The tropical American shrub Clidemia hirta (Koster's Curse) has become a pest in pastures, cropland, and forests, where it has become naturalized in many parts of the humid tropics. It has spread through the island of Oahu, Hawaii, since 1941, despite attempts at biological control by the introduction of the parasitic thrips, Liothrips urichi, which had proven effective in supressing growth of this noxious weed in Fiji.

The pest has colonized habitats similar to those occupied over its natural range—such as forest clearings, trail-sides, and burn-sites. In addition, in Hawaii it has intruded into the understorey of forests which were formerly free from exotic weeds. Fears are held that the resulting ecological disruptions may place further stress on the frail island ecosystems and cause plant and animal extinctions while producing other management and aesthetic problems.

Immediate action is necessary to eradicate small colonies of Koster's Curse that have become established on near-by islands, and recommendations are made regarding efforts needed to devise means to control heavy infestations in the highly inaccessible mountains of Oahu.

The evolving conservation views and movements in the United States are characterized by their changing social goals and the resultant alteration of attitudes towards the physical environment. Our examination results in a six-stages classification of conservation views: (1) the naturalist view, which was based on the idea of undisturbed harmony of Nature; (2) the utilitarian view, which was highly influenced by Gifford Pinchot's conservation philosophy of ‘common goods for common men’ in natural resource use; (3) the ethical view, which resulted from an awareness that increasing consumption combined with increasing population would deplete resources and depress living standards; (4) the developmental view, or a technocratic approach to resource development, which rejected a fixed inventory of natural resources and perceived an everincreasing resource base; (5) the aesthetic view, which valued the aesthetic contribution of natural resources more than the economic contribution, i.e. amenity value versus commodity value of natural resources; and (6) the ecological view, which is based on the concept of an ecosystem wherein Man is an integral and inseparable part of the total environment and is responsible for the maintenance of the total environment.

These conservation views of the United States reflect a historical conflict between progressivist and preservationist philosophies of natural resource use. The conflict derives from changing societal concepts of resource scarcity regarding their physical, economic, or qualitative, aspects. The current ‘ecological’ view remains uncertain in terms of its concept of scarcity.

Arab oil money is currently being invested in agricultural development of the Sudan. To halt desert expansion and to develop arid regions are different problems, however. The former could not be achieved without stronger political and sociological measures than would be acceptable to the inhabitants. The latter may be financially rewarding, but agricultural schemes may be attended by considerable risks that are often overlooked until too late.

It is argued that small improvements may prove to be sounder investments than grandiose schemes, and that the latter, if adopted, should always be tested by experimental pilot projects prior to any wide implementation.

Ecological interrelationships are far less complex in the desert biome than they are in grassland or forest but, even so, they are little understood. Some of the better known are described, but none of them is relevant to desertification. Harmful insects, such as locusts, grasshoppers, and termites, are unlikely to be responsible for extension of desert, except when they intensify environmental changes that have already been initiated by Man. Similarly, mammalian herbivores, even if protected and allowed to attain far greater population sizes than at present, are most unlikely to cause harm, as they are highly nomadic and always on the move.

These relationships hold true despite the fact that the natural predators of desert mammalian herbivores have largely been eliminated by human activities.

Large areas of Papua New Guinea are covered by tropical rain-forest, but national and local pressures for development are causing increasing areas to be cleared for agriculture or logged for timber. Despite concern by conservation-minded land managers, a number of constraints make planning for the rational use of these resources rather difficult.

The problems encountered are mainly sociological rather than ecological. Thus while landowners are willing or eager to sell the rights to harvest the timber on their land, they are unwilling to commit the land to any long-term land-use, whether this be as managed forest, national park, or wildlife reserve. The problem is compounded by the complicated system of land tenure and the fact that several language-groups may commonly be found within even a small area.

The Gogol Timber Project at Madang illustrates some of these difficulties and the attempts that are being made to overcome them.

Reservoir storage projects are known to alter significantly the environmental settings in which they are established. Extensive data are required to assess quantitatively the physical effects of human interference with rivers. Methodologies must be developed to permit continual monitoring of such changes, so that environmental effects of storage projects may be considered in more integrated, comprehensive plans than hitherto for future river-development efforts.

This study documents stream-channel changes over a five-years period following reservoir completion at eight cross-sections on the main stream below a dam and on one tributary. Of eight main-stream sections, four are increasing in cross-sectional area, namely numbers one, five, six, and seven. Of these, the crosssectional area of numbers one and seven is increasing laterally and that of five and six is increasing vertically. The average annual degradation of sections five and six is 0.092 m over the study period, compared with an average of 0.031 m in the United States over the first 10–15 years after dam closure. Sections three, eight, and nine, are shitfing laterally without a crosssectional area increase, while of sections 2 and 4 the cross-sectional area remained largely unchanged.

Extraction of most of the sediment load by the new reservoir led to increased erosion of the stream channel below the dam. However, it is not always predictable whether the increased erosive power of released clearwater will induce the ongoing channel to erode its bed, widen its section, or cause the bed to move laterally. Nearly all of the nine Deer Creek study sections experienced one of these changes over the study period of five years.

Among the larger mammals, marine types offer some unique insights and problems for management. United States laws require that they be managed ‘to maintain the health and stability of the marine ecosystem.’ The relevant statute (Marine Mammal Protection Act of 1972) requires maintenance of an ‘optimal sustainable population’, which is being interpreted as a range between the level giving a maximum sustainable yield (MSY) and asymptotic levels. Emerging evidence pertaining to marine mammals, and perhaps applicable to a larger class of vertebrates, indicates that the MSY point may be well above the logistic-curve 50% point.

‘Reproduction curves’ of various sorts are used in management as operational representations of population self-regulation (density-dependence). A variety of theories and hypotheses concerning such regulation now exists, though none is adequately supported as yet. A general model for self-regulation in long-lived species is suggested as being comprised of stages of regulation. Immature mortality is postulated as the first stage, followed by age of first reproduction and then reproductive rates of adult females. The fourth and last stage, as populations reach maximum sustainable levels, is assumed to involve changes in adult survival.

Although a model of the kind suggested here offers some useful insights as to harversting strategies, a more quantitative (functional) basis will be needed for actual management applications.

Bushmeat is meat, of whatever nature, that is obtained from wild animals, and historically people everywhere in the inhabited world have, at some stage in the evolution of their culture, been dependent on it to some extent. Wildlife conservation is essential for varied bushmeat production, and the two are particularly closely interconnected in the countries of Africa lying to the south of the Sahara; this brings in environmental conservation as a third factor of basic importance.

The economic incentive being often considerable, the record of protection and management of wildlife in some countries in Africa south of the Sahara is impressive, though in others it is lagging, while even in the famous National Parks the failure to cull large mammals may lead to drastic habitat deterioration due to over-population: wider, regularized use of bushmeat could provide a beneficial answer to this problem. Meanwhile there is a great demand for bushmeat in Ghana and many other African countries, and it is expected that this demand—and hopefully the supply—will increase with changing patterns of land-use.

There is thus strong economic and other justification for environmental management with the objective inter alia of maintaining and increasing bushmeat production in most countries of Africa south of the Sahara.

The suggestion, made in two earlier papers, that the use of a standard discount rate is not appropriate the planning of the environment, is considered further. It is concluded that the approach suggested in those papers may be of general validity in investment and cost/benefit decisions of all types. This approach involves an assessment of risks, together with an assessment of the expected ratio of investment: income.

The experiment described was conducted in water impounded by earth dams, for local water-supply, in Nyanza province, Kenya. Control of snails was attempted by introduction of the malacophagous fish Astatoreochromis alluaudi; other species were also introduced. The schedules of introduction of fish were varied between the reservoirs, and one was left as a control without any introduction of fish. The necessity for the establishment of a fish-rearing pond, prior to large-scale stocking, is emphasized.

Assessment of snail control was made by scooping for snails, catches being expressed per man-hour. This was carried out both before and after introduction of fish, over a total period of 15 years. It is concluded that the data indicate that A. alluaudi did reduce the numbers of some species of snails—particularly Biomphalaria pfeifferi and, to a lesser extent and with less certainty, Bulinus spp.

Two other introduced fish species, Tilapia zillii and T. leucosticta, did not appear to be associated with any fall in snail numbers.