Complex climate effects on cooperation and disputes in transboundary river basins

A growing body of evidence suggests a link between climate and conflict. In contrast, the link between climate and cooperation remains much less investigated, although it has been studied in the context of transboundary river basins. Even for transboundary waters, however, earlier results have not decisively answered whether the effect of climate on conflict or on cooperation is stronger. Here we concurrently investigate both cooperation and conflict in transboundary river basins across the world as two potential responses to changes in climatic factors. Our results indicate that one-standard deviation changes in climate variables affect cooperation more than conflict in absolute terms, although effects on conflict are large in relative terms. Furthermore, lower water availability is associated with worse outcomes both through fewer cooperation events and more frequent conflicts. While higher temperatures are associated with more frequent cooperation, the projected decrease in precipitation and soil moisture projected for many regions of the globe may offset positive effects of temperature, and reinforcing cooperative activities should therefore be a policy priority. It is clear that including a full set of potential responses - positive, negative and none - are needed to understand the climatic influence on regional human cooperation and conflict. We encourage further studies that investigate such full-spectrum effects also for other situations than transboundary river basins.