Whilst the human cost of war is profound and undisputed, war’s environmental consequences have received far less attention, despite their potential for significant and long-term harm to human health and ecosystems. This edition of the environmental SCIENTIST examines the environmental dimensions of conflicts: how the environment can be affected by armed conflicts and military activities, and what can be done to increase its protection. Read about how citizen science could help to protect people and ecosystems, why deforestation rates can soar after the fighting has stopped, and the promise and perils of protected zones.