfishing, this is not true for for some populations and races, and other impacts of human activities have been critical through their effects on species habitats. The Convention on International Trade in Exotic Species (CITES) is an important mechanism for protecting commercially valuable species which may be subject to international trade.
In general, the conclusion emerges that, as for terrestrial ecosystems, man's intensive exploitation of all habitats and ecosystems reduces their complexity and favours simple ecosystems and pioneering species of generalists, specialized for rapid growth and reproduction, but not necessarily of commercial value.
Some of the variations in the conditions under which marine ecosystems exist, now, and in the future, are likely to be due to global climate change (e.g. Francis, 1990). Such changes will add to the natural variations all ecosystems have always been subject to (see section 3). Their effects on fisheries and aquaculture are, at best, difficult to forecast, although in the case of ‘wild’ fisheries, the key role of environmental change on the year class strength has been recognized as a significant cause of wide changes in strength of recruited year classes (e.g. Fogarty et al., 1991).
The UNEP-WMO Intergovernmental Panel on Climate Change (IPCC) has assembled the views of the international scientific community on the magnitudes of expected global change related to the climate (IPCC, 1992), and international Council of Scientific Unions (ICSU) has initiated an International Geosphere-Biosphere Programme (IGBP) to assess the pace of all the major observable terrestrial changes (Williamson, 1992). Regarding the oceans, the IOC has initiated a Global Ocean Observing System (GOOS) (Kullenberg, Andersen and Cole, 1993).
Preparatory studies suggest that carbon dioxide (a “greenhouse” gas) in the atmosphere, is likely to double by 2025–2050 on a “business as usual” basis, leading to a probable increase in the global mean temperature of 1.5°-4.5°C (IPCC, op. cit.). This may cause a rise in mean sea level of about 20 cm by 2030, and of about 65 cm by 2100, and to an increase in sea-surface temperature of between 0.2°C and 2.5°C. Bakun (1992) projects some likely effects of such changes on coastal and shelf-sea ecosystems, referring particularly to the likely increase in the temperature differences between the land and the sea in the coastal zone, which is predicted to amplify upwelling by changing the coastal air-pressure/wind regime.
The global climate changes mentioned above are not expected to have an adverse effect on fish production, as on terrestrial, lacustrine and riverine ecosystems, although particular stocks may be adversely affected and changes in rainfall and river run-off will particularly affect life in semi-enclosed seas and coastal nursery areas. Coastal aquaculture will also be affected. Tropical upwelling zones, which produce large amounts of fish resources, may shift polewards and increase in intensity. The year-to-year variability of the resources they support may increase; however, increased phytoplankton productivity may reduce oxygen levels and lead locally to anoxic situations. Coral reefs may, as in the past, respond to and reflect changes in sea level, but only if these changes occur in a gradual fashion.
The main uses of the coastal area have been mentioned above; they are, beside fishing: waste discharge (pollution); construction of human habitations and related infrastructure; industrial waste discharge and plant cooling; marine mining; tourism and recreation, mariculture and shipping. Sometimes specific areas in the coastal zone may be reserved for military use. As has been suggested in section 5.8, agriculture in the hinterland, although not a “use” of the coastal zone, could have a significant impact environmentally, by way of release of pesticides and fertilizers (an impact which is not always taken into account in cost benefit analysis of agricultural operations).
It is not usual, or perhaps even possible, for all these uses to all co-exist in the same coastal area. Coastal habitation, tourism and recreation, on the one hand, and industry and marine mining, on the other, tend to be mutually exclusive; and all these uses tend to prejudice the pursuit of fishing (perhaps even sport fishing) and marine aquaculture. The application of an ICAM scheme is therefore important, mainly because ecological criteria of choice in terms of space and objectives are unlikely to correspond to political criteria, or criteria expessed in terms of jurisdiction and economics (Clark, 1992): hence the need to search for a working relationship between ICAM and sustainable development.
The objectives of ICAM in a given place, time and socio-economic context are multiple and often conflicting; thus, as for fishery development itself, these objectives must be clear-cut and related to the political, ecological and socio-economic objectives of the responsible government and local authorities in such a way as to maximize the common good. The public perception of this good may not be constant, but it must also be related to the time scale on which human societal development proceeds: that is, decadal. This common good must, in the current climate of social thinking, have sustainable development as its main objective and as defined at the UN Conference on Environment and Development. Burbridge and Burbridge (MS., 1992), Fallon Scura (MS., 1993a) have reviewed the experiences of UNEP, IUCN and WWF in the implementation of integrated coastal management projects.
Regarding fisheries, most of the world fish catch comes from the coastal waters, not only because the positive effects of terrestrial run-off and the physical interaction between the land and the sea have favoured the productivity of coastal waters, but also because here the resources are closest to where a majority of fishermen and consumers live. However, the multiple uses already referred to make the application of fishery management measures in isolation of doubtful efficacy; the appropriate context could properly be referred to as Integrated Coastal Fishery Management (ICFM): implying that other human activities are evluated as suitable or otherwise depending on their impact on fisheries. The common property idea hitherto predominant in the exploitation of coastal resources has also been largely responsible for the reduction of the resources to levels that no longer sustain the coastal community or even the fishing community itself, in some cases. These two communities (the latter being a subset of the former) have nothing to lose by supporting an effective Integrated Coastal Fisheries Management scheme.
The reduction of user conflict would generally demand the assignation of a value (expressed as some form of rent for use) to a particular area of the coastal zone which would require a restriction on access (either through the economic cost of the rent or through socially established limits), and necessitate zonation (whereby different uses are kept physically separate, so as to avoid adverse impacts on other users and uses, and perhaps above all, on the environment and the natural resources). Among the measures which fall within coastal zonation, are closed areas or marine parks which ensure that a proportion of the coastal ecosystem is protected from resource exploitation (e.g. Agardy, 1994).
