Evaluation of the Coupling Coordination Degree Between PM2.5 and Urbanization Level: A Case in Guangdong Province(2000–2021)

Rapid urbanization creates a conflict between economic prosperity and human health, a tension largely stemming from deteriorating urban air quality. For fast-growing megacities, achieving a sustainable balance—where urban ecosystems support both development and well-being—is a major challenge. This study quantitatively explores pathways to sustainability in Guangdong Province, China, by analyzing the spatiotemporal coupling between urbanization intensity and PM₂.₅ pollution from 2000 to 2021.

We developed a comprehensive urbanization index using 19 socioeconomic indicators, validated against long-term Nighttime Light (NTL) remote sensing data. To assess progress toward sustainability, we applied the Coupling Coordination Degree (CCD) model and tested the Environmental Kuznets Curve (EKC) hypothesis across three dimensions: land expansion, population growth, and economic development.

Our analysis identifies a pivotal turning point in 2010. Before this threshold, rapid urban expansion significantly degraded air quality, with urbanization and pollution increasing synchronously. After 2010, however, the region underwent a distinct transition—shifting from "Discordance" to "Transitional" and finally to "Advanced Coordination." For public health, these changes are substantial: PM₂.₅ concentrations fell by 49.3% from their peak, and annual haze days in core cities like Guangzhou dropped by over 89% (from 36.8 to 4 days). This trend effectively decouples pollution from economic growth. Spatially, our findings highlight a clear divide: coastal urban agglomerations (e.g., Pearl River Delta) have achieved high coordination through industrial upgrading and strict regulations, while inland areas still grapple with aligning development with environmental quality.

These results provide empirical evidence that targeted policy interventions—including China’s Air Pollution Prevention and Control Action Plan—can reverse the adverse health impacts of urbanization. We demonstrate that the Coupling Coordination Degree is a vital tool for policymakers to monitor the shift from conflict to synergy, ensuring that future urban ecosystems prioritize human well-being alongside economic growth.