The literature on environmental peacemaking argues that cooperation in the face of shared environmental challenges can facilitate further cooperation, trust building, and eventually peace between states in conflict. Empirical research on environmental peacemaking, predominantly conducted in the form of single case studies, has so far been inconclusive. This article uses a cross-case, multimethod research design to test the environmental peacemaking proposition. More specifically, it argues that the conclusion of a cooperative environmental agreement can have a positive impact on reconciliation between rival states. Based on a new dataset on international rivalry termination, transboundary protected areas, and international freshwater agreements, this article first conducts a statistical analysis and a qualitative comparative analysis (QCA). The results are then verified and refined by six case studies. Triangulation of findings from the three studies suggests that the conclusion of a cooperative environmental agreement facilitates reconciliation in international rivalries. But this effect is contingent on a number of scope conditions, such as high environmental attention, internal political stability, wider patterns or traditions of environmental cooperation, and already ongoing processes of reconciliation. Still, the findings imply that environmental challenges do not only affect peace and security in a negative way. Addressing them jointly also opens opportunities for peacemaking and peacebuilding between states
