Bundling regions to explore synergies and trade-offs among water-wetland-food nexus in Black Soil Granary, China

The China’s Black Soil Granary (CBSG) is vital for national food security in China. Large-scale agricultural reclamation has boosted grain production, however, it has led to the encroachment and shrinkage of wetlands, disrupted the sustainability of water resource and threatened the stability of grain production. Therefore, evaluating the water-wetland-food (WWF) nexus is crucial for balancing agriculture and wetland ecosystems. However, quantifying synergies and trade-offs within the WWF nexus remains challenging due to unclear mechanisms. In this study, a comprehensive WWF evaluation system was proposed to analyze spatiotemporal patterns across 20 prefecture-level cities (2000–2020) using a coupling coordination degree model. Cities were classified into four distinct WWF bundles based on a similar index. The Partial Least Squares Structural Equation Modeling (PLS-SEM) and Redundancy Analysis (RDA) were employed to explore internal and external drivers of changes in the WWF nexus. The Results show that: (1) From 2000–2020, the WWF system transitioned from a wetland-dominated Barely Coordinated bundle to a WWF Intermediate Coordinated Development bundle, indicating progress toward intermediate coordination (0.7–0.79). (2) Increased precipitation positively impacted wetlands through water resources, but rising food security indices compromised wetland security, hindering WWF synergy. (3) External factors, such a precipitation intensity, GDP per capita, NDVI, and urbanization, positively influenced WWF development. (4) Water resources are the core constraints, wetlands ensure sustainability, and food security is the central goal. This study identifies the conflicts between water and ecology within WWF bundles, provides targeted actions for sustainable development, and promotes regional collaboration.