The debate over the linkage between security and environment has evolved since 1980s. Whilst the sceptics and advocates have tangled in a discussion on conceptual, political and methodological grounds, the context of the discussion has also evolved simultaneously both as geopolitical events occurred and the research on climate change progressed. The article examines the arguments of different stages of the discussion and explores the innovations in thinking in the early 21st century. It exposes that, whereas the earlier literature was mainly interested in the potential of environmental degradation for causing overt large scale violence, the latest literature has primarily focused on human security and vulnerability as well as the multiple implications of resource wars. It also emphasises the importance of the incorporation of the environmental vulnerabilities into practical policies in order to preserve the humanity’s common habitat and to promote the survival of the poor in the marginal parts of the world.