Anthropogenic sea-level rise (SLR) is predicted to impact, and, in many cases, displace, a large proportion of the population via inundation and heightened SLR-related hazards. With the global coastal population projected to surpass one billion people this century, SLR might be among the most costly and permanent future consequences of climate change. In this Review, we synthesize the rapidly expanding knowledge of human mobility and migration responses to SLR, providing a coherent roadmap for future SLR research and associated policy. While it is often assumed that direct inundation forces a migration, we discuss how mobility responses are instead driven by a diversity of socioeconomic and demographic factors, which, in some cases, do not result in a migration response. We link SLR hazards with potential mechanisms of migration and the associated governmental or institutional policies that operate as obstacles or facilitators for that migration. Specific examples from the USA, Bangladesh and atoll island nations are used to contextualize these concepts. However, further research is needed on the fundamental mechanisms underlying SLR migration, tipping points, thresholds and feedbacks, risk perception and migration to fully understand migration responses to SLR.

International audienc

It is plausible that the impacts of climate change will render certain nation-states uninhabitable before the close of the century. While this may be the fate of a small number of those nation-states most vulnerable to climate change, its implications for the evolution of statehood and international law in a “post-climate” regime is potentially seismic. I argue that to respond to the phenomenon of landless nationstates, international law could accommodate an entirely new category of international actors. I introduce the Nation Ex-Situ. Ex-situ nationhood is a status that allows for the continued existence of a sovereign state, afforded all of the rights and benefits of sovereignty amongst the family of states, in perpetuity. In practice this would require the creation of a government framework that could exercise authority over a diffuse people. I elaborate on earlier calls to use a political trusteeship system to provide the framework for an analogous structure. I seek to accomplish two quite different but intimately related tasks: first, to define and justify the recognition of deterritorialized nation-states, and, second, to explain the trusteeship arrangement that will undergird the ex-situ nation. In doing so, I introduce the notion of a post-climate era, in which the very structure of human systems—be they legal, economic, or socio-political—are irrevocably changed and ever-changing.