This study explores the interaction mechanisms between population and environment systems within the context of high-quality development (HQD), providing empirical insights for developing countries navigating rapid urbanization. The existing literature often focuses on regional macro-averages, which may obscure internal spatial structural heterogeneity and the phenomenon of bottleneck shifts within urban agglomerations (UAs). Focusing on six typical UAs in China from 2011 to 2023, we constructed a multi-dimensional evaluation system and utilized an optimal parameters-based geographical detector (OPGD) and an obstacle degree model (ODM) to decode the spatiotemporal evolution of these systems. The results demonstrate that: (1) Both population and environment subsystems have improved steadily. Ecological carrying capacity has increased significantly, and the primary systemic constraint has transitioned from the “environmental bottom line” to the “population dividend,” with several super/mega cities converging toward a synchronous development interval. (2) The modified coupling coordination degree (MCCD) exhibits an overall upward trend. While eastern UAs demonstrate core-driven synergistic evolution, central and western UAs face risks of a “single-core siphon effect” and “peripheral hollowing-out,” leading to pronounced spatial polarization. (3) The OPGD analysis reveals that the driving efficiency of large-scale traditional infrastructure investment has experienced a marginal decline, whereas economic fundamentals and technological innovation have emerged as core drivers for non-linear enhancement. (4) The ODM confirms that traditional environmental pressures have been substantially alleviated. The core constraints have transitioned to the population and economic dimensions, with labor productivity and science and technology (S&T) expenditure identified as the primary obstacles. Aligning with the United Nations Sustainable Development Goals (SDGs), our findings may suggest that policy focus should shift from physical spatial expansion toward “soft connectivity” based on institutional and technological spillovers. We recommend establishing cross-regional coordination mechanisms to mitigate the siphon effects of core cities and transitioning policy priorities from ecological defense to high-quality population development.
Liu et al. (Tue,) studied this question.