The earth's landscapes are being increasingly impacted by the activities of man. Unfortunately, we do not have a full understanding of the consequences of these disturbances on the earth's productive capacity. This problem was addressed by a group of French and U.S. ecologists who are specialists at levels of integration extending from genetics to the biosphere at a meeting at Stanford, California, sponsored by the National Science Foundation and the Centre National de la Recherche Scientifique. With a few important exceptions it was found at this meeting that most man-induced disturbances of ecosystems can be viewed as large scale patterns of disturbances that have occurred, generally on a small scale, in ecosystems through evolutionary time. Man has induced dramatic large-scale changes in the environment which must be viewed at the biosphere level. Acid deposition and CO increase are two 2 examples of the consequences of man's increased utilization of fossil fuels. It is a matter of considerable concern that we cannot yet fully predict the ecological consequences of these environmental changes. Such problems must be addressed at the international level, yet substantive mechanisms to do this are not available."

This volume is based on a workshop on "Population Biology of. Plants The Interfaces (Genetics, Physiology, Demography, Biogeography)," with a specific profile on "Diversification of Plant Populations in relation to Modes of Reproduction and Dispersal Genetic and Physiological Mechanisms," held in Port-Camargue, France, from May 21-25, 1984. This workshop was initiated by the "Unit of Population and Community Biology," in Montpellier, and sponsored by the NATO Scientific Affairs Division (ARW grant 876/83) and by the CNRS (Table ronde). All populations are subjected to environmental "screening." Given a genetic diversity whose expression can be modified by a degree of demographic and individual plastici ty (at the morphological and physiological levels), they present a structure related to their environment. Ideally populations should be studied simultaneously from the point of view of the population geneticist, the physiologist and the demographer . These specific approaches only become fully meaning full in the "light of Evolution." Among the evolutionary forces that quantitatively act on the frequencies, objects of interest of workers specialising in Population Biology are selection and drift. An other main object of the study must be dispersal. But, its playing extent - relative to the other forces - in the adjustment to the environment is not fully recognized.