This thesis seeks to analyze the ways through which issues related to the environment, especially climate change, interact with local conceptualizations of security in communities which are severely threatened by these problems and, at the same time, profoundly excluded from security studies debates. Within International Security Studies (ISS), the climate crisis persists in being analyzed through state-centered, militarized and us x others dynamics. When this is not the case, environmental challenges are placed within a human security logics, animated by a modern and liberal understanding of what is supposed to be secure and thus, disregarding the role of local understandings and needs. (Shani, 2017) By focusing on non-scientific security narratives, I expect to unveil the contingencies of the hegemonic discourses within ISS that, rather than being rational and based on an authentic description of reality, contribute to aggravating the security challenges faced by some individuals, such as the Marshallese. Animated by rational security discourses promoted by realist and strategist thinkers, during the Cold War, the Marshall Islands was turned into a testing ground for 67 thermonuclear weapons. The bombs - considered by security theorists and policy-makers both as a source of power and as a legitimate way to obtain security – vaporized islands, forced the permanent evacuation of entire communities, disrupted the Marshallese land-based matrilineal organization and their ancestral ties to their atolls. Nowadays, the Marshallese archipelago and its inhabitants are once again being challenged: not by the military security goals of superpowers, but by an unintended and depersonalized threat. Climate change is the latest form of intervention, being preceded by a long list of other colonial and violent practices. As a low-lying atoll nation, it is very likely that the Marshall Islands will become inhospitable until the middle of the century as a result of the deteriorating climate effects. For the islanders, it will represent an immeasurable loss of territorial, spiritual and cultural references. In relying on cases such as the Marshallese, I aim to explore what new meanings and rationalities of security can emerge, or become more prominent, in the face of the challenges brought on by climate change. With this aim, the ontological security theory is presented as an insightful framework for the analysis of these cases where, what seams at risk is not only a physical survival of states, individuals and ecosystems, but also the preservation of a stable social and material environment of action and a sense of biographical continuity. (Giddens, 1990) With this critical move, I seek to emphasize other ways of thinking and experiencing (in)security; thus, enlightening how the meaning of this concept is undissociated from the political, cultural and emotional contexts from which security discourses emerge.