Spatio-temporal evolution and driving mechanisms of the Water-Food-Wetland nexus in the Nenjiang River Basin

.With densely distributed wetland ecosystems, the Nenjiang River Basin is a crucial major grain-producing area in China, where water, food, and wetland form a strong nexus. Studying this water-food-wetland (WFW) nexus is of vital significance for the security and synergetic development of multiple resources in the basin. This study constructs a WFW evaluation indicator system covering wetland hydrological service functions and integrates the coordination degree model, structural equation model, and machine learning model to reveal the spatiotemporal evolution and driving mechanism of the WFW nexus in the Nenjiang River Basin. The results show that ① from 1990 to 2020, the WFW nexus coordination degree in the basin evolved from near imbalance to good coordination and near imbalance, with the spatial WFW nexus coordination degrees ranking as upper reaches > middle reaches > lower reaches. ② The water and wetland subsystems in the basin exhibit a synergy effect, while the food subsystem shows significant competition effects with the water and wetland subsystems. Specifically, every 1% increase in food security level decreases water security and wetland ecological security levels by 0.52% and 0.67%, respectively. ③ Agricultural irrigation water consumption is the dominant factor driving the evolution of WFW nexus coordination degree in the basin, with a contribution rate of 35.2%. To maintain the synergistic development of the WFW nexus in the basin, the irrigation water consumption threshold should be 9.86 billion m³. The fierce competition for land and water between grain production and wetland ecological protection proves to be the key factor restricting the synergetic development of the WFW nexus in the basin. These findings can provide reasonable support for devising irrigation agriculture development plans and wetland ecological restoration schemes in the region.