Global vegetation has undergone sustained greening since the 1980s, profoundly reshaping terrestrial carbon and water cycles. However, whether greening consistently enhances or depletes regional water availability (WA) remains a subject of intense debate with strong regional dependencies. Moreover, the spatiotemporal dynamics of carbon–water coupling strength and the climatic mechanisms governing its evolution across historical and future scenarios have not been systematically quantified at the global scale. Here, we systematically investigated this question across aridity gradients and vegetation functional types by integrating multisource satellite data with CMIP6 multimodel ensemble projections and applying contribution partitioning, moving-window correlation and trend analysis, and ridge regression. Our results showed that the global leaf area index (LAI) exhibited continuous growth during both the historical period (1982–2023) and the future scenario (2024–2100), while WA shifted from a historical decline to a future increase. Spatially, humid regions contributed the most to LAI and WA trend changes, with forests showing the most pronounced greening among the vegetation functional types. During the historical period, greening-associated drying (GAD) dominated (48.6%), but under future scenarios, greening-associated wetting (GAW) expanded substantially to 68.3%. Carbon‒water coupling analysis revealed that despite variations across aridity gradients and vegetation types, the global coupling trend had continuously weakened over the past four decades and was projected to persist on this trajectory under future scenarios. Decomposition of driving factors indicated that temperature (TEM) was the dominant driver of carbon‒water coupling. In arid and semiarid regions, vapor pressure deficit (VPD) dominated, while semi-humid regions were jointly regulated by TEM, VPD, and soil moisture. Humid regions were primarily controlled by TEM. Furthermore, different vegetation functional types exhibited distinct response mechanisms to climatic drivers. This study provides new insights into the spatiotemporal evolution of vegetation carbon‒water coupling and its climatic driving mechanisms, with important implications for predicting future ecosystem changes.
Wang et al. (Thu,) studied this question.