Measurement and evaluation of the metabolic capacity of an urban ecosystem Y. Zhang a , Y.W. Zhao a, * , Z.F. Yang a , B. Chen a , G.Q. Chen b a State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China b National Laboratory for Turbulence and Complex Systems, Department of Mechanics, Peking University, Beijing 100871, China article info Article history: Received 22 November 2007 Received in revised form 10 January 2008 Accepted 3 March 2008 Available online 15 April 2008 PACS: 89.65.Lm 89.60.Fe Keywords: Urban material metabolism Wealth index Ecological efficiency index abstract Cities as superorganisms confront disturbances from their metabolic processes, including large metabolic fluxes, low stocks of resources and products, and a low efficiency of the urban material metabolism. Based on ecological thermodynamics, an indicator system is established in this paper to evaluate the fluxes, stocks, and effiency of the urban material metabolism using emergy analysis. Also, a new model for the urban material metabolism is proposed to define the production possibility curve using a wealth index (WI) and an eco- logical effiency index (EEI). Then, six large Chinese cities including Beijing, Shanghai, Tian- jin, Chongqing, Guangzhou, and Shenzhen are selected as typical cases to validate the proposed model. The results show that Shenzhen has the highest metabolic capacity, fol- lowed by Beijing, Shanghai, Guangzhou, Tianjin, and Chongqing. It is also reflected that dif- ferent urban material metabolisms of the six cities are resulted from the varied regional metabolic capacities, thus providing insights into how cities improve their metabolic capacities. Meanwhile, Shenzhen has the highest WI and EEI, Chongqing has the lowest WI and EEI, and Beijing, Shanghai, Tianjin, and Guangzhou has low WI and high EEI. It is also shown that the sustainable operation of the urban material metabolism reflects the mutualism and symbiosis between socioeconomic development and ecological environ- ment protection. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Research on urban material metabolism can contribute to solving urban ecological and environmental problems by high- lighting the demands placed by the urban ecosystem on various resources and the pressure of its discharged wastes on the environment in and around the urban ecosystem [1]. In 1965, Wolman first introduced the concept of urban material metabolism into urban research, asserting that the oper- ation of an urban ecosystem closely resembled a metabolic process [2,3]. Later, a number of scholars built on Wolman’s ideas by treating cities as if they were organisms, and analyzing the processes and mechanisms that formed the metabolism of these organisms [4–11]. Other scholars used this evolving theory to study the material metabolisms of Toronto [1], Nantong [9], Paris [10], Sydney [12], Hong Kong [13], Taiwan [14], Manchester [15], Ningbo [16], Shanghai [17], Shenzhen [18], and New York [19]. However, the research on urban material metabolism is still in its early stages, and the main study fields have been focused on urban industrial material metabolism [8,14,15,20–23], urban household material metabolism [12,24–29], 1007-5704/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cnsns.2008.03.017 * Corresponding author. E-mail address: awei-a@163.com (Y.W. Zhao). Commun Nonlinear Sci Numer Simulat 14 (2009) 1758–1765 Contents lists available at ScienceDirect Commun Nonlinear Sci Numer Simulat journal homepage: www.elsevier.com/locate/cnsns