Sustainable development and green gross domestic product assessments in megacities based on the emergy analysis method—A case study of Wuhan

Globally, cities are generally facing challenges of sustainable development, and this is particularly true in megacities. To reveal the relationship between economy and ecology, green gross domestic product (GDP) represents the ideology and requirements of sustainable development. In this study, emergy analysis theory is introduced to the green GDP accounting system and to a sustainable development evaluation framework using Wuhan City from 1994 to 2015 as a case study. The results show that (a) the green GDP increases as traditional GDP grows year by year, indicating the improvement of the sustainability development of Wuhan. (b) In terms of green GDP contributing factors, the proportion of nonrenewable energy in traditional GDP decreased from 11.91% to 5.31%, reflecting remarkable progresses in the promotion of saving energy. (c) In terms of the sustainability dynamic assessment, result greater than one for the Emergy Sustainability Index implies the economic system of Wuhan following a trajectory of sustainable development, but the downward trend of the Environment Index of Sustainable Development in recent years indicates that Wuhan needs to improve its socioeconomic performance. Based on the emergy analysis, this study provides a theoretical framework for investigating and assessing the temporal characteristics of green GDP accounting, urban sustainability assessment, and inhibiting factors in the progress of sustainability. Empirical findings provide theoretical support and policy recommendations for the promotion of urban sustainable development.