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Large-scale afforestation is a common measure to control desertification and soil erosion, especially in China. However, the massive afforestation may consume excessive water resources and cause the severe water shortage in the arid and semiarid regions. To understand the water consumption characteristics of afforestation, this study identifies the afforestation area and chooses the Water Footprint (WF) and Ecological Water Deficit (EWD) as the indicators to assess its water consumption, taking the Inner Mongolia as the typical arid and semiarid study area. The results showed that afforestation area in Inner Mongolia increased by 38,397.38 km2 and NDVI presented a rising trend during 2000–2015. The afforestation WF increased from east to west in Inner Mongolia, with a maximum difference of 268.02 mm. Due to the difference distribution of precipitation, the afforestation EWD ranging from 74.6 mm to 609.9 mm which indicated that afforestation has suffered from different degrees of water shortage in Inner Mongolia. In the long term, afforestation might exacerbate the water shortage and soil erosion in Inner Mongolia. Therefore, afforestation should take full account of local water conditions, and government should seek other ways such as conserve natural vegetation to make the restoration more sustainable. • The afforestation area was identified in Inner Mongolia from 2000 to 2015. • The Water Footprint (WF) and Ecological Water Deficit (EWD) of afforestation were calculated for the study area. • The afforestation WF increased from eastern to western Inner Mongolia, showing variation with the precipitation. • All afforestation areas suffered from water deficit ranging from 14.45 mm to 608.90 mm, increasing the groundwater pressure. [ABSTRACT FROM AUTHOR]

As a vital solution for combating the environmental degradation, afforestation has been widely implemented in arid and semi-arid areas. However, some negative effects have also occurred, due to the lack of regional water resources. Besides, with the impact of climate change, water scarcity in these areas is likely to get worse in the future. In this study, the water resources supply-demand pressure of afforestation under different future scenarios in Inner Mongolia was investigated. Landtrendr method was used to detect the increased vegetation area from 2000 to 2020, and the afforestation area was identified by overlapping analysis combined with the land cover data. The water stress index (WSI) was employed to analyze the water pressure of afforestation area. The results revealed four major findings. (1) During 2000–2020, the accumulated afforestation in Inner Mongolia was 71410 km2, and the shrubs accounted for 86% of the total area of afforestation; (2) The afforestation water stress index showed a significant upward trend with mean values of 0.55, 0.59 and 0.61 under RCP 2.6, 4.5 and 8.5 scenarios, respectively; (3) The overall water resources supply-demand pressure of afforestation in the western region was greater than that in the eastern of Inner Mongolia. (4) In the future, measures need to be taken to alleviate the pressure of water resources on the afforestation in western Inner Mongolia. These findings could help us figure out the afforestation water stress under the climate change and provide the reference to adopt reasonable afforestation management strategies. • Afforestation area increased by 71410 km2 in Inner Mongolia, from 2000 to 2020. • The afforestation water resources pressure was higher in western Inner Mongolia. • The water resources supply-demand pressure increased with higher CO 2 emissions. [ABSTRACT FROM AUTHOR]