Throughout their existence, civilized peoples have been turning their environment into desert. The causes of desertification are well known—overgrazing, the felling of trees for fuel, and bad agricultural practices. Their effects are apparent in disasters such as the Sahel drought and recent famines in Ethiopia, the Sudan, and elsewhere. The population explosion enhances the extent of the environmental degradation. More agricultural land is currently being lost through salinization and waterlogging than is being created by new irrigation schemes, but this is only part of a problem that faces all tropical third-world countries and for which multinational organizations and the affluent nations of temperate regions are, regrettably and often unknowingly, largely responsible.

Because the poorer countries receive, for their agricultural products, cash of which the market value does not take into account the cost to the environment of overexploiting the land, they are apparently doomed to a vicious circle of increasing poverty, deprivation, and famine. Yet it is not beyond the abilities of civilization to devise a viable scheme, based upon sound ecological principles, by which the quality of life of desert peoples could be immeasurably improved. Instead of trying to change the land to make it conform to present economic and political expectations, development should be adapted to exploit the potentialities of the environment as it exists. Such a scheme, profiting from the diversity of microenvironments that occur in desert regions, would encompass multiple land-use and the development of numerous small agricultural and other projects—rather than the large-scale schemes hitherto initiated in fragile environments, and which have so often led to large-scale disaster. By adopting it, the world would simultaneously be made both more stable and more productive for the benefit of all its inhabitants.

As this paper demonstrates, the Philippines is undergoing much environmental degradation—mainly in the form of deforestation, soil erosion, disruption of hydrological systems, over-exploitation of fisheries, destruction of coral reefs, and extinction of species. These problems are accentuated by the pressures of a large, fast-growing and impoverished population; and they may shortly start to be aggravated yet more by climatic change in the wake of the global ‘greenhouse effect’. Moreover, and as this paper further makes plain, the environmental degradation leads to adverse economic consequences that are pervasive and profound—as may be expected in a country where several salient sectors of development are dependent upon the natural-resource base. In the long run, indeed, environmental degradation could well preclude the Philippines' prospects for sustainable development.

The alien tree species Cinchona succirubra, the Red Quinine-tree (Rubiaceae), was introduced to the Galápagos Islands, Ecuador, in 1946, for purposes of cultivation, but causes much concern as, by 1987, it was found to cover about 4,000 hectares in the highlands of Santa Cruz Island, changing the original, largely endemic, vegetation. Some limited herbicide trials have been made by the Galápagos National Park Service, but a really successful method of controlling this pest still remains to be found.

The removal of Cinchona plants from a 1000-ha Intensive Control Area (ICA) within the Galápagos National Park has been successful to date. However, large stands of the tree exist in the adjacent agricultural area of Santa Cruz Island, as well as elsewhere in the National Park. With the maturation of these stands, an increased input of Cinchona succirubra seeds to the ICA can be anticipated.

Strengthened use of manual, chemical, and biological, control measures are therefore recommended on a shortterm basis, in order to conserve the unique highland vegetation of Santa Cruz Island, Galápagos.

This study was conducted to explore the role of the mixed-function oxidase (MFO) detoxication system in the ‘adaptation’ process of gulls to polluted environments. In two different populations of Black-headed Gull (Larus ridibundus), feeding in one case in a lagoon and in the other on an inland rubbish-dump, MFO hepatic activities (aldrin epoxidase, 7-ethoxyresorufin o-deethylase, NADPH-cytochrome c reductase, NADH-cytochrome c reductase, and NADH-ferrycianide reductase) and chlorinated hydrocarbon residues were determined. All the enzymatic activities detected, and the PCB residues, were higher in the Gulls feeding on the inland dump than in the gulls feeding in the lagoon.

The results obtained suggest that the development of a strong detoxication system constitutes an important ‘survival mechanism’ for these birds when feeding customarily in polluted environments.

With ever-increasing demands being made on remote and natural lands, planners and managers require more detailed information than hitherto to assist them in monitoring the status of this wilderness resource and developing appropriate and effective management prescriptions. These requirements are addressed by a computer-based wilderness evaluation procedure that has been developed for a national wilderness survey of Australia.

The methodology, based on the wilderness continuum concept (Lesslie & Taylor, 1985), places emphasis on measuring variation in wilderness quality by using four indicators that represent the two essential attributes of remoteness and naturalness. This permits a precise assessment to be made of the wilderness resource, revealing those factors which contribute to or compromise wilderness quality. The computer-based storage and analysis of data enables surveys to be conducted over large, even continental, areas, yet at a relatively fine level of resolution that is appropriate to localized planning needs.

Trial application to the State of Victoria, Australia, demonstrates that the survey procedure can be successfully adapted to a wide range of environments, use-patterns, data-base characteristics, and management objectives, which should be applicable and very widely useful elsewhere.

Plant communities produced experimentally in twometres' square plots on the rubble-covered floor of a limestone quarry showed changes in the cover values that were attributable to the sown grass and to immigrant mosses over a period of three years. Cover values for the mosses were lower in summer than in the following autumn over two cycles, whilst the cover that was attributable to the sown grass, a non-rhizomatous cultivar of Festuca rubra, did not follow a clear pattern. No evidence of directional change was found; this suggests a stable coexistence of the grass with mosses. It is suggested that one property of such a community will be a differentiation of regeneration niches which are favourable to an increase of diversity through immigration.

Episodic persistent flooding and consequent deposition of colloidal limestone on well-established and diversifying vegetation, followed by a single catastrophic incident of compression by the tyres of heavy vehicles, resulted in the loss of F. rubra and mosses, and the ascendency of a perennial survivor (Agrostis stolonifera).

To conserve a resource without having adequate data and finance is difficult and frustrating. The situation of wildlife in Nigeria is nevertheless different. Except in the Yankari, Upper Ogun, and Kwiabaha, Game Reserves, and the Kainji Lake National Park, little efforts have been made to protect the Nigerian animal wildlife resources from human pressure and widespread extinction. To many, what remains of the wild animals are best seen in the few state-owned zoological gardens in Nigeria. However, because most indigenous large animal species—including Elephant, Buffalo, Chimpanzee, Gorilla, Rhinoceros, Leopard, and Ostrich—have not been able to reproduce in the various zoological gardens so far, the hope to conserve these animals is brittle. The questions are, what factors are working against wildlife conservation? Indeed, what hopes exist for Nigerian animal wildlife?

Animal wildlife is a declining resource in Nigeria because of unplanned land-use practices. For example, landuses in game reserves are often conflicting and contradictory. Four land-uses: timber extraction, hunting, food-crop production, and settlement, are simultaneously going on in game reserves, with little or no control measures and with no management plans. The excessive demands for land for these conflicting uses have greatly disturbed the ecosystems involved, thus making the survival of the wild animals uncertain. Specifically, the problems of wildlife conservation in Nigeria are: (a) poaching; (b) indiscriminate burning of the vegetation; (c) uncontrolled grazing activities in the reserves; (d) intensive logging for domestic and industrial uses; (e) user rights on the reserves enjoyed by the traditional owners of the land before reservation; (f) lack of adequate funds to manage the reserves; (g) ineffective legislation; (h) lack of trained manpower; (i) urban sprawl; and (j) infrastructural development of roads, electric and telegraph lines, and irrigation schemes, all within the game reserves.

The future for Nigerian animal wildlife depends on the nation's ability to conserve what is left either in their natural habitat or, at least, in zoological gardens. The task is not simple under conditions of economic depression, with inadequate manpower and without effective management of game reserves. In these circumstances, the game reserves should be reduced to manageable numbers, while state governments should win public sympathy through adequate conservation publicity and the provision of sufficient vehicles and personnel to manage the game reserves.

The policy of land-use in game reserves should be reviewed, while researches should be conducted on (a) the levels of land-use that could be consistent with maintaining wild animals in the reserves, (b) the number and species of animals hunted per year, (c) the population of animal species in the game reserves and their habitat suitability, (d) the endangered and extinct animal species and specific reasons for the decline in their populations, and (e) human problems peculiar to each reserve and ways of minimizing them.

Establishment of a planned reservoir at Stiegler's Gorge on the Rufiji River would enable a large amount of highlyvalued energy to be produced. This would represent an important national asset. But although such a large net amount of energy would be realized on a short- to mediumterm basis, its production would be negatively influenced by a variety of reservoir operation options that would be related mainly to irrigated agriculture, fisheries, and water quality, which form trade-offs with hydropower generation.

The most significant effect of the dam would be drastic reduction, by controlled discharge, in the frequency of severe floods in the lower Rufiji valley. Floods in excess of 2,500 cubic metres of discharge per second could be reduced in number from some 14 to 3 in 24 years, or from 167 to 13 during 300 years. The most devastating floods would also be reduced—from once in about 8 years to once in maybe 40 years.

The STIGO Project impact area contains a major wildlife resource in terms of size, density, and diversity. Its accessibility to Dar es Salaam gives it a great potential for tourism development. As an access road to the dam-site would be a necessary prerequisite to implementation of the STIGO Project, it would indirectly help to open up the Selous Game Reserve to tourism, which is currently being hampered by poor communications. Also, a substantial amount of the forest resources identified along this road could be exploited.

No complete populations of animal wildlife would be in danger from direct ecological consequences of river impoundment and dam construction. However, significant proportions of the populations in the STIGO Project impact area of three species (Giraffe, Wildebeest, and Zebra) would be potentially at risk, owing to their need for habitats of restricted range. On the other hand some species, including Crocodile and Hippopotamus, would increase in numbers following creation of the reservoir and improvement of their habitat downstream of the dam (due to swamp drainage).

Not withstanding that the ecological impacts of dam construction are relatively minor, the socio-economic impacts on wildlife and conservation values are potentially great—resulting, for instance, from facilitated access to the heart of the Selous Game Reserve and concomitantly increased conflict between wild animals and Man. These circumstances would reduce wilderness values and disturb animal wildlife, so that, especially, commercially valuable species may be expected to decline unless strict regulations are made and enforced.*

River impoundment would have very negative impacts on floodplain fisheries and agriculture, the latter of which would probably be changed to irrigated agriculture with artificial fertilization, while floodplain fisheries would totally collapse. Some mangrove stands in the Delta would probably be displaced by reeds. Delta fisheries would be very negatively affected, because of changes in the water regime as well as in salinity levels.

Water quality in the planned reservoir and in the downstream area would be negatively affected by the project. The water would often be unfit for human and animal consumption and use, as well as unfavourable for fisheries. The project would also have negative effects on the health of the riparian population, owing to increased potentials for disease vectors.

Overall, a high degree of uncertainty is involved in the project. The effect of the primary project (hydropower) would be negative owing to its drastic consequences for the immediate and more distant impact areas. Its image might improve and probably become positive if development in the Basin were carefully controlled and managed. This would require reliable prediction of the impacts and a thorough analysis of the remedial and/or additional measures to arrive at an integrated development strategy for the Basin. Although several measures are planned to eliminate and/or minimize the negative impacts, their implementation may be difficult in view of the bad economic situation of the country.

Lyon's conclusion (cf. 1919) with regard to the stand reduction dieback on the lower wet slope of Haleakala Mountain led to a forest management policy that saw importation of alien tree species as necessary for protecting Hawaiian watersheds. Unfortunately, this also led to a further demise of native vegetation.

It is possible that the low-canopy species diversity in Hawaii may increase the rate of paludification and swamp (or bog) formation, under wet climatic conditions, over that in a similar environment with a broader spectrum of successional species. However, a boggy landscape can also be a good watershed. Historic evidence comes from the sugar-cane planters on Maui—the supposed beneficiaries of the exotic tree-planting programme—who had objected to it on empirical grounds (Holt, 1983). A more recent study of a canopy dieback in the Hilo watershed showed that extensive tree mortality had no effect on the rate and quality of the water yield from this area. The forest hydrologist, R.D. Doty (1983), who investigated this relationship, attribut ed the outcome to the vigorous undergrowth which remained intact during the dieback event.

Further landscape ageing in Hawaii's shield-shaped mountains involves a process of fluviomorphic dissecting of the gentle slopes lying inland. This results first in amphitheatre-headed valleys and eventually, on the windward sides, in steep residual escarpments with numerous secondary footslopes. Wirthmann & Hüser (1987) derived details of this process from the side-by-side comparison of younger with older Hawaiian mountains. When the waterlogged surfaces of the plateau-like lower wet slopes of shield volcanoes become laterally drained, closed Metrosideros forests can become re-established. That this natural re-establishment process works in the Hawaiian mountains can be seen by going from the shield-shaped slopes of the younger, to the more dissected slopes of the older, high islands. Vigorous Metrosidews forests occur also on the older islands, but they are typically of lower stature than those on the younger mountains.

Unfortunately, most of the secondary slopes formed at the base of the steeply-cut windward mountain slopes of the older high islands have been deforested to make way for crop agriculture. Many of these lower slopes have subsequently been abandoned for economic reasons; but instead of reverting to forests, they have become invaded in many areas by alien grasses and shrubs. Particularly damaging has been the introduced pyrophytic Broomsedge (Andropogon virginicus). This grass has retained a temperate-zone phenology, whereby it undergoes partial dormancy during the winter season when rainfall increases (Sorenson, 1980). As such it has contributed to accelerated erosion in two ways: (1) by preventing recirculation of soil water in areas where excessive runoff is a problem, and (2) by attracting repeated fires and preventing succession to a forest, which would provide much-improved protection against the accelerated soil erosion (Mueller-Dombois, 1973) that is such a common feature on the lower windward slopes of the older islands.