Public health and policy responses to address health risks associated with climate-related migration must be responsive to the nature of mobility and the demographic characteristics of those who move. Broadly, it is important to a) minimize any health inequities and ensure access to services, b) ensure health rights of migrants, c) implement interventions to reduce excess mortality and morbidity among migrant populations, and d) minimize the negative impact of the migration process on migrants’ health outcomes (). Meanwhile, much can be learned from the existing evidence base and policy and programmatic responses in the area of large-scale population displacement (e.g., after humanitarian crisis and disaster), planned resettlement schemes, and urbanization (specifically settlement in urban poor areas in developing countries).
There is an extensive and well-established international regime for responding to large-scale humanitarian and environmental disasters, such as conflict, droughts, and floods. A fundamental role of public health and disaster relief services—provided by government authorities, international humanitarian agencies, UN organizations, and local and international non-government organizations—is to assess health needs, allocate resources, and provide health services. Of fundamental importance are the accessibility and quality of health care, health education, and prevention measures; establishment of adequate disease surveillance systems; control of pathogenic agents; targeting “hidden” populations; monitoring and evaluating health interventions such as vaccination coverage; participation of affected populations in health care planning; coordination between services and administrative bodies and target populations; and consideration of the health needs of host populations ().
Research on climate change and movement of people has been dominated by studies seeking to estimate likely population numbers, and the pathways by which movements might occur (e.g., ; ; ; ; ). Estimates are based on broad-scale assessments of exposure to risk, rather than systematic evidence about the sensitivity of human movements to particular environmental changes. They have not considered projected demographic and socioeconomic changes over coming decades or the extent to which adaptation may offset climate impacts and hence the need for migration [; ; ]. The arguments have been largely normative, and the scale of analysis large and hence low in resolution. A frequent assumption is that climate-related population movement, like migration more generally, poses a threat to the integrity of states and their borders (see )—and a risk to political stability and hence a source of increased violent conflict [; ; ; ; ; ].
Meanwhile, there has been little research on the impacts of climate-change–related migration on “everyday lives,” including health, humanitarian, and equity aspects (; ). Yet, the health risks posed by climate-related population movements are likely to become a major source of human suffering, disability, and loss of life—an outcome that, currently, appears more likely than the much-debated possibility of increased violent conflict or state failure (). Consideration of these human-scale outcomes of climate-related movements remains greatly overshadowed by grander geopolitical narratives ().
Today, for the first time, human-induced global climate change is beginning to press on populations . There is now an overwhelming majority consensus among climate scientists that human-generated emissions of greenhouse gases are initiating climatic changes that are unprecedented in human experience during the Holocene epoch. Human amplification of the natural “greenhouse effect” reflects the scale and intensity of energy use and economic activity that have arisen during the industrial era, along with the accompanying surge in human numbers and consumption levels (particularly in high-income countries), land use patterns, and food production activities over the past century (; ; ). An increasing body of evidence shows that climate change is already affecting natural systems. Of the > 28,000 cases of significant observed changes in terrestrial and biological systems, > 90% had directions of change consistent with impacts expected from global warming (). On current trajectories, within the next 50 years climate change is likely to reach a critical stage that will be dangerous to the functioning of many aspects of the natural and social environments upon which human societies depend for well-being, health, and survival (; ; ).
In this review, we focus on the health dimensions of future climate-related population movements. After a brief discussion of the likely relationship between climate change and population movement, we examine two key themes relating to health, climate change, and population movement: the risks that climate change poses to human health, and how this may contribute to population movement; and the specific health implications of potential climate-related population movements, particularly the health risks to forcibly displaced people, to those involved in resettlement schemes, and to those who migrate to urban areas. Given the nascent status of this research topic, we necessarily draw on previous studies of refugees, people in resettlement schemes, and migrants as analogs for the health issues associated with future climate-related movements. Finally, we discuss the types of research and policy responses needed to address health issues associated with climate-change–related migration.
Adaptive strategies to lessen risks, plus public health preparedness, can help build community resilience and reduce vulnerability to climate change. The National Adaptation Programmes of Action (NAPAs) provide an avenue for least developed countries to respond to their climate change adaptation needs (). An analysis of 41 of 49 NAPAs submitted to the United Nations Framework Convention on Climate Change as of May 2009 indicates that many NAPAs explicitly recognize the linkages between climate change and human health, and 18 link climate change to migration (). However, review of the NAPAs found only two examples in which mobility was identified as an adaptation strategy.
Finally, although popular discourse suggests that migration reflects a failure to adapt to climate change, migration is also an adaptive response that will allow migrants, their families, and the communities they move between to cope with the effects of climate change (; ; ). Rural–urban migration is often circular, and migrants continue to maintain links with rural areas and participate in development of regions of origin. Migration can benefit those left behind in environmentally degraded areas, reducing poverty through remittances that can be spent on food, clean water, and health care. Research in Côte d’Ivoire has shown that migrants from Burkina Faso send home remittances that are invested in schools, hospitals, and water and irrigation systems (). Migration can also provide a coping strategy that diversifies and strengthens people’s livelihoods, assets, and incomes, which in turn helps to reduce food insecurity and improves access to health care (; ). Although significant challenges are associated with migration, including health risks, migration is also a strategy that can potentially reduce vulnerability.
There is evidence that rural–urban and international migrants are at higher risk of developing chronic diseases, such as cancer, hypertension, coronary heart disease, cardiovascular disease, and type 2 diabetes, compared with those in places of origin (; ). For example, among Mexican-born immigrants, length of U.S. residency is directly associated with increasing risk of obesity (). The increased incidence of chronic disease after rural–urban and international migration, relative to source populations, has been attributed to changes in diet, acculturative stress, physical inactivity, isolation, and increased health risk behaviors such as smoking and hazardous use of alcohol (; ; ; ; ). Poor chronic disease outcomes are also due to lack of access to health care services, including preventative health care and early diagnosis ().
These challenges will remain central to public health responses in the case of climate-change–related population displacement, particularly during sudden-onset disasters. Pre-disaster planning can increase the impact of international assistance and aid and decrease the public health tolls (). To respond to potential increase in large-scale disasters, it will be necessary to build on existing frameworks that seek to prepare for, respond to, and recover from public health issues in situations of large-scale population displacement (e.g., ; ).
Migration provides an adaptive strategy in response to perceived or actual threats associated with climate change (; ). However, the urban poor, particularly those in crowded settlements with poor water and sanitation facilities, are prone to ill health (; ). Accelerated population growth, notably the expansion of slums or neighborhoods in vulnerable areas, places stress on urban socioeconomic conditions and facilities (e.g., labor markets, education and health care services, public safety). Poor urban settlements are typically neglected by local or national government authorities and have inadequate infrastructure, high rates of underemployment, and income instability ().