Kerkini Lake in Greece, a reservoir maintained principally for agricultural irrigation purposes on the Strymon River, has been classified as a ‘Wetland of International Importance’ according to the Ramsar Convention. Hydrological conditions favoured the formation of a shallow, very productive lake, rich in species diversity and biotic abundance. The importance of the wetland lay in its complex zonation of various habitats which mainly consisted of: shallow open water with sand-strips, beaches, and mud-flats; shallow-water areas with communities of emergent vegetation; a lowland hardwood riparian forest mainly of Salix and Tamarix species; a shrub-swamp; and extensive wet meadows. The diversity of habitats supported a rich waterbird fauna for breeding, stationing during migration, and wintering.

Nevertheless, in 1982 a new high-dam was constructed, higher embankments along the banks of the Lake were established, and other works were carried out (to increase the water capacity of the reservoir), in response to irrigation demands. No consideration was given to the wetland resources. Operation of the new dam resulted in changes in the flooding etc. regime, with severe impact on the biotic resources of the wetland, especially by waterlevel increases of more than 5 m in less than 4 months during spring — the critical growing- and breedingseason. Wetland heterogeneity and the mosaic structure of water-land-vegetation were thereby lost.

Now the riparian forest is diminishing in area and declining in productivity, the reed-swamp with emergent macrophytes has been lost, and wet meadows have also disappeared. Deep flooding and the loss of these habitats is reflected in marked decline in the densities of migratory waterbird populations and, most important, in drastic shrinkage in the populations of breeding species. Similar impact is observed in the dramatic decline of fish species diversity and abundance. In general, nowadays, Kerkini presents an alarming example of loss of biodiversity and accelerating impoverishment of its former biotic resources.

In view of the projected plans to increase further the water-storage capacity of the Lake by raising its waterlevel, measures are urgently needed: (a) for preventing such actions; (b) for restoring and maintaining marsh conditions, and (c) for ecologically sound management and sustainable use of the wetland resources.

The varying reasons are outlined for needing to control the movements or otherwise manage a wide range of African animal wildlife species by means of fencing. In all cases there is an underlying conflict of interest between people and animals — principally the larger mammals. Fencing is seen as the most powerful tool in this process of land-use division, and high expectations of fences are held by people who are adversely affected by wildlife activities and similarly by many conservationists. To date the main determinants in the siting and construction of fences have been political pressure or the availability of funds; wildlife fencing is perhaps the only factor having a substantial influence on ecosystems and animal populations that has remained virtually devoid of any serious input of ecological knowledge, of systematic investigation, or of environmental legislation.

The wild species requiring management are many and varied in individual size, group size, and dispersal patterns; they also exhibit an array of special behaviours when confronted with a barrier. This means that any barrier will come under very variable levels and types of challenge, and that the effects of it on the biology of both target and non-target species must be carefully considered.

Research on the behaviour of animals at fences has been limited, being mostly confined to domestic species or non-African wildlife. Certainly, very little systematic investigation has been carried out to determine whether fences have achieved their objectives or been economically justified, and to what extent they have caused environmental side-effects on the population dynamics of animals or the disturbance of plant communities.

Current evidence suggests that electric or power fences are an increasingly efficient way of managing wild mammals and that fencing programmes should become more deflecting than encircling. Fences create ‘hard edges’ between dissimilar forms of land-use and cause long-term inflexibility that limits planning and forecloses options. As the pressure for land becomes more and more acute, the control of wildlife with the help of fences needs to develop into a specialized field of its own, based on sounder ecological, sociological, and economic, principles than hitherto, within the expanding scope of adaptive wildlife management.

Export of aquarium-fish from the Maldives began in 1980 and in 1989 almost 54,000 marine fishes, worth approximately US$ 130,000, were exported. The collection of aquarium species is confined to a relatively small area around the capital island, Malé. Estimates of annual exports of 95 species were obtained by examining packing-lists held by Maldivian Customs. In parallel, the population densities of about 70 aquarium-fish species were estimated by visual assessment. Using a number of assumptions, potential (maximum sustainable) yields for 65 of these species — those for which export data were available — were estimated for the area (530 km2) within a 13-km radius (one hour's journey by local boat) of Malé.

For 27 species there were some reasons for concern about the levels of exploitation, although only 12 of these species appeared to be ‘at risk’ in 1986 (the year of highest exploitation). If the assumptions made in estimating potential sustainable yields were valid, these 12 aquarium-fish species were being overexploited or exploited at levels close to maximum sustainable yields. Should the trade expand threefold, a further 12 species are considered to be potentially at risk of overexploitation. Two species of butterflyfish, Chaetodon meyeri and C. triangulum, which feed exclusively on coral polyps and generally die in captivity after a short time, were being exported in significant numbers. Both clownfishes (Amphiprion spp.) and their host sea-anemones were being heavily exploited. Because of the symbiotic relationship between these fishes and their anemone homes, this group may be particularly susceptible to overexploitation.

Damage to branching corals may result from the collection of specimens of Dascyllus aruanus, which shelter within them. With many thousands of individuals of this species being exported each year, this could represent considerable collateral coral damage. Although levels of exploitation of ‘cleaner wrasses’ (Labroides bicolor and L. dimidiatus) appear well below potentially sustainable ones, it is unclear whether the health of reef fishes might locally be adversely affected in heavily exploited areas.

Monitoring and regulation of the aquarium-fish trade is discussed, together with the need for collection of catch statistics by those involved in the trade. The importance of regulation of collection techniques, of standards of facilities, and of satisfactory packaging of fish for export, is stressed. If more accurate estimates of sustainable yields are to be obtained, there needs to be monitoring of populations of key aquarium-fish species in designated collecting areas where exploitation levels are known. Until such estimates become available, the cautious approach adopted in the Maldives to estimate yields and set species-based quotas will, it is hoped, prevent local overexploitation.

This article examines, through a molecular perspective, the ‘ozone-friendly’ refrigerants R-134a and R-123 vis-à-vis R-12 and R-11, which are targeted to be phased out under the Montreal Protocol on Substances that Deplete the Ozone Layer, Final Act (1987). It appears that the molecular weight, size parameter, and dipole moment, of R-134a and R-123, may induce a pronounced effect on the chemical equilibrium of ice particles in the polar stratospheric clouds and subsequently influence the photochemical reactions therein.

Non-polar, high-molecular-weight perfluoropropane (R-218), could be a better substitute for R-12, while R-134, which is a non-polar HFC of the ethane family, could also be a candidate although its molecular weight is lower than that of R-12. The search for a good substitute for R-11, however, must continue.

Rural communities in northern Botswana had negative attitudes towards animal wildlife even though they received benefits from it. The negative attitude was caused by wildlife damage to crops, losses of livestock to predators, loss of land to conservation, and lack of control over animal wildlife resources. The benefits derived from animal wildlife, such as the possibility of hunting, meat, cash income from animal products, and employment in the wildlife industry, were not highly valued, even though these benefits are of considerable importance to the local community (e.g. much of the local employment is wildlife-related).

Respondents who had fewer livestock and were more dependent on wildlife for protein, were more negative than others in their attitudes to animal wildlife. The beneficiaries of the wildlife industry were largely perceived as being the hunting and tourist companies. Respondents who were more affected by animal wildlife, those living closer to higher population-densities, and those having more crop losses, were more negative than others in their attitude to wildlife. The communities were distrustful of government motives and had a poor opinion of the Department of Wildlife and National Parks (DWNP).

It is suggested that the present wildlife development programmes in this region of Botswana are likely to fail unless a change in approach is adopted by the local populace. Essential to our mind for the success of these programmes is the reduction of the negative impacts of animal wildlife, through, for example, fencing of agricultural land, improved control of problem animals, and adequate compensation schemes. It is also essential that local communities be given more control over the wildlife resources than they currently enjoy.

Examined here is the impact exerted by the military sector of human society on national parks and other protected natural areas. Disruption during wartime, both by regular and by insurgent armed forces, results largely from the collateral effects of their operations and weapons as well as from illegal logging, hunting, fishing, and pillaging. Disruption during peacetime results largely from training exercises and poaching.

A number of actions are suggested to mitigate the military impact on protected natural areas, among them: enhanced environmental education and training (in both the civil and military sectors), greater local participation in the management of protected natural areas, creation of greater respect for an expanded system of demilitarized World Natural Heritage Sites, and especially the nurturing among all peoples of a greater respect for Nature.

In reviewing the results of our analyses of European temperature and precipitation data, we see patterns that are similar to those discovered in our prior studies of the United States and the British Isles: precipitation begins to increase at about the time that Northern Hemispheric SO2 emissions began their rapid ascension, while prior upward trends of surface-air temperature are dramatically truncated.

We also find that surface-air temperature trends of different localities over the past three-and-a-half decades are closely tied to the amount of aerosol sulphates in the atmosphere above them. The wide range and thrust of these several observations, along with their theoretical expectation, provides strong support for the premise that anthropo-generated climate change is indeed occurring in Europe, but that it may well be SO2-induced rather than CO2-induced.

Major oil-spills, such as occurred following the grounding of the tanker Exxon Valdez in March 1989 in Prince William Sound, Alaska, account for only a small fraction of the total anthropogenic input of petroleum to the marine environment. Yet major spills can result in significant and even acute impacts, trigger ecological changes requiring decades for recovery, and command considerable public attention. Thus catastrophic oil-spills in general, and the Exxon Valdez spill in particular, differ from other chronic human alterations of coastal marine systems.

Estimates of the fate of the 38,000 metric tons of crude oil lost by the Exxon Valdez are imprecise, but perhaps 30–40% evaporated, 10–25% was recovered, and the rest remains in the marine environment. Roughly 1,500 km of coastline were oiled in varying degrees. Much of this coastline consists of gravel beaches into which oil penetrated to depths as great as 1 m.

The ecological effects of the spill on the marine environments of Prince William Sound and adjacent coastal areas of the Gulf of Alaska were extensive, but natural recovery, aided by clean-up efforts, is expected. Judging by the consequences of other oil-spills affecting rocky shorelines, as well as previous natural and anthropogenic disturbances to Prince William Sound, it appears likely that most affected biotic communities and ecosystems will recover to approximately their pre-spill functional and structural characteristic within from five to twenty-five years.

This oil-spill had major social effects. Many individuals, whether personally present or viewing the spill around the world on television, were saddened by the environmental damage, and felt that an important public trust had been broken. These feelings, together with dissatisfaction with the results of early clean-up efforts, gave rise to popular sentiment in favour of every possible clean-up and mitigation effort — regardless of cost, effectiveness, or possible negative consequences.

The response to the Exxon Valdez oil-spill by government and the oil industry revealed serious inadequacies in the plans and institutions for dealing with major marine oilspills in the United States. Attempts to recover spilled oil, and to respond to the spill's environmental consequences, were hampered by a low level of preparedness and lack of clear agreement about the goals of response efforts. Attempts are under way to improve oil-spill prevention and response capabilities in Alaska and the rest of the United States. However, these efforts are not yet complete, and it remains to be seen whether an improved response will be made to the next major oil-spill.