China’s deserts greening and response to climate variability and human activities

about oasis expansion and sand stabilization measures as the two major factors of desert green- ing in China’s deserts are listed in the Supplementary Materials. Discussion Variations in the NDVI and its relationship with the climatic factors China’s deserts showed significant greening trends both temporally and spatially, reflecting the increased vegetation cover of China’s deserts during the study period. Desert greening has far-reaching impacts on climate variability and environmental improvement. Firstly, it increases the land space available for human use, and the increased vegetation cover in deserts increases the carbon sink capacity. Secondly, increased vegetation helps improve the water cycle and increases local air humidity, thus improving the global climate [69,70]. In addition, it also reduces dust storm weather in northern China and improves air quality [71,72]. In a similar period, greening was observed not only in the China’s deserts, but also in other arid and semiarid regions [19]. For example, a slight increase was observed in more than 80% of the arid mountain-oasis river basin in northwestern China [73]. In the Hexi region, approxi- mately 70% of the vegetation area presented a significant increasing trend, and only 2.85% pre- sented a significant decreasing trend [74,75]. And a significant increasing trend of the NDVI was observed in Xinjiang [76]. In general, precipitation has been shown to be the main cause of NDVI rise in arid and semiarid regions, such as the Hexi region, Xinjiang, and Central Asia

[34,73,75,76]. However, from this study, although the correlation between precipitation and NDVI was significant on the annual scale, the area with significant correlation was only 15.14%. The positive effect of precipitation and the negative effect of temperature on NDVI, Fig 7. Greening regions caused by human activities. Green areas denote desert regions where greening trends were influenced by human activities. https://doi.org/10.1371/journal.pone.0256462.g007 PLOS ONE China’s deserts greening and response to climate variability and human activities PLOS ONE | https://doi.org/10.1371/journal.pone.0256462 August 30, 2021 13 / 20