A city's metabolism: Towards the sustainable development of urban systems

Abstract

Efforts to achieve development in densely populated regions have to focus on the settlement areas with their stocks in buildings and transportation networks. In chemical kinetics, the “slowest step” within a series of connected steps of transformation determines the time of the entire transformation. Analogously, the rate of transformation to sustainability of urban systems such as the one we have described in this paper, would be determined by its “slowest step"—the transformation of the stock of buildings and transportation networks. Because of economic and technical factors, that transformation would take two generations, or approximately 60 years. The capital invested in the stock of the buildings and transportation networks (See “Buildings and Underground” in Figure 5.) of the KSM region amounts to $US300,000 per capita. The annual expenditure for the stock's metabolism is $US 10,000 per capita. This amount is within the same order of magnitude as the annual net income per capita ($US35,000). Assuming an annual change of 1–2 percent of the stock, it would take about 60 years to reconstruct the urban system. In conclusion, our study of one urban area's “metabolism” indicates that if sustainable development is to occur, the region will have to modify drastically its settlement stock and replace the materials it currently uses for energy transformation. The management of the region's other three “mass goods” (water, biomass, and construction materials) could more easily be modified and, therefore, could more easily be made sustainable.