Whether the enhanced terrestrial vegetation carbon sink affect the water resources in the middle-low latitude karst areas of China?

To meet the carbon peak and carbon neutrality objectives, the middle-low latitude karst areas of Southwest China have become popular research areas due to their rich terrestrial carbon sink storage capability. However, whether the enhanced terrestrial vegetation carbon sink will consume more water resources in this area is still unclear. In this research, three mid-small basins that represent different levels of carbon sink and human activity were selected in the middle-low latitude karst area of Southwest China. Net ecosystem productivity (NEP) was used to indicate the variation in the carbon sink, and the remote sensing-driven distributed time-variant gain model (RS-DTVGM) and a new runoff monitoring technology named the remote sensing hydrological station (RSHS) were integrated to quantitatively analyze the correlation between the carbon sink and water resources from 2000 to 2020. The results showed that 1) in the past 20 years, the NEP of the three basins all showed a trend of first increasing and then decreasing, while the runoff of all basins showed a trend of first decreasing and then increasing. The opposite trends of NEP and runoff supported the negative correlation between NEP and runoff. 2) The enhanced carbon sink will consume more water, but on the premise of similar climatic and geographical conditions, the significant strong negative correlation between the carbon sink and water resources will gradually weaken and become insignificant as the land use/cover change (LUCC) occurs and the forest background conditions improve from approximately 35% to more than 80%. 3) The serious drought event had a large influence on the water yield and carbon sink, and the basin with higher forest coverage could resist extreme drought by consuming more runoff to retain more carbon. This research quantitatively answered the question of whether the enhanced carbon sink will consume more water resources in the middle-low latitude humid karst areas, which provide valuable implications to managers who want to increase carbon sinks but worry about lost water resources, and the results can be used to promote the co-evolution of the water-carbon system, thereby achieving the carbon neutrality objective.