Decreased ecosystem stability during the expansion and greening of East Asian oases in the early 21 st century

Abstract In arid and semi-arid regions, oases function as critical socio-ecological systems. East Asia, particularly China and Mongolia, contains some of the world’s most densely concentrated oasis ecosystems. Since the early 21st century, oases in this area have expanded substantially with widespread vegetation greening. However, it remains unclear whether this notable expansion and greening reflect genuine improvements in ecosystem resilience or mask emerging vulnerabilities under limited water availability. Here, we quantified greening status and resilience dynamics of oases in East Asia from 2000 to 2020 using remote sensing time series. We developed a joint-threshold assessment framework to evaluate current stability state of vegetation in East Asian oases under water-constrained conditions. Results indicate that while East Asian oases exhibit overall expansion and greening trends, these improvements have not concurrently translated into enhanced regional ecosystem stability. Moreover, according to this framework, only 17% of all oases are classified as ‘sustainable’ in East Asia under current water-availability conditions, and a majority of the recently expanded oases are biased toward transitional states, indicating that these oases may be fragile under future water constraints. Overall, our study provides an operational diagnostic basis for prioritizing water-allocation strategies in the sustainable management of oases in arid and semiarid areas, as the apparent surface greening and vegetation expansion may coincide with accumulating hydrological unsustainability and elevated degradation risk.