From Carbon–Water Diagnosis to Landscape Optimization: A New Framework for Sustainable Restoration in East Asian Karst

As one of the world’s most extensive and fragile ecosystems, East Asian karst regions are pivotal for carbon sustainability, yet they are exhibiting starkly divergent responses to environmental pressures. While Southwest China has undergone extensive, policy-driven ecological restoration, many parts of the Association of Southeast Asian Nations (ASEAN) region face severe degradation from unregulated agricultural expansion. To understand the underlying drivers of this divergence, this study conducts a comprehensive comparative analysis of the carbon–water trade-offs in these contiguous karst areas from 2000 to 2023. We identify two dominant eco-functional profiles: a “stable carbon sink–moderate water consumption” pattern in Southwest China (15.38% of the area) and a “potentially unstable carbon sink–high water consumption” pattern widespread in ASEAN (24.00%). By integrating the carbon–water risk zoning with MSPA and MCR models, we identified key ecological sources and corridors to map the regional ecological security pattern. The results show high-risk zones (e.g., eastern Myanmar) not only align with fragmented ecological corridors but also exacerbate structural connectivity loss. This approach innovatively links metabolic risks to landscape resilience. Importantly, we found threat drivers differ in the two areas: atmospheric drought (VPD) has become the dominant constraint in ASEAN and soil moisture deficit in the Southwest China. These findings offer a spatially explicit framework for targeted governance and caution against transferring restoration strategies between divergent ecohydrological contexts.