Climate change dominates variations in water fluxes and availability than tree restoration and their interactions

Large-scale tree cover expansion has been widely recognized for increasing evapotranspiration (ET) and reducing streamflow if other factors, such as climate change and atmospheric moisture cycling (AMC), are not taken into consideration. However, it remains unclear on the specific and relative contributions of climate change, tree restoration (TR), and AMC to changes in water fluxes and availability which may mislead water resources conservation and management. In this study, we quantitatively assessed the separated impacts of 67.2 million ha of tree restoration in China (Scenario 1) and the integrated effects of climate change and tree-restoration potential (Scenario 2) on the changes in evaporation ( E ), precipitation ( P ), and streamflow ( Q ), with and without AMC. Budyko-based hydrological models and the UTrack atmospheric moisture transport dataset were employed for this purpose. Taking China as a case, the results show that climate change, tree restoration, and AMC contribute 63.56%, 35.75, and 0.69% to E increase in China, 63.29%, 36.17%, and 0.53% to streamflow decrease in areas with precipitation decrease in China, respectively. Tree restoration would result in 22.67 mm·yr ^− 1 reduction in China’s streamflow on average; while, the increase in precipitation induced by climate change and AMC lead to a 3.28 mm·yr ^− 1 increase in streamflow, ultimately shifting the decrease in streamflow from 22.67 to 19.39 mm·yr ^− 1 . The spatial distribution patterns of the increase and decrease in streamflow are consistent with these of precipitation changes. These findings highlight the dominant effects of climate change on hydrological fluxes and availability, and the significance of integrating climate change into sustainable water resources conservation and management.