Peak greening at moderate shrinking intensity across Chinese counties

As competition among cities increases, shrinkage is increasingly observed in contemporary urban development. However, the systematic, fine-scale ecological impact of shrinkage, particularly on vegetation dynamics, remain poorly characterized. This study identified shrinking and non-shrinking counties in China using nighttime-light data during 2001-2020, examined vegetation growth dynamics using net primary productivity (NPP) validated by normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and leaf area index (LAI), and analyzed influencing mechanisms via XGBoost modelling and SHAP interpretation. We reported three findings: (1) 39.8% of 2891 counties shrank, most severely in Northeast China. (2) Most shrinking counties showed an amplified vegetation greening trend, with median NPP trend (3.43 g C m^-2 yr^-1) 11.7% higher than non-shrinking counties (3.07 g C m^-2 yr^-1). Shrinkage intensity exerted a hump-shaped relationship with NPP trend, peaking at moderate levels, indicating an optimal shrinkage intensity for greening. (3) Differentiated strategies are needed: moderately shrinking counties can amplify gains with passive rewilding; severely shrinking ones need enhanced fiscal transfers for erosion controls and afforestation; non-shrinking collided with an NPP ceiling at ∼20% land conversion, necessitating densification-resistant designs and strict urban-growth boundaries. These findings advance our understanding of social-ecological coupling mechanisms between shrinkage and vegetation dynamics, offer critical insights for developing context-differentiated ecological strategies and enhancing county-level development quality.