Basin-scale multi-objective optimization and coordination assessment of the water–energy–food–carbon nexus under uncertainty: A Yangtze River Economic Belt case

Amid intensifying global challenges such as climate change, resource scarcity, and population growth, the coupled relationships among water, energy, food, and the environment have garnered increasing attention. The Water-Energy-Food-Carbon Nexus (WEFCN) provides a critical framework for understanding these intricate relationships. However, significant challenges persist in achieving synergistic optimization across multiple provinces and municipalities at the basin scale, addressing resource uncertainties, and enhancing algorithmic adaptability. This study innovatively develops a synergistic optimization and coordination assessment framework for the WEFCN tailored to the Yangtze River Economic Belt basin scale. Integrating life cycle theory and robustness coefficients, while incorporating a self-adaptive multi-objective whale optimization algorithm, the framework generates optimal water and land allocation strategies under scenarios of surface water fluctuations. Additionally, an evaluation framework based on coupling coordination degree is introduced to quantify inter-provincial coordinated development from multidimensional perspectives of fairness, reliability, and synergy. The results demonstrate that optimized allocation reduces irrigation water use while expanding rice cultivation area. Coupling coordination degrees across provinces and municipalities improved, with the comprehensive synergy index increasing by 14%. The proposed framework provides a scientific paradigm and decision-making support for the synergistic optimization and coordination assessment of water and land resources in basin-scale management involving interactions among multiple decision-makers.