Water-constrained revegetation potential in China’s drylands using a multi-data ensemble approach

Revegetation mitigates climate change through carbon sequestration but intensifies water conflicts between ecosystems and human demands in water-limited regions. This study quantified not only the revegetation potential but also the allowable vegetation conversions in China’s drylands under water constraints using a multi-data ensemble approach. The ensemble estimate of available water resources (AWR) was 65.4±13 mm (median ± SD) in water surplus areas (covering 55% of the region) and −39.1±7 mm in water deficit areas of China’s drylands averaged over 2003–2018. The ensemble of nine precipitation and evapotranspiration data combinations effectively reduced estimation uncertainty compared with most single-dataset combinations. Under current water constraints, the median estimate of gross primary productivity gain associated with revegetation ranged from 4% to 7% across the drylands depending on vegetation types, and 12%–17% in water surplus areas (forests: 14%, grasslands: 17%, both irrigated and rain-fed crops: 12%). Crucially, in water surplus areas, vegetation conversions toward higher water consumption types were feasible. In contrast, in most water deficit areas, the deficit cannot be fully offset by converting existing vegetation to less water-intensive types, suggesting a critical deficit under the current accounting framework. Future revegetation potential will increase with improved water use efficiency and rising AWR under the impacts of climate change. Our research highlights the importance of water constraints on revegetation and the vegetation-specific water costs and carbon benefits, which are critical to implementing natural climate solutions while ensuring water sustainability.