Time Series Analysis on Ecological Competitive Capacity of Beijing Using Emergy Synthesis

An emergy-based analysis was conducted to investigate evolvement of the ecological competitive capacity of Beijing with regard to urban evolution and city development from 1990 to 2005. A newly integrated indicator, ecological competitive capacity index (ECCI) was established by combing conventional emergy indices of percentage of local renewable resource, emergy self-sufficient ratio, emergy/money ratio and waste emergy ratio, to reflect the overall performance of urban system with respect to their long term sustainability. The result shows that the intensity, structure, efficiency and their environmental impact associated with urban emergy use have exhibited diversified changing tendency. However, the ECCI has decreased with fluctuation from 1990 to 1999, but remains relative stable after 1999. The maximum vale of 1 can be found in 1991 while the minimum value of 0 in 1997 among the concerned years. How to enhance the urban ecological capacity and strengthen the capability of sustainable development is an urgent issue confronted by large cities as Beijing.