Useful indicators of urban sustainability: Some methodological issues

This paper considers methodological questions concerning indicators of sustainability, which have arisen in the course of an EPSRC-supported project investigating a systems approach to assessing the sustainability of cities. The project aimed: (a) to develop a methodology, the Reference Sustainability System (RSS), for representing the energy, resource and material flows, on which the environmental sustainability of cities depends; (b) to show how this methodology could contribute to a more systematic assessment of the potential of technological and resource management strategies to enhance urban sustainability. Systems models of the material or resource flows caused by the household demand for paper, energy, water and bottled water have been constructed. The project has highlighted the complexity of assessing the contributions of specific technologies and strategies to enhanced sustainability. Particular issues raised include the relative merits and problems of using externality valuation methods compared to physical indicators, the difficulties of aggregating environmental impacts, the question of where system boundaries should be drawn in a life cycle analysis, and the need to consider both distant and local impacts which arise from the end-use demands of urban populations. The paper explores these issues, through the use of modelling results from the case studies. Particular emphasis is placed on the communication of research results to policy makers, interested organisations and the public, drawing on recent experience with the dissemination of results from the project's first case study relating to waste-paper management options.