0123456789();: Drylands comprise about 41% of Earth’s land surface and support more than 38% of its population (>2 × 10 9 people), approximately 90% of whom are in low and middle-income countries 1,2 . Dryland ecosystems pro- vide a wide range of important services including water, food, energy, fibre, carbon sequestration, habitat, bio- diversity and recreation 3,4 . However, these ecosystems are considered fragile 5,6 and sensitive to desertification 7,8 . Widely reported aridity increases attributed to anthro- pogenic climate change 9,10 would cause a serious decline in ecological security 11 , alongside negative ecological consequences such as soil moisture limitation and biogeochemical cycle disruption 12 . These changes are inconsistent with observed increases in greenness over many drylands 13,14 . These conflicting findings high- light the complexity of desertification processes 15 , and emphasize the pressing need to improve understanding of how active dryland processes will be altered in the near future 16 . Drylands are regions where the aridity index is below 0.65 (REF. 17 ). There are four dryland subtypes defined by the aridity index: hyper-arid (aridity index < 0.05), arid (0.05 ≤ aridity index < 0.20), semi-arid (0.20 ≤ arid- ity index < 0.50) and dry sub- humid (0.50 ≤ aridity index < 0.65). Based on this definition, China has one of the largest dryland areas worldwide (6.6 million km 2 ) 18 , which supports various ecosystems (FIG. 1a) and 12 main deserts (FIG. 1b) that provide goods and services to 580 million people living in these areas. These drylands are characterized by low and highly variable annual precipitation and high potential evapotranspiration 19,20 , coarse-textured, nutrient-poor soils 21 and sparse veg- etation with low annual productivity 22,23 . The struc- ture and functioning of dryland ecosystems in China involve complex, dynamic, interacting processes that are both spatially and temporally variable, and influenced by numerous factors that strongly affect their ability to provide ecosystem goods and services (Supplementary Fig. 1). Water is the main limiting factor and principal driver of plant biodiversity and ecosys- tem functioning 24,25 . Moreover, hydrological services (for instance, water supply) are the basis for realizing other services such as soil generation, carbon seques- tration and recreation 26 . However, desertification (FIG. 1c) increases the challenges related to water supply, food security and reductions in the ecosystem carbon pool 27,28 . China’s drylands are seriously threatened by desertification 29 , which is the outcome of coupled Desertification A type of land degradation in drylands induced by climatic variations and human activities. Ecological security The capability of an ecosystem to maintain its stability under external stress. Drivers and impacts of changes in China’s drylands Changjia Li 1,2 , Bojie Fu 1,2 ✉ , Shuai Wang 1,2 , Lindsay C. Stringer 3 , Yaping Wang 1,2 , Zidong Li 1,2 , Yanxu Liu 1,2 and Wenxin Zhou 1,2 Abstract | China has 6.6 million km 2 of drylands that support approximately 580 million people. These drylands are at risk of desertification. In this Review, the changes observed in China’s drylands are synthesized, with a focus on their drivers and the effects of 13 large-scale land conservation and restoration programmes aimed at mitigating them, including the Three-North Shelterbelt Development Program and Grain for Green Program. After the implementation of the first large-scale restoration programme in 1978, 45.76% of China’s drylands experienced statistically significant land improvement or vegetation greenness, as identified by the Normalized Difference Vegetation Index. However, activities associated with restoration and conservation projects, such as afforestation, also impose substantial water pressure. Desertification thus remained prevalent during 1980–2015, with 11.43% drylands (especially in north-eastern and north-western drylands) experiencing land degradation or vegetation brownness. Drylands remain at risk of expansion owing to increasing aridity, particularly in semi-arid areas. Future trade-offs between the effects of CO 2 fertilization and increased aridity on dryland vegetation cover are still poorly understood. Long-term experiments on the interactions between physical–chemical–biological processes across spatial and temporal scales, such as large-scale field surveys using standardized protocols, are needed to better manage drylands in China and globally. 1 State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, China. 2 Institute of Land Surface System and Sustainable Development, Faculty of Geographical Science, Beijing Normal University, Beijing, China. 3 Department of Environment and Geography, University of York, York, UK. ✉ e-mail: bfu@rcees.ac.cn https://doi.org/10.1038/ s43017-021-00226-z REVIEWS NATURE REVIEWS | EARTH & ENVIRONMENT