Urbanization sustainability under the socio–economic–ecosystem nexus: A city-level emergy assessment of intra-provincial heterogeneity in Shandong, China

China’s rapid urbanization over the past decades has profoundly reshaped its social structure, economic development, and ecosystem integrity. However, previous studies have insufficiently addressed the coupled dynamics among these dimensions, limiting a holistic understanding of urban sustainability. In this study, we adopt an emergy-based perspective to reexamine the urbanization process of Shandong Province (a major economic and industrial hub in eastern China) during 2012–2020, assessing its impacts on the Socio–Economic–Ecosystem Nexus. We find that the Provincial Capital Economic Circle (PCEC) has received increasing policy support and experienced a greater inflow of both local and imported emergy than others. The provincial capital, Jinan, exhibits a clear siphon effect, showing outstanding performance in the economic subsystem, whereas other cities within the PCEC face developmental constraints. The Jiaodong Economic Circle benefits from its coastal advantages and alignment with the Maritime Silk Road policy orientation, leading to a pattern of economy-driven urbanization. Qingdao, in particular, performs strongly in both social and ecological subsystem indicators. To promote balanced regional development, it is essential to enhance policy equity for the Lunan Economic Circle, while strengthening interregional collaboration may offer promising pathways for its future growth. This emergy-based rethinking provides valuable insights for optimizing regional planning and guiding more sustainable urbanization pathways in rapidly developing economies.