Threats to and from ‘the environment’ inform geographical depictions of danger with widespread reach in political and policy circles. These fears invoke an existential anxiety about collapsing conditions of life – from ‘dangerous climate change’, and species extinctions to fossil fuel depletion and global water shortages. The ‘securitisation’ of socio-environmental processes is at once both a consequence and driver of such concerns, prescribing urgent, even emergency, measures to prevent serious harm. Against this tendency, the papers in this themed section critically interrogate the application of securitising moves to a series of perceived environmental threats – moves which mark out spaces of safety in terms of ‘climate security’, ‘water security’, ‘food security’ and ‘energy security’. Theoretically, the papers serve as a productive foil to the dominant strand of securitisation theory associated with the so-called Copenhagen School. There has been relatively little interrogation by geographers of this approach, despite its strong spatial assumptions: the Copenhagen School posits state-bounded territoriality as the foremost arena of security dynamics, and advances explanatory claims about the conditions and scope for securitisation of the environment. Two featured papers argue that the Copenhagen School perspective on environmental security misses important spatialities of geopolitical power, while two more explore other modes of securitisation – disciplinary, biopolitical and geo-economic – neglected by this approach. For critical geographers the research challenge is, we argue, to capture the distinctive trajectories of securitisation attached to environmental danger, demonstrating that their effects more often than not foreclose rather than protect human freedom and dignity.