Research on the nonlinear mechanism and multi-scale adaptive strategies of ecosystem services in the Zhengzhou metropolitan area from the perspective of water-carbon-food-ecology nexus

Uncovering the multiscale effects and nonlinear response mechanisms of ecosystem services (ESs) within the water‑carbon-food-ecology (WCFE) nexus, and developing differentiated regional governance strategies, is crucial for reconciling the conflict between conservation and development in rapidly urbanizing regions and for implementing the United Nations Sustainable Development Goals (SDGs). Addressing the limitations of existing studies—such as insufficient accuracy in identifying nonlinear thresholds at the metropolitan scale and the lack of multiscale adaptive management strategies—this study takes the Zhengzhou Metropolitan Area (ZZMA) as its research subject. Based on multi-source spatiotemporal data from 2000 to 2023, we established a research framework comprising “spatiotemporal evolution—mechanism diagnosis—zonal regulation.” First, the study reveals the spatiotemporal differentiation characteristics of Comprehensive Ecosystem Services (CES) at both the county and 1 km grid scales. Second, it introduces the XGBoost-SHAP-PDP interpretable machine learning model to analyze the nonlinear response characteristics and threshold effects of driving factors. Finally, it couples the results of mechanism analysis with Self-Organizing Maps (SOM) to construct a dual-scale adaptive zoning management framework. The results indicate: (1) During the study period, CES exhibited a spatial pattern characterized by “ecological carbon sequestration dominated by western mountainous areas and water and grain security supported by central and eastern plains,” and underwent a phased evolution of “fluctuating decline followed by localized recovery”; (2) Natural endowments and human activities jointly drove the spatial differentiation of CES, with the proportion of construction land serving as the core driving factor and its contribution continuously increasing; the contribution of factor interactions was significantly higher than that of individual factors; (3) A significant nonlinear relationship exists between CES and key driving factors, exhibiting dynamic evolution in terms of interaction modes, threshold effects, and impact intensity; (4) Based on the identification of dual-scale service clusters, ecological adaptive management units were precisely delineated, and a differentiated management strategy that balances ecological bottom lines with development was proposed by integrating Nature-based Solutions (NbS) principles. This study aims to bridge the gap between a deep understanding of the underlying mechanisms of ESs in rapidly urbanizing regions and their effective, multi-scale adaptive management, thereby providing scientific support for regional resource coordination, green transformation, and high-quality development.