This chapter outlines the remaining constitutive elements of the ecological security discourse, noting what means it encourages in responding to the threat climate change poses to ecosystem resilience and developing an account of which actors have responsibility for the preservation or advancement of security in this discourse. On the question of means, the chapter argues that an ecological security discourse encourages a focus on significant mitigation action, while also noting a potential role for adaptation to inevitable effects and even controversial practices associated with geoengineering. It notes in the process what sets of principles should inform how we approach such practices, emphasizing the importance of dialogue, reflexivity and humility in ensuring that practices carried out in the name of ecological security serve to minimize harm to the most vulnerable. The chapter then defines responsibility for addressing ecological security in terms of capacity, noting a potential role for a wide range of actors – from states to intergovernmental organizations, private corporations to individuals – in advancing ecological security in practice.