While statements by the United Nations Security Council and the Secretary-General demonstrate that environmental degradation is accepted as a possible non-military threat to international peace and security, none of the relevant documentation proceeds to consider how the Security Council might respond to such new threats and sources of instability and conflict. This article examines and evaluates a number of options available to the Security Council should its members choose to address this agenda in more detail. It argues that the UN Charter, international humanitarian law and operational precedent provide an environmental mandate for the Security Council. Any authorization of force, however, is most likely to be confined to environmental war crimes. A more important environmental role for the Security Council lies in preventive diplomacy, conflict resolution and postconflict reconstruction.