During the summer of 1987, a series of discussions I was held at the International Institute for Applied Systems Analysis (nASA) in Laxenburg, Austria, to plan a study of global vegetation change. The work was aimed at promoting the Interna tional Geosphere-Biosphere Programme (IGBP), sponsored by the International Council of Scientific Unions (lCSU), of which nASA is a member. Our study was designed to provide initial guidance in the choice of approaches, data sets and objectives for constructing global models of the terrestrial biosphere. We hoped to provide substantive and concrete assistance in formulating the working plans of IGBP by involving program planners in the development and application of models which were assembled from available data sets and modeling ap proaches. Recent acceptance of the "nASA model" as the starting point for endeavors of the Global Change and Terrestrial Ecosystems Core Project of the IGBP suggests we were successful in that aim. The objective was implemented by our initiation of a mathematical model of global vegetation, including agriculture, as defined by the forces which control and change vegetation. The model was to illustrate the geographical consequences to vegetation structure and functioning of changing climate and land use, based on plant responses to environmental variables. The completed model was also expected to be useful for examining international environmental policy responses to global change, as well as for studying the validity of IIASA's experimental approaches to environmental policy development.

During the summer of 1987, a series of discussions I was held at the International Institute for Applied Systems Analysis (nASA) in Laxenburg, Austria, to plan a study of global vegetation change. The work was aimed at promoting the Interna tional Geosphere-Biosphere Programme (IGBP), sponsored by the International Council of Scientific Unions (lCSU), of which nASA is a member. Our study was designed to provide initial guidance in the choice of approaches, data sets and objectives for constructing global models of the terrestrial biosphere. We hoped to provide substantive and concrete assistance in formulating the working plans of IGBP by involving program planners in the development and application of models which were assembled from available data sets and modeling ap proaches. Recent acceptance of the "nASA model" as the starting point for endeavors of the Global Change and Terrestrial Ecosystems Core Project of the IGBP suggests we were successful in that aim. The objective was implemented by our initiation of a mathematical model of global vegetation, including agriculture, as defined by the forces which control and change vegetation. The model was to illustrate the geographical consequences to vegetation structure and functioning of changing climate and land use, based on plant responses to environmental variables. The completed model was also expected to be useful for examining international environmental policy responses to global change, as well as for studying the validity of IIASA's experimental approaches to environmental policy development.

The response of forests to global climate change is one of the most hotly contested issues in the greenhouse effect debate. Much effort is being devoted to the construction of models which describe the function of the forests and their rate of change. There are a wealth of techniques available to project large-scale vegetation patterns, all based on different underlying models that contain fundamental biological and ecological mechanisms. Vegetation Dynamics and Global Change will introduce both students and professionals to the sophisticated mathematical and computational tools used to predict the rate of change in the world's forests. It emphasizes the importance of scale in global studies. Leaders in the field of vegetation modeling cover physiological phenomena typically measured at small time and space scales; the stand dynamics of forests; large-scale models of forest dynamics; the reconstruction of forest vegetation of past climates as a way to understand current global changes; and the role of forests in the global carbon cycle. Several themes run through the book, including the need to understand how processes important at one time and space scale can be conceptualized at larger scales; the need to optimize the conceptual benefits of representing processes in detail and the attendant difficulties of estimating parameters and designing tests for elaborate models; and the need to identify the most appropriate system variables.