Regulating effects and impact mechanisms of ecosystem regulating services on air quality: Evidence from the Yangtze River Economic Belt, China

Air quality, increasingly threatened by global climate change and human activities, critically impacts human well-being (HWB). While ecosystem services, benefits humans derive from natural ecosystems, are known to support HWB, the specific regulatory effects of ecosystem regulating services (ERS) on air quality remain unclear. Taking Yangtze River Economic Belt (YREB) as a case, this study addresses this gap by introducing the air quality-ERS coordination index (AECI) to quantify the regulating effects of ERS on air quality. Coupling degree models, random forest regression, Shapley additive explanations, and accumulated local effects models were employed to examine the spatio-temporal heterogeneity and mechanisms influencing ERS regulating effects. The findings indicate that: (1) From 2000 to 2020, ERS in the YREB declined erratically, while air quality initially worsened but improved after 2013, influenced by China's air quality policies. (2) Analysis was divided into natural development (2000−2013) and policy intervention (2013−2020) periods, with ERS closely linked to air quality in both. (3) During policy intervention period, AECI values were 7.9 times higher than in natural development period. Along the urban development gradient, AECI increased in natural development period but decreased in policy intervention period, showing marked core-edge heterogeneity. Core cities exhibited the highest AECI in policy intervention period, indicating stronger policy responsiveness. (4) Population density, temperature, and land surface temperature were dominant factors influencing ERS regulating effects on air quality, with varying impacts across periods. This study enhances the understanding of ERS-air quality interactions and provides a scientific basis for future research and policy formulation.