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.

The major anthropogenic sources of heat pollution in 1989 have been identified, and the ultimate heat generated has been calculated. Those sources include the combustion of fossil fuels and of biomass, nuclear fission, and the burning of forests. The total rate of heat generated from such sources for the world as a whole, 16 to 26 TW, is compared with a very approximate estimate of the heat retained at the Earth's surface, 291 TW, resulting from decreased radiative heat-loss due to increased concentration of atmospheric CO2. However, heat pollution may be more important than the ratio of about 5 to 9% would appear to indicate. It is a direct process producing heat at the surface of the globe, not subject to moderating feedback mechanisms, and is expected to be most pronounced at land-based sites marking centres of high industrial and other human developments. On the other hand, global warming due to increased atmospheric CO2 is an indirect process that is dependent on many factors, not all of which are known or measured — such as the extensive smoke-clouds resulting from the forest fires in Amazonia. Compared with preindustrial times, the rate of heat pollution has grown by a factor of more than forty.

The dynamics of a Pinyon Pine-Utah Juniper woodlands community were studied to determine the baseline conditions and the annual variation in the major plant components. Understanding the normal baseline community status and its annual variation is paramount to evaluating the possible impact of an air pollutant on the system. Environmental impact assessments rarely concern data from more than one or two years, yet results of the present study show that annual variation is such that data from several years are necessary to establish a valid baseline for community structure.

Barren, desert-like environments have been created over large areas in Afghanistan, and various degrees of desertification can be seen especially in the southwestern plains. Extensive overgrazing, frequent drought, and unwise land-use, have initiated processes of local desertification also elsewhere in Afghanistan.

The first step in the restoration of depleted vegetation is to correct the improper uses that have been responsible for these conditions. Improper grazing practices of rangelands are a primary cause of reductions in the productivity of arid and semi-arid ecosystems in Afghanistan.

The second step in restoration is to prepare a detailed revegetation plan. The following maps and information are needed: (1) a vegetation-cover map, (2) a soil-series map, (3) a topographic map, and (4) baseline data on climatic conditions. The vegetationcover map identifies the plant biomass potential and the species that might be suitable for revegetation. The soil-series map is accompanied by a description of the physical and chemical features of the topsoil and subsoil along with an assessment of the general herbage production potential. The topographic map helps with species selection and planting methods. The climatic parameters assist in determining the season of planting and any need for drought-resistant species to be planted.