Assessment of Ecological Benefits of Urban Green Spaces in Nanjing City, China, Based on the Entropy Method and the Coupling Harmonious Degree Model

Urban green spaces (UGSs) are an important spatial carrier for carbon sequestration in the national land space. The urban ecosystem is a highly harmonious composite ecosystem of nature, society, and the economy. Therefore, this study constructed an evaluation system of the UGS ecological benefit based on two subsystems-the natural environment and the social economy-in order to quantitatively evaluate the construction level of the UGS ecological benefit in Nanjing City and to reveal its temporal evolution characteristics. The entropy method was applied to assess the ecological benefits of UGSs in Nanjing City, China, from 2011 to 2020. The coupling harmonious degree model was utilized to analyze the dynamic coordination relations among subsystems. The Robust regression analysis was used to verify the evaluation results. The results showed that: (i) Between 2011 and 2020, UGS ecological benefits in Nanjing City exhibited a substantial and consistent upward trend. (ii) Between 2011 and 2020, the coupling harmonious degree among the subsystems of UGS ecological benefits in Nanjing City showed an overall rising trend of fluctuation. With the enhancing of the coupling harmonious degree among the subsystems of UGSs, the ecological benefit of UGSs will be significantly improved. (iii) The comprehensive evaluation score of the social and economic subsystem of UGS in Nanjing City was higher than that of the natural environment subsystem; this highlights the significant constraints posed by the natural environment on the construction of UGSs in Nanjing City. The research conclusion provides a decision basis for realizing the collaborative optimization of the natural environment and the social economy in Nanjing City and further promotes the sustainable development of the UGS ecological environment.