Quantifying the precipitation supply of China's drylands through moisture recycling

Drylands have a great potential for carbon uptake, yet face a risk of water shortage. Earlier studies have suggested that vegetation restoration in drylands could lead to water loss due to increased evapotranspiration (ET). However, the role of atmospheric moisture recycling in relation between dryland vegetation and precipitation has often been ignored. Here we quantified the contribution of China's drylands to precipitation in local and downwind areas using the state-of-the-art Lagrangian moisture tracking model (UTrack) and satellite datasets. The results showed that drylands contributed 154mm yr⁻¹ of precipitation through moisture recycling within drylands, suggesting a relative contribution and an equivalent precipitation recycling ratio (PRR) of 22%. On average, northern China received the largest precipitation from drylands moisture recycling, followed by northeastern, northwestern, southwestern, eastern, and southern China. The precipitation contribution from dryland ecosystems mainly concentrated in the growing season (132mm yr⁻¹), accounting for 88% of the yearly contribution. Moreover, we observed that vegetation transpiration dominated the moisture effect (i.e., P_T occupies 69% of total P_ET). During 2001-2020, the enhanced moisture recycling brought about 7mm decade⁻¹ of precipitation within drylands, offsetting 37% of the increasing ET (19mm decade⁻¹). This suggests an overestimation of water consumption by vegetation restoration in drylands if disregarding the contribution from vegetation-sourced moisture recycling. Overall, our study highlights the importance of atmospheric water recycling on precipitation supply in drylands, which is crucial in guiding ecological restoration projects for carbon peak and carbon neutrality targets, as well as sustainable management of water resources in water-scarce drylands.