Assessing urban ecosystem health using emergy and set pair analysis: a comparative study of typical chinese cities

• Emergy-based urban ecosystem health indicators (UEHIem) was created, considering the varied energy. • This paradigm analyses five critical dimensions: vigor, structure, resilience, maintenance of ecosystem service functions. • The approximate degree of index sets compared to the optimum one, facilitating a relative assessment of urban ecosystems. Urban ecosystem health evaluation has become increasingly critical as Chinese cities face mounting environmental pressures and resource constraints. This study proposes an integrated framework that combines the emergy-based Urban Ecosystem Health Indicator (UEHIem) with Set Pair Analysis (SPA) to provide a multidimensional and comparative assessment of city health. Using panel data from 2000 to 2020, the analysis covers twenty major cities representing eastern coastal hubs (Shanghai, Guangzhou, Qingdao, Ningbo), central growth poles (Wuhan, Zhengzhou, Changsha, Hefei), and western frontier cities (Chengdu, Chongqing, Lanzhou, Urumqi). Five dimensions—vigor, structural soundness, resilience, ecosystem service maintenance, and environmental loading—are systematically evaluated. Results indicate that coastal cities such as Shanghai, Ningbo, and Guangzhou consistently achieved higher scores due to efficient emergy flows, diversified economic-ecological structures, and stronger resilience to shocks. By contrast, inland cities including Lanzhou, Urumqi, and Zhengzhou exhibited persistent weaknesses, particularly in resource self-sufficiency and environmental impact. The SPA comparison highlights that resilience and ecosystem service functions have grown more decisive over time in distinguishing healthier cities, while vigor and structure remain important secondary factors. Temporal analysis further shows gradual improvement in overall ecosystem health between 2005 and 2015, followed by stagnation or decline in several inland cities after 2016, reflecting the rising costs of environmental stress. Policy insights suggest that differentiated regional strategies—enhancing emergy efficiency in central China, diversifying industrial-resource bases in the west, and reducing ecological loading in high-density coastal areas—are necessary to narrow health disparities and promote sustainable urban trajectories.