The degradation and marginal effects of green space under the stress of urban sprawl in the metropolitan area

Urbanization has created economic and social opportunities, but the escalating conflict between urban development and green space adversely affects human well-being. The encroachment of urban sprawl on green spaces and the resulting ecological issues have gained widespread global attention. However, existing research has focused on the correlation between urban sprawl and green space characteristics at a singular scale. This paper identified degradation types of green spaces based on their multidimensional feature indicators between 2005 and 2020. Specifically, ten indicators describing urban sprawl were selected. Key factors and their stress effects were identified using Gradient Boosting Regression Trees (GBRT) and Shapley additive explanations (SHAP) models in different clusters. The results reveal that the degradation of green spaces in Shanghai is categorized into five types. The key stress factors for green spaces include indicators of urban sprawl intensity, pattern indicators, and socio-economic indicators. All key factors exhibited significant marginal effects, and their corresponding thresholds were identified. Furthermore, there was evident spatial differentiation in the stress effects. The findings can serve as a valuable foundation for urban managers in formulating sustainable land policies, facilitating the enhancement of green space quality and sustainable development. •The degradation of green spaces in Shanghai has five types.•The key factors of stress effects and their marginal effects and thresholds are identified.•Stress effects have spatial differentiation.