Despite the current environmental crises of anthropogenic climate change and environmental degradation afflicting the world, dualisms of culture/nature, human/non-human and animate/inanimate sustain a perspective on ‘the environment’ in which the human and the cultural are privileged over the natural world and other species. Policies on ‘sustainable development’ are likewise predicated upon efforts to assure future human prosperity. Our objective in this paper is to establish an alternative, post-anthropocentric perspective on environmental sustainability. Drawing on feminist materialist scholarship supplies an ontology to critique humanist approaches, and establishes the foundation for a posthuman sociology of environment, in which (post)humans are an integral but not privileged element. We consider the implications of this perspective for both sustainability policy and ‘climate justice’. A posthuman ontology leads to the conclusion – perhaps surprisingly, given the anthropogenic roots of current climate change – that some unusual human capacities are now essential to assure environmental potential.