This thought-provoking book explores how the global ecological crisis profoundly challenges conventional meanings of environmental security and raises important questions about how states and other institutions now face the future.Simon Dalby provides unique insights into the traditional search for security in terms of using firepower to dominate states and environments, and how this is now endangering people across the globe. Whereas earlier concerns about nuclear firepower focused on the security dilemmas it posed, Dalby offers a new perspective into the existential threats to civilization presented by the combustion of fossil fuels. Propounding that the constraint of firepower in both senses is now key to a flourishing human future, the book calls for international relations scholars to rethink many of the central premises in the field and formulate new policies that focus on the necessity of ecological flourishing to provide meaningful security in a climate disrupted world.Visionary and inspiring, Rethinking Environmental Security will be a critical read for scholars and students of international relations, climate change, environmental governance and regulation, and political geography and geopolitics. Its novel ideas will also be beneficial for policy makers and practitioners in these fields.