“Four thousand migrants arrive in Dhaka, the capital of Bangladesh due to various ‘push’ factors including frequent natural disasters” ¹ . Indeed, environmental changes due to climate change are projected to cause substantial increases in population movement, within and between countries, in the coming decades. Haiti faces a similar situation according to a 2008 report estimating that 100,000 people had moved for climate change reasons from rural areas to the capital Port-au-Prince ² . Environmental changes (e.g. drought, soil erosion, extreme weather events, etc.) lead to substantial impact on health, economic and political dimensions at the population level, including influencing migration patterns and may result in adverse health outcomes, both for displaced and for host populations, as we will discuss in more detail later ^{3– 5} . Consistently, the World Health Organization (WHO) identifies climate change as a defining challenge of the 21 ^st century; and considers it an emerging priority for the public health community to ensure protection against its health impact ^{6, 7} . In 2015, The Rockefeller Foundation and The Lancet published the report of the Commission on Planetary Health ⁸ and the UN Sustainable Development Goal 13 calls for “urgent action to combat climate change and its impacts".

For this article, we conducted an heuristic literature review on climate change, migration and health systems. As a result of a peer-reviewed article search in the PUBMED database using climate change, health systems, and migrants as keywords, only 10 results published between 1994 and 2017 were identified. Of these, six (60%) were written in the past decade and included: two opinion papers, two study reviews, one qualitative study, and one protocol for a review that will be completed in 2018.

In this article, we describe and discuss the fundamental role that health care systems resilience can play in this regard and we identify interdisciplinary research as key to better understand the existing linkages between climate change, migration and health systems and how to build more resilient health systems. We also propose some questions and axes to orient future research proposals.

Climate change can be translated into a wide range of environmental degradations, including hurricanes ⁹ , rising sea levels, and/or reduced rainfall in drylands and water scarcity ¹⁰ . Populations confronted by climate change consequences such as exposure to hazards, loss in land productivity, absence of habitability, and/or shortage of food/energy/water security may have difficulties to subsist in a given area ¹¹ . Climate change consequences compounded by socio-economic pressures and/or political instability, increase propensity to migrate. Although evidence is still missing to prove this association, environmental factors are increasingly influencing an already complex pattern of human mobility. A recent paper suggests “ a statistically significant relationship between fluctuations in asylum applications and weather anomalies” ¹² . Climate migrants may be forced to leave their homes due to rapid-onset disasters, such as flooding and hurricanes (as in Haiti and Bangladesh for example) ^{1, 2, 13, 14} .

Nowadays, there is no conceptual consensus on the notions of environmental refugee or climate change migrants yet, or the more rarely used terms ecomigrants or environmentally displaced persons ^{15, 16} . Since 2007, the International Organization for Migration (IOM) has defined environmental migrants as “ persons or groups of persons who, for compelling reasons of sudden or progressive change in the environment that adversely affects their lives or living conditions, are obliged to leave their habitual homes, or choose to do so, either temporarily or permanently, and who move either within their country or abroad” ¹⁷ . Others suggest restricting the definition to victims of extreme weather, drought/water scarcity, and sea-level rise and excluding the effects of the spread of tropical diseases ¹⁶ . The estimation that is most widely accepted is that over 200 million persons will be displaced globally by 2050 because of climate change ^{13, 15, 18} , and according to the last Lancet Countdown “ the total number of people vulnerable to migration might increase to 1 billion by the end of the century without significant further action on climate change” ⁵ .

Climate-related migrants may or may not perceive how climate change influences and has an impact on their health needs and social patterns. For example, in Burkina Faso, the close relationship between climate change and flooding is not always fully perceived by the Burkina population suffering from it, as documented by the authors of this manuscript in previous studies ( Box 1) However, climate-related migrants experience difficulties or face challenges similar to those of refugees fleeing war and/or political persecution: overcrowded settlements, unsanitary conditions, poor nutritional status, unsafety, inequity and limited access to health services ^{1, 2, 19, 20} . In addition, environmental change migrant population is usually the most vulnerable as well because migration is often expensive and climate change factors can easily lie on the top of other strong socio-economic factors. For example, Haiti and Bangladesh were respectively ranked 3 ^rd and 6 ^th globally in the Long-Term Climate Risk Index (CRI) from 1995 to 2014 ²¹ , while their health systems’ performances were ranked by the WHO in 2000 as 138 ^th and 88 ^th, respectively, out of 191 countries ²² . The very recent Global Climate Risk Index 2018 confirms these two places for Haiti and Bangladesh but also shows that several African countries (Mozambique, Malawi, Ghana, Madagascar) are very affected and have little research on climate migrants. ²³ .

In parallel, some individuals might be escaping slow-onset disasters, such as rising sea levels and declining agricultural yields; their migration patterns may be more similar to those of rural–urban migrants, and they might experience many similar obstacles and barriers to their health as well ²⁸ . From the literature, it can be seen that some health related challenges may be identical: 1) Re-emergence of infectious diseases and geographical migration of diseases ²⁹ : migrants spatially re-distribute infections from endemic areas to new populations; they are also exposed to new diseases due to unsanitary living conditions. 2) Reduced access to healthcare services: mass migration applies population pressure exceeding local health and social services capacity; perceptions of long wait times, confusing administrative procedures, or discrimination also impede health system access for migrants ³⁰ . 3) Disrupted social support networks contribute to adverse mental health outcomes ³¹ , higher risk of violence, and spread of STIs, including HIV infection. Migrants are often seen as potential security challenges for countries ^{18, 32} . Niger is one example for conducting more research to understand the phenomenon of infection diseases and migration, but at the same time for the health system to better adapt ( Box 2)

However, the lack of consensus of climate change migrant definition makes research on its health needs and patterns still difficult.

With its inclusion in Goal 3 of The Sustainable Development Agenda, the concept of Universal Health Coverage (UHC) has obtained consensus from the international community ³⁶ . UHC, regarded as the third global health transition ³⁷ , or, according to former WHO director Margaret Chan, “ the most effective concept that public health can offer”, aims at ensuring access to good quality care while limiting the impoverishment of people as a result of their illness ³⁸ . In September 2015, the Director of WHO/PAHO for the Americas, Carissa F. Etienne, stated that “ we must all cooperate to reduce those factors that are contributing to climate change and to mitigate its health effects.” Consecutively, in September 2017, the new WHO Director-General has set UHC as his greatest challenge and highlighted at the UN General Assembly on Migration Health in New York City that “ health systems must be sensitive to the needs of migrants.” The direct and indirect effects of climate change on population health and disease development are now well discussed ^{5, 39} , but there is still little literature on the health effects of migration (within and between countries) influenced by natural disasters and droughts exacerbated by climate change ⁵ . In addition, the role of the health care system as a social determinant of health ⁴⁰ and its capacity to protect populations affected by climate change was recently identified by the WHO ⁶ and the Canadian Public Health Association ⁴¹ .

Health systems (and health professionals) suffer the shocks provoked from climate change and migration ^{42, 43} . These shocks can be the direct consequence of climate change (floods, heat waves, hurricanes, etc) or indirect effects, i.e. the influx of patients suffering from diseases whose emergence or abnormally high frequency is due to climate change ⁴⁴ . Therefore, health care systems need to adapt to population migrations (in and across countries) due to climate changes by taking into account the effects of both phenomena on the epidemiology of diseases ⁴⁵ (e.g. dengue vs malaria) and, more globally, by identifying and responding to specific social (e.g. social acceptability of migrants) ⁴⁶ and health problems (e.g. mental health) in this context. In this sense, there is a very close link between UHC and emergency preparedness, as the WHO has just pointed out calling for “ a mutual reinforcement of emergency preparedness and health systems strengthening strategies”. Health security must also be achieved through good health systems preparedness for the disasters caused by climate change ⁴⁷ . The capacity of health systems and their actors to prepare for and adapt to these climate-related shocks is known as resilience.

Resilience is a longstanding concept in the disciplines of life sciences, psychology ( Box 3) and climate change ⁴⁸ , but it is relative new to the study of health systems ^{43, 49, 50} . Health system are compounded of both hardware (structure; organization; technology; resourcing) and software (values; norms; actors; relationships) components, and their resilience require to be measured and understand accordingly ⁵¹ .

In 2015, the WHO proposed an operational framework to build climate resilient health systems within the context of climate change ⁴² , but the scientific and empirical basis for its production is unclear, and the issue of population migration is not mentioned

Recently, an article has developed a non-normative index for assessing the resilience of health systems, but its validation has not yet been completed ⁵⁶ .

The 2017 and 2018 Lancet Countdown paper series suggests some indicators (at least: 2.1, 2.4, 2.6; 2.7, 2.8, 3.9) ( Box 4), which could be useful to understand the link between climate change and health system resilience, even though the concept of health system resilience adoption is still limited and “ does not capture the quality or effectiveness of efforts”, as it was said for the 2017 report ^{5, 57} neither the resilience of health staff (at its already important brain drain) nor community is taken into account. Health systems’ resilience cannot be evaluated only in terms of infrastructures. In contrast, from a more holistic and fundamental research perspective, several recent articles propose conceptual frameworks ^{49, 50, 56} that suggest analysing the five main dimensions of a resilient system: awareness, diversity, self-regulation, integration, and adaptiveness ⁵⁰ .

In addition, according to the Sendai Framework (2015-2030) adopted at the Third United Nations World Conference on Disaster Risk Reduction in March 2015, it is essential “ to enhance the resilience of national health systems” ⁵⁸ but very little attention has been paid to the role of the health system in responding to climate change and its resilience ^{42, 43, 59} . One of the major global health journals ( Health Policy and Planning) just released in November 2017 the first, to our knowledge, supplement issue about “Resilient and Responsive Health Systems” ⁶⁰ . But none of the 11 articles addressed climate change.

As seen and cited, migration and climate connections has followed similar research progress, typically by a different group of scholars, on understanding migration’s health dimensions ⁴⁵ . In the same way, migration, climate, population’s health and resilience of health systems are usually analysed as separated components through disciplines and approaches in silos. Research on the intersection between all these components is still very scarce. Consequently, there are gaps and a predominant compartmented analysis on the existing links between all of them. In contrast, interdisciplinary means a certain level of integration of knowledge, methods and/or ideas to construct and analyse the problematic under study ^{61, 62} . Hence, interdisciplinary research can lead to the understanding of the links between migration and health require mixed methods ⁶³ , and the collaboration of environmental, health and social sciences, in order to inform strategies and interventions to protect population health. “ By learning from other researchers one increases the possibilities of creative solutions” ⁶⁴ .

Climate change is one of the main challenges of our century, having the potential to trigger important changes in population health also by forcing migration. The role of health systems in the context of targeting universal health coverage may be central to address these challenges.

As exposed in this manuscript, the research on the intersection between climate change, health systems, and migrants is still very scarce. Because of its complexity, we need to move from a multidisciplinary to an interdisciplinary approach ⁶⁴ to understand the multiple pathways that link migration driven by climate change and population’s health.

We believe there is a need for an interdisciplinary approach relying on the concept of resilience to help to study adaptive strategies in both places of origin and destination. Further investments should be made to unravel the link between climate change, migration, and health system resilience. We propose a series of interdisciplinary research questions to provide initial guidance in this direction ( Box 5). We suggest in Table 1 and Figure 1 a first summarization attempt of the challenges triggered by climate change for the resilience of health systems.

No data are associated with this article.