Conceptualizing the built environment as a social-ecological system

Formulating a unified theory of the built environment may require that the built environment be understood as a complex social-ecological system, where multiple-related metabolisms interact at different scales. From this broad systems perspective, the dividing line between what is considered as nature and what is considered as built environment becomes a cultural attribute that changes with the historical context. Over the past four centuries, notions of environmental accounting and material metabolism have expanded from year-to-year economic and biological exchanges to energy, material, financial, and information flows extended through time and space. At present, the necessary extension of system limits in time and space is best achieved by combining a number of methods, including flow-based models and resource-conservation-based models, and top-down and bottom-up modelling approaches. Artefacts, flows, and actors can be linked over time by means of a common framework for describing the built environment, and by life cycle-oriented product modelling techniques. Despite such advances, existing theory seems incapable of fully integrating spatial and physical relationships, and is especially challenged when dealing with concepts of time. Ecological models provide a useful basis for new timing tools that integrate different time scales, past and future, and that allow for an assessment of adaptive capacity and other aspects of system resiliency. These models can be used to understand better the impact of different managerial and social policies at both the macro- and the micro-level. The management of the long-term evolution of this social-ecological system can only be assured through appropriating ecological concepts of time, and by integrating the history of nature with the history of human culture.