The agro-ecocomplexes of traditional villages in the Dry Zone of Sri Lanka included four major components, namely crop cultivation, animal husbandry, fishery, and forestry. While these four components collectively provided practically all the food and other needs of the village inhabitants, the ecological interactions between these components contributed to the sustainability of the village agro-ecocomplex. Thus the livestock were used to provide draught power for farming, and were fed on crop residues and straw, their dung being used to fertilize the soil. Fishery was mainly on irrigated paddy fields and in the irrigation system, while the fish on the paddy fields consumed harmful insects and worms, and provided fertilizer in their excreta. The village forest on the catchment area, and the trees sparsely grown on the cultivated area and in the irrigation system, substantially contributed to maintain the natural productivity, yielding firewood, timber, and various foods. In this manner, the village agro-ecocomplex functioned to satisfy the needs of its human inhabitants without impairing its own sustainability.

This village agro-ecocomplex system is now in the process of disintegration owing to structural, technological, and institutional, changes brought about by modem development. The reason is that these modern development strategies were basically designed to raise the production of the land-area rather than to preserve the productivity of the given agro-ecocomplex. For while farm mechanization displaced the draught animals, the increased population pressure of more and more humans reduced the grazing lands. Both modern development and population pressure had destructive effects on the forest cover, while increased utilization of agrochemicals adversely affected the fish culture on paddy fields. In this way, livestock, fishery, and forestry, all became insignificant or at least insufficient, and were de-linked from crop cultivation. In consequence, the village agro-ecocomplex has become de-stabilized, and dependence on external inputs has increased so greatly that self-sustainability of the village agro-ecocomplex has ceased to exist except in some remote areas.

A predicted rejuvenation of the Lake Chad fisheries in central Africa, associated with the passing of severe drought conditions in its Sahel environs, is likely to increase significantly the pressure placed on other local resources. In the case of the tree resources, it can be demonstrated that the concentration of population and fish-processing activity along the western lakeshore, will further exacerbate the existing local deficit between demand and supply, leading to increased tree-loss with ultimately devastating results culminating in desertification.

The problem is outlined and discussed in the context of both local and national economic considerations. Particular attention is given to the relationship between increasing demand for fish products in Nigeria as a whole, associated with expansion of population and rapid urbanization, and the commercialization of fisheries production in the Chad Basin leading to much-increased fuel-wood usage. It is clear that Government must play an active, much-expanded role in regulating this situation if severe resource depletion and environmental degradation is not to occur in the foreseeable future.

Non-use existence values are now widely considered to be an important justification for conservation in developed countries. Using the same approach to promote conservation in less-developed and developing countries, with their normally severe economic and social problems, is often wholly inappropriate, as existence values in less-developed and developing countries are usually very small. Conservation on grounds of ethics and aesthetics is a luxury which many of those latter countries do not feel able to afford, or often genuinely cannot.

The establishment of the Ichkeul National Park in northern Tunisia was based primarily on non-use, existence values, but the survival of its wetlands is now threatened by a programme of dam construction. However, the Lake and marshes of Ichkeul have a number of important values and functions. These include livestock grazing on the marshes, the Lake's fisheries, the existing and potential value of the Park as a tourist resource, the role of the rivers in water-table recharge, and the function of the marshes in the ‘free’ treatment of sewage and purification of water. It can be shown that the economic gains from taking measures to prevent degradation of the wetland, namely by releases of water from the dams to maintain the marshes, would outweigh the economic benefits from the use of water in agricultural irrigation, and effectively maintain much of the international significance of the National Park and its surroundings.

It is suggested that promotion of conservation in lessdeveloped countries is likely to meet with much greater success if economic arguments, based on a site's usevalues, are given priority in the approach of conservation organizations from developed countries. The significance of non-use values to nationals of the less-developed and many developing countries is still very minor, although, as their living standards improve, such prospects are likely to improve also. In many instances at least, by raising due awareness of the economic use-values of natural systems, it will be possible to provide a good case for a site's conservation.

Possible solutions to the commons problem have rarely been investigated systematically by the use of biological data on the status and sustainability of the resource. The edible White-spined Sea-urchin (Tripneustes ventricosus) resource of St Lucia, West Indies, is highly prized and vulnerable to exploitation, as is indicated by recent declines in its stocks. In the south-east of St Lucia the resource was almost entirely depleted in an area in which access was free and open. It was not depleted in the other two areas in which there were access controls. In one case, the area was under government control as a marine reserve; in the other, there was a locally practised ‘closed season’ and community-based management of access into a bay.

The results of our study indicated that both government controls and informal, community-level controls can lead to successful resource-management outcomes. These findings challenge the ‘conventional wisdom’ that commonly-owned resources are destined to be overexploited.

The growing interest in environmental impacts of agriculture calls for effective agricultural policies to confront the expanding use of chemical fertilizers. Environmental policies in agriculture should be based on evidence concerning the factors influencing fertilizer usage.

A hierarchical loglinear analysis of some social and economic factors showed that age, education, farm size, and employment status, all exert an independent effect on fertilizer usage. In addition, age and education exert a joint effect on fertilizer usage. It is found that the categories most likely to use high rates of application of fertilizer, at least in Greece, are full-time farmers 56 to 65 years old, well-educated or with small-sized holdings.

The EEC's socio-structural policy for agriculture is examined in the light of the above findings. It is concluded that the policy could form the core for an effective environmental policy in agriculture. However, areas are pointed out for the formulation of improved policy with avoidance of mistakes.

The nutrient removal-capacity of four chosen aquatic macrophytes was tested in both natural and laboratory conditions. Laboratory experiments were performed under controlled conditions using ‘microcosm’ methods wherein the plants were grown in three different nutrient concentrations. For field experiments, three ponds were selected that had different levels of plant nutrient concentrations and accordingly were treated as polluted, moderately polluted, and relatively unpolluted, respectively, the object being to study the nutrient removal-capacity of chosen aquatic macrophytes living in ‘natural’ conditions. For the present investigation, four common and widespread aquatic plants growing in all three ponds were chosen: Water-hyacinth (Eichhornia crassipes [Mart.] Solms), Water-lettuce (Pistia stratiotes L.), Round-leafed Water-fern (Salvinia rotundifolia Willd.), and Lesser Duckweed (Lemna minor L.). These plants were selected also because of their frequent presence in aquatic bodies in the region and their high reproductive capacity.

From the results it is revealed that, during the summer and rainy seasons, the highest content of nitrogen was removed by the Eichhornia, followed by the Pistia > Lemna > Salvinia, while during winter the highest content of nitrogen was removed by the Eichhornia followed by the Lemna > Pistia > Salvinia. Higher phosphorus removal was found in summer than in the rainy or the winter season. Phosphorus removal by the macrophytes was in the order of the Eichhornia > Pistia > Lemna > Salvinia, during the summer and rainy seasons, whereas the highest content of phosphorus was removed by Lemna in the winter months.

The nutrient removal-capacity was rated to be highest by the Water-hyacinth, followed by the Pistia, then the Lemna, and lowest by the Salvinia. It was also evident that the nutrient removal increased with increasing nutrient concentration in the wastewater. The removal of nitrate by the selected macrophytes ranged from 42.0% to 96.2%, while phosphate removal ranged from 36.3% to 70.2%. A positive and significant correlation was obtained between the concentration of nitrate and phosphate in the waters and plant tissues that were studied, and it is thought that a useful strategy to employ might be to grow the Eichhornia and the Lemna together at least where winter temperatures were likely to be low enough to favour the Lemna at that season, though at other times it is apt to be a nuisance.

Historically, remote islands and marine resources have been free for those willing to venture into their areas. Until recent years, many such islands have been effectively managed by their remote locations and any native humans. But nowadays, under-use is turning into destructive over-fishing and plundering, because there is no surveillance. Many marine parks in South-east Asia are facing the same problems as Tubbataha (White, 1989; Arquiza, 1990). Sustainable management in these areas is a challenge, especially where there are no local authorities or communities to take immediate control.

Field surveys at Tubbataha Reef in 1984 and 1989 have revealed a dramatic decline in the coral-reef quality from the incidence of dynamite fishing, the use of sodium cyanide for the aquarium and live-food fish trades, and the dropping of large anchors. Sea-turtles and seabirds are also endangered.

Solutions in areas such as Tubbataha will require organization beyond the grasp of local residents in the islands, who have traditionally had little formal government. Although they are aware of the problem, they are faced with outsiders and intruders who do not respect their conservatism. National government and/or nongovernment organizations can play a role in management, while being careful not to alienate the positive force and management control of the local communities (White, 1988a). Such issues require sensitive planning and community-based approaches that are directed at education, organization, and the involvement and building of local responsibility.

The management plan for Tubbataha Reef National Marine Park should have three thrusts and concomitant strategies: (1) to curtail immediate resource-destruction through the deployment of a team of educators, community organizers, and law-enforcement officers; (2) to articulate and implement a Park zonation plan which includes traditional fishing areas, sanctuaries, and buoys for anchoring; and (3) to implement a community development programme which will systematically integrate the adjacent fishing community into the Park management efforts and give the fishermen due responsibility in this process.

In this report we describe a method of examining the tolerance of birds to humans, namely by measuring the distance to which birds will allow a person to approach them before flying off (flush distance). We studied the tolerance of Indian birds to approaching people by recording the flush distance for 925 individuals of 138 species of residents (birds breeding in India) and migrants (birds that are not known to breed in India). Over 20% of the variance in flush distance was accounted for by the number of people situated within 50 m, the distance to the closest person, the bird's migratory status, the number of people approaching, the time of day, and the bird's total body-length (including tail).

For migratory species, 43% of the variability in flush distance was accounted for by distance to the closest other person, time of day, number of people originally within 50 m, number of people approaching, flock size, and species size. For resident species, only 18% of the variance was accounted for by distance to the closest other person, number of people within 50 m, and number of people approaching. Migrants were thus more responsive to the effect of humans, and their response was also influenced by their own size (body length) and flock size. Migratory species were less tolerant of people, flushing sooner than residents, and being more sensitive to the number of approaching people.

We suggest that resident birds in North India have become habituated to the non-violent protective behaviour of the Hindu people towards birds, whereas migrants from farther north are more wary. Alternatively migrants, being less familiar than residents with the local predators and hiding places, may be more wary than residents on their home territory. Enhanced wariness results in more time spent alert or fleeing, with resultant greater energy-demand and decreased time for feeding.