Measurement and evaluation of interactions in complex urban ecosystem

Abstract

The objective of this study is to measure and evaluate the interactions among various variables in the complex urban ecosystem (CUE), through employing an equilibrium model, a metabolism model and a harmonious development model. Based on a theory of the complex urban ecosystem (including society, economy and nature) with metabolic function, a system of indicators is developed for evaluating urban ecosystem, through using factor analysis (FA), the analytic hierarchy process (AHP), and a synthetic index. The urban metabolism model and the urban harmonious development model are constructed and then are employed to measure and evaluate the interactions among various variables for Beijing, Shanghai, Guangzhou, Tianjin, Chongqing, and Shenzhen. The urban metabolism model illustrates how the conversion of resources into useful products and wastes is similar to human metabolic processes or those of an ecosystem, and accounts for how the basic metabolic concept has been extended to include the livability of the CUE from a human perspective so that the socioeconomic aspects of sustainability are integrated with the environmental aspects. This means that the best way to reduce the impacts of socioeconomic development would be reduction of the resource inputs. On the other hand, the sustainability of development of a city is not only simply reduction of the metabolic flows (resource inputs and waste outputs), but also increase of the livability of the city, measured here by the recycling degree. There are two potential ways to purify the metabolites produced by the CUE: (1) reclamation of wastes, (2) making wastes harmless for the natural ecosystem. The harmonious development model presents the urban developmental trends by the developmental degree and the harmonious degree in response to the relationships between development pressure and carrying capacity in CUE. This model shows that the socioeconomic development pressure and the carrying capacity of the natural ecosystem are competing processes, and that ecological improvement is most possible when the socioeconomic development pressures are small and the carrying capacity of the natural ecosystem is large. At last some conclusions drew about the recycling degree, developmental degree, and the harmonious degree in six Chinese cities show that the key factors of urban sustainable development are the decrease of socioeconomic development pressure, the protection of natural ecosystem, and the raising of urban metabolism function. To reach such goals, each city must strengthen its potential for sustainable development, and must consider the recycling degree and the harmonious degree to define the break-even point for improving the health and livability of CUE.