How water–energy–food services and their interactions change along multiple environmental gradients

With climate change and ongoing socioeconomic development, issues related to water, energy, and food security are becoming more pressing, threatening human well-being. Under the influence of environmental factors, water–energy–food resources exhibit significant spatial heterogeneity. However, limited information exists on how water–energy–food services and their interactions respond to various environmental gradients. Using the Songhua River Basin as a case study, this study quantified the spatiotemporal variation and interaction between water–energy–food services (water yield, net primary productivity, and food production) from 2001 to 2020, investigated changes in water–energy–food services and their interactions with each environmental gradient (elevation, precipitation, temperature, and vegetation cover) using a generalized additive model, and explored the underlying mechanism of interactions between water–energy–food services under different environmental gradients based on a structural equation model. The results indicated that water, energy, and food services increased significantly (p < 0.01) by 4.33 mm/yr, 4.09 gC/m2·yr, and 0.06 t/ha·yr, respectively. A trade-off between water–energy services was observed in 12.36 % of the southern regions. Water–energy–food services exhibited distinct nonlinear changes with multiple environmental gradients, with several key threshold inflection points identified. As elevation and precipitation increased, the synergy between water–energy services weakened, shifted to a trade-off, and then strengthened. Human activities contributed to water–food services but restricted energy services. Photosynthesis, evapotranspiration, and vegetation cover were identified as the main factors influencing the interactions between water, energy, and food services, driven by competitive relationships under different environmental gradients. This study provides a significant basis for ecosystem management strategies under various environmental gradients.