In this text, written for the general reader rather than for the specialist, the accelerating use of man's environment is considered from agricultural, economic, demographic, and land and other resource use, with principal reference to the United States situation, but with reference to the world scale when appropriate. Environmental threats are classified into those that produce a loss of amenity (including aesthetic aspects), affect human health, produce genetic and reproductive changes, or influence ecological systems, particularly the "life support" factors. The same change may have effects in each of the categories proposed. Five major hazards (climatic change, radioactivity, pesticides, fertilizer misuse, and erosion) are treated in detail, and the pollution effect on the receiving media of water and air is examined. Possible methods of coping with these problems are reviewed, and some more general factors, primarily social, influencing the chances of action are then briefly surveyed. The bibliographies contain selected references to the problems discussed in the text. (AL)