In this article we attempt to define the modeling issues facing this new type of 'urban ecology,' which will strive to understand people and their urban behavior in the inclusive way the first ecologists tried to understand remote tropical isles-defining and studying the interactions between people and the so-called natural environment in which their cities exist. In our view ecosystems span a continuum, from the pristine to the urban, along which the role of human activity grows from marginal to dominant. As ecologists, we have begun examining city-fringe expansion with the tools of ecology. Yet we hope that analyzing which patterns and dynamics we fail to capture with this approach will allow us to understand where the most important contributions from the social sciences can be made. Similarly, examining our failure to capture pattern even after incorporating the contributions of the social sciences will help us to understand where a return to the biological basis for the evolution and development of cultures might advance further understanding.