Transboundary conflict from surface water scarcity under climate change.

Transboundary river basins (TRBs) are at risk of water scarcity-induced conflicts, especially given the rising water demand and impacts of climate change. Despite extensive efforts and some progress, the mechanisms linking water scarcity to conflicts in TRBs remain insufficiently understood, and identifying effective mitigation and adaptation strategies remains a challenge. In this study, we introduce a framework for predicting TRBs vulnerable to water scarcity-induced conflicts, based on the concept of water dependency, defined by monthly water scarcity. This framework successfully explains over 80% of the TRBs experiencing water scarcity-induced conflicts during 2005-2014. Our projections indicate that, without mitigation and adaptation measures, nearly 40% of global TRBs could face potential conflicts driven by water scarcity in 2041-2050, with hotspots in Africa, southern and central Asia, the Middle East, and North America. However, proactive measures such as intra-basin cooperation could reduce this proportion to less than 10%. This study underscores the urgency of increased investment and active stakeholder engagement to foster intra-basin cooperation and avert potential conflicts.