Modeling the urban ecosystem: a conceptual framework

In this paper I build on current research in urban and ecological simulatio n modeling to develop a conceptual framework for modeling the urban ecosyst em. Although important progress has been made in various areas of urban mod eling, operational urban models are still primitive in terms of their abili ty to represent ecological processes. On the other hand, environmental mode ls designed to assess the ecological impact of an urban region are limited- in their ability to represent human systems. I present here a strategy to i ntegrate these two lines of research into an urban ecological model (UEM), This model addresses the human dimension of:the Puget Sound regional integr ated simulation model (PRISM)-a multidisciplinary initiative at the Univers ity of Washington aimed at developing a dynamic and integrated understandin g of the environmental and human systems in the Puget Sound. UEM simulates the environmental pressures associated with human activities under alternat ive demographic, economic, policy, and environmental scenarios. The specifi c objectives of UEM are to: quantify the major sources of human-induced env ironmental stresses (such as land-cover changes: and nutrient discharges); determine the spatial and temporal variability of human stressors in relati on to changes in the biophysical structure; relate the biophysical impacts of these stressors to the variability and spatial heterogeneity in land use s, human activities, and management practices; and predict the changes in s tressors in relation to changes in human factors.