Vegetation restoration dominated the variation of water use efficiency in China

• GPP and WUE of China generated a significant increasing trend during 2000–2017. • GPP contributed more to WUE variation than ET in China. • Vegetation greening caused by ecological restoration project dominated the increased WUE in China. Implementation of numerous ecological restoration programs over the last two decades has significantly increased vegetation coverage in China. However, the response of the coupled carbon and water cycles to the large-scale vegetation restoration and the underlying mechanisms remain unclear. This study analyzed the spatiotemporal patterns of regional gross primary productivity (GPP), evapotranspiration (ET) and water use efficiency (WUE) in China using the two-leaf light use efficiency (TL-LUE) and the Priestley Taylor Jet Propulsion Laboratory (PT-JPL) models during the 2000–2017 period. The influencing mechanisms of anthropogenic re-vegetation and climatic factors on regional WUE were also analyzed. Results indicate that (1) both the GPP and WUE showed a significant increasing tendency with inter-annual change rates of 10.53 g C m −2 yr −1 and 0.01 g C kg −1 H 2 O yr −1 , respectively; while the inter-annual change rate of annual ET was 1.43 kg H 2 O m −2 yr −1 . (2) Spatially, the regional GPP dominated WUE variation of more than 79.51% of the total area. (3) Among the influencing factors, the greening of vegetation driven by human activities (LAI h ) explained 35.27% of the WUE variation in China, much more than the climatic factors over during the study period. At the regional scale, human-driven vegetation greening also dominated the increasing WUE at regional scale. These findings provide important information to support large-scale ecological restoration policy/decision making to improve ecosystem services in China.