Dissecting the Characteristics and Driver Factors on Global Water Use Efficiency Using GLASS Data Sets

Ecosystem water use efficiency (WUE) is a crucial parameter for understanding the interaction between carbon and water cycles. However, the spatio–temporal evolution and drivers of WUE remain unclear. This study utilized global annual scale global land surface satellite gross primary productivity and evapotranspiration data from 1982 to 2018 to estimate WUE and analyze its spatio–temporal characteristics. Additionally, the study investigated the response of WUE changes to five environmental factors (precipitation [PRE], soil moisture, temperature [TEM], palmer drought severity index, and vapor pressure deficit [VPD]) on WUE changes using partial correlation and structural equation modeling. The results suggested that the global annual WUE increased markedly over the study period, at an average rate of 0.0016 gC m−2 mm−1 H2O year−1. In contrast to the existing knowledge on the drivers of WUE change, climate change was found to have a larger contribution to WUE changes at the global and regional scales, especially in terms of TEM and VPD. A positive correlation between TEM and WUE was observed, but extreme TEM could lead to a decrease in WUE. VPD had the most significant direct effect on WUE, and its negative effect offset the positive influence of TEM especially in hyper‐arid, semi‐arid, and arid regions. These findings offer new insights into the impact of VPD and global warming on WUE. Plain Language Summary Water use efficiency (WUE), defined as the ratio of gross primary productivity to evapotranspiration, is one of the key indicators for measuring the carbon‐water coupling in ecosystems. Analyzing the temporal and spatial evolution of global WUE and its influencing factors can offer valuable insights into addressing the challenges posed by global climate change. In this study, we examined the spatio‐temporal dynamics of global WUE over an extensive time span and utilized structural equation modeling to identify the primary drivers of WUE variation. Our findings reveal a consistent increasing trend in annual global WUE from 1982 to 2018, with an average annual increase of 0.0016 gC m−2 mm−1 H2O. Temperature and vapor pressure deficit (VPD) emerged as the key drivers of WUE changes, with the positive effect of temperature on WUE being counteracted by its negative influence through VPD (approximately 75%). This research contributes to our understanding of how climate change impacts carbon and water cycles within ecosystems and lays a foundation for enhanc