In this chapter, we review the physical processes that affect the elevation of coastal settlements relative to the sea, and identify current and projected rates of change, describe the impacts of MSLR on coastal settlements and on small island states, provide rough estimates of the number of people exposed, identify options for in situ adaptation, describe common challenges in implementing planned relocations of communities at risk, with case studies from the Carteret Islands and Fiji, and conclude by reviewing the cascading risks faced in Bangladesh.

This chapter provides an introduction to climate-related migration and displacement in the distant and more recent past, an overview of the basic natural science processes behind anthropogenic climate change for readers that require one, a review of how the impacts of climate change in a general sense present risks to individuals, households and communities, and how vulnerability and adaptation shape these risks, a summary of the social science on how migration decisions are made and the general types of patterns and outcomes that emerge, and a consolidated picture of how climate hazards interact with non-climatic processes to shape migration and displacement.

The present chapter focuses on migration and displacement associated with events that are directly linked to hotter air temperatures and/or an associated lack of moisture experienced at local and regional scales: droughts, increased aridity, desertification, heat, and wildfires. With the exception of wildfires – which share many characteristics comparable to rapid-onset extreme weather events – the hazards assessed in the present chapter are gradual in their onset and impacts. Their impacts accumulate with each passing week, month, and/or year, steadily eroding the water, food and/or livelihood security of households and communities. The slow rate of onset allows exposed populations an opportunity to adjust and adapt through means that do not require changes to existing mobility practices and patterns, sometimes referred to as in situ adaptation responses. It is only after hot and/or dry conditions persist beyond a particular threshold of duration and/or severity that in situ adaptations no longer prove to be sufficient and changes in migration decision-making and outcomes emerge.

In this chapter, we review approaches to model climate-related migration including the multiple goals of modeling efforts and why modeling climate-related migration is of interest to researchers, commonly used sources of climate and migration data and data-related challenges, and various modeling methods used. The chapter is not meant to be an exhaustive inventory of approaches to modeling climate-related migration, but rather is intended to present the reader with an overview of the most common approaches and possible pitfalls associated with those approaches. We end the chapter with a discussion of some of the future directions and opportunities for data and modeling of climate-related migration.

This chapter reviews how climate change is projected to affect the frequency, severity and/or spatial distribution of tropical cyclones, severe storms that generate tornadoes, and floods; the factors that influence people’s exposure and vulnerability to such events; adaptation options for reducing displacement risks; and, common characteristics of migration and displacement across all categories of extreme weather events. We then focus on specific types of extreme weather and provide more detailed analyses and case studies of migration and displacement events associated with tropical cyclones, tornadoes, and floods.

Scholarly understanding of these topics has evolved rapidly over recent decades, yet there is still much we don’t know about the complex ways that climate change interacts with migration decisions. In this final chapter, we discuss a number of emerging issues and future research needs including: gendered dimensions of migration in the context of future climate change, how climate-related migration affects Indigenous populations and cultural heritage, the interplay between climate-related migration and human health, the impacts of climate-related migration on receiving communities, identification of critical thresholds in climate-migration connections, and unforeseeable climate-migration outcomes.

This chapter provides an overview of policymaking that is being done at international, regional, and national levels, highlighting some of the key processes and frameworks relevant to climate-related migration and displacement. We discuss the extent to which these policies respond adequately (or not) to the needs and complexity of the challenge. We also describe a range of actors that have been actively engaged in these policymaking processes and the nature of their influence on these processes. We assess the different levels of actors in descending order of scale, starting with an overview of international policy frameworks and processes and then moving through regional and national level processes and approaches. Although we assess each level separately, they should be viewed as a network or web of interconnected actors and processes that influence one another, even as they evolve.

Introduction

Climate influences human migration. Sometimes the influence is direct and obvious, such as when people flee their ruined homes in the wake of a hurricane or tornado and do not return. Sometimes its influence is more subtle, such as when a string of dry years prompts an aging farmer to decide it is time to sell the land to a younger family and move to town. Sometimes climate’s influence is nested so deeply in interwoven chains of past events that we no longer notice how it has shaped where, how, and why we live in the places we do. It is not some random act of chance nor deliberate human plans that led southern England, southeastern Australia, and northern New Zealand to become the most densely populated regions of their respective countries, home to urban centers that continue to draw migrants from around the world. Climate played a role.

It is estimated that there are approximately 215 million international migrants worldwide (UN DESA 2011). Relatively few of them migrated for reasons directly and obviously tied to climate. If asked why they moved, most would likely answer that it was because of family reasons, or to search for work or new opportunities. Some might say they had to, because their household had grown too big to be able to support them. An unfortunate number, perhaps 20 per cent of the total, would answer that they had no choice, that they were forced to move because of violence, persecution, or natural disasters (some of which might be climatic in origin). Because climate is in proportional terms so rare a proximate cause of migration, scholars who specialize in migration research have largely tended to consider it in passing, if they consider it at all. Check any textbook used to teach undergraduate courses in migration over the past few decades, and you will find few mentions of climate.

Introduction

Of the various types of natural hazards to which human settlements are exposed, flooding affects the greatest number of people worldwide (Jonkman 2005). The Millennium Ecosystem Assessment suggests as many as 2 billion people worldwide may live in areas exposed to flooding risk (Millennium Ecosystem Assessment 2005). The vast majority of the world’s nations – an estimated 85 per cent – have experienced significant flood events in recent decades (Bakker 2009). Like droughts and extreme storms, floods are inherent, regularly occurring outcomes of climatic processes. In some regions, flooding is an annual risk because of high seasonal variability in precipitation. In others, floods occur irregularly. The size and scale of the human impacts of extreme floods can be tremendous. There are the immediate risks of death from drowning or injury from flowing debris, outbreaks of waterborne and insect-borne diseases generated by standing waters, and the longer-term mental health effects of experiencing such a crisis (Ohl 2000, Ahern et al. 2005). Housing, businesses, and critical infrastructure may be destroyed or damaged, creating enormous financial costs and requiring much time and effort to repair and replace. Yet, while floodplains are inherently hazardous, they also tend to make especially suitable locations for human settlements, providing easy access to fertile soils, potable water, hydraulic flow for irrigation and powering turbines, and the potential to transport goods and people by boat. Researchers estimate floodplains provide more than a quarter of all ecosystem services consumed by humans, despite representing a small fraction of the Earth’s surface (Tockner and Stanford 2002). It is therefore not surprising that human population numbers continue to rise in many of the world’s most flood-prone river valleys and deltas despite the risks.

Introduction

Scholars in many disciplines pursue migration research from a variety of perspectives, each discipline bringing with it a range of favorite theoretical and methodological tools (Brettell and Hollifeld 2007). No grand unifying theory exists that explains human migration behavior in all its aspects, and there are no signs that one is soon to be developed. There is, however, great complementarity in the various ways scholars have sought to explain migration, each such method making its own useful contribution to a broader understanding. In exploring migration in the context of human adaptation to climate, it is useful to first review important explanatory concepts from across disciplines and describe how these can help clarify human migration behavior more generally.

The migration process can occur across a range of spatial and temporal scales, and involve many potential actors, institutions, and systems. From the perspective of an individual migrant, the process spans the period from when he or she first contemplates the possibility of moving, through the decision-making process, the act of moving, and on into the period of adjustment at the destination. For some migrants, the process may eventually include a return to the place of origin, or lead to becoming a member of a translocal or transnational community that maintains connections and perpetuates migration between the sending and the receiving area. For migrants who travel short distances and remain within their same cultural community, the migration process may be relatively uncomplicated. For migrants travelling long distances to settle in new and unfamiliar places, migration may be a long and arduous process, with integration into the destination population never completed within the migrant’s own lifetime, but continued by subsequent generations.