Oases are among the most productive and vulnerable ecosystems on drylands as well as central areas of human life and economic development. In China, oasis expansion and degradation are directly related to the survival and development of tens of millions of inhabitants who live within them, profoundly affecting human well-being. However, our understanding of the spatiotemporal dynamics of China’s oases has been limited. This creates a challenge to accurately assess the environmental impacts of oasis dynamics and sustainable oasis development. Here we analyzed Landsat images (5 TM, 7 ETM+, and 8 OIL, ∼61 900 images) over the period 1987–2017, and we produced annual maps of China’s oases (30 m spatial resolution) using trajectories and spectral-temporal segmentation algorithm (LandTrendr) and machine-learning methods (Random Forest). We found that oasis areas increased significantly between 1987 and 2017 (+8.82 Mha). Grasslands and croplands expanded the most, and reclamation of deserts and grasslands made cropland the largest gainer. At the provincial scale, oasis expansion in Inner Mongolia and Qinghai was mainly attributed to grassland restoration. In Xinjiang, Gansu, and Ningxia, reclamation of croplands was also an important factor in addition to grassland restoration. With the expansion of the oasis ∼73.36% of areas showed decreasing trends of soil moisture, and even desertification in some areas. The overexpansion of oases might cause a great challenge to regional water security. Our dataset and results can provide a basis for identifying trade-off areas/regions between development benefits and environmental impacts, helping policymakers to identify high-priority areas for intervention and reasonably plan land-use spatial structure in oasis areas for sustainable development of oases.

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Oases are the most dynamic, productive, and vulnerable ecosystems in drylands and are centers of human life and economic development in arid and semi-arid regions (X. Li et al., 2016;S. Zhou et al., 2015). In China, oases support the livelihoods of tens of millions of inhabitants, and maintaining the stability of oasis ecosystems is essential for regional ecological security and sustainable development (P. Chen et al., 2022a). Under climate change and expanded human activity, China's oases have undergone a significant expansion during the past three decades (P. Chen et al., 2022a), which has profoundly affected regional water budgets and ecosystem services (

Satellite observations since the early 1980s have revealed a trend of “Earth greening” across global terrestrial ecosystems. Dryland vegetation is more sensitive to climate change and human activities. China's drylands are among the largest in extent worldwide, and large-scale ecological restoration of these areas has been implemented since the late 1970s, which has resulted in more complicated but still poorly quantified vegetation dynamics. To figure out the vegetation dynamics and associated driving forces, we provide an assessment of the vegetation dynamics from 1982-2015 using the CO2 fertilization effect function, principal component regression, Residual Trend analysis, and Breaks For Additive Seasonal and Trend methods based on the ERA5 climate factors and GIMMS 3.1 NDVI datasets. This study shows that anthropogenic impacts and CO2 fertilization have jointly led to vegetation greening in China’s drylands since the 1980s, and ecological restoration has accelerated this greening since the 2000s. The results show that the vegetation greening in China’s drylands (41.51% of the study area, +0.60×10-3/yr) is mainly driven by CO2 fertilization (+0.55×10-3/yr) and anthropogenic activities (+0.12×10-3/yr). The anthropogenic effects are especially higher on the Loess Plateau (+1.01×10-3/yr) and the Three-North region (+0.23×10-3/yr). The vegetation dynamics shifts in 6.73% (31.64 Mha) of China’s drylands were directly attributed to anthropogenic impacts around the 2000s. When the anthropogenic effect was intensified, the vegetation dynamics shifted from no change to greening and vice versa, which significantly intensified the vegetation greening since the 1980s. These results capture the processes of ecological programs and provide an assessment of the effects of ecological restoration. This work provides a credible attribution of the vegetation greenness dynamics and trend shifts in China’s drylands, thus facilitating a better understanding of regional environmental change and management.

Ecological restoration (ER) programs play an important role in local and global climate change and carbon management policy interventions. Water resource is a key criterion for assessing the sustainability of ERs. Herein, we explored the spatiotemporal patterns of rainfall interception (RI, an important component of ecosystem water budgets), and its drivers after ER implementation in China. Further, we assessed whether ERs are sustainable by analyzing the trends of RI and water supply. As expected, we found that ERs caused an increase in RI in China from 2001 to 2018 (0.64 mm yr−1, p < 0.01). Changes in the normalized difference vegetation index and leaf area index contributed to a higher change in RI compared with other drivers. The decrease in RI was mainly recorded in the Qinghai–Tibet Plateau in Southwest, northern North, and southern Central and Southern China. Conversely, an increasing trend of RI was recorded in the Loess Plateau in Northwest, Northeast, and East China. Moreover, ERs are not always unsustainable in China, especially in Northeast, East, Central and Southern, and high-latitude regions of northern North China. Even in the Loess Plateau, which was criticized by previous studies, the unsustainability occurred only in the semi-humid region. Future ERs should be prioritized in southern parts of Eastern, Central, and Southern China, and must be appropriately considered in the Northeast and high-latitude regions in North China. It should be alert to the pressures of ERs on water supply, and its demand remains vigilant in the Qinghai–Tibet Plateau and semihumid areas of the Loess Plateau. This study provides new ideas for accurately evaluating the impact of ERs on water security and the sustainability of ERs.