As a result of an increasing population, our reduced acreage of forest land will be called upon to produce maximum amounts of wood fiber, to satisfy an ever-increasing demand for recreational use, and to produce maximum amounts of clean, pure water. Under such demands, forestry must be practiced with an intensity that is beyond our ability to conceive at present. Of necessity, every tool, including chemicals, must be used in this intensive management for the good of mankind. To achieve these aims, it will be also necessary that we quickly acquire a detailed and intimate knowledge concerning the interactions that occur within forest ecosystemsnot only natural interactions among plants, but also those that occur when we artificially induce changes in structure or composition in communities or ecosystems by artificial means. Such changes may not only affect vegetation; they may also affect atmospheric, wildlife, and microbiological conditions as well. Chemicals are useful, necessary tools for helping to meet needs for food, wood fiber, and water, while man readjusts his numbers and modes of life to the rapidly dwindling resources of the earth. The more selective, less persistent chemicals will continue to play an important role in forest resource management, probably for several decades. However, chemical use must eventually be minimized, for it is simply a system of treating symptoms of unhealthy ecological conditions created by nature or man in the past. Technological, environmental, and socioeconomic factors will add new dimensions to chemical use, placing greater demands on the research and development process. Our pressing need, aside from solutions to problems of population pressures and extravagance in natural resource use, is rapid development of the ecological knowledge necessary to manage and maintain a healthy biosphere with minimum use of chemical tools.