The findings of four groups of ecologists are synthesized in chapter I of this report on global ecological problems prepared as a data base for the United Nations Conference on the Human Environment. The other chapters contain the reports of each group. In "Cycles of Elements" the biologically important elements, phosphorus, sulfur, and nitrogen, are considered in detail, including related problems of air and water pollution and the possibility of depletion of phosphorus supplies. "Ecosystems for Human Benefit" contains discussions of the problems of ecosystem management, including modern agriculture and the effects of the accumulation of toxic pesticide and heavy metal compounds. Case studies of land use in five systems are used to illustrate "Ecological Aspects of Land Management.""Management of Aquatic Resources" examines the food potential of oceans and lakes, strategies for fishery management, and the effects of pollution on aquatic ecosystems. An index to recommendations concerning international cooperation, public education, data collection and analysis, technical and financial assistance, research design and development, standards, regulation and control, and the preservation of species is provided, together with a glossary of ecological terms and a general index. (AL)