Mobility and Health in the Context of Climate Change: A Systematic Literature Review and Meta-Synthesis of Policy Recommendations

Changing mobility patterns combined with changes in the climate present challenges and opportunities for global health, requiring effective, relevant and humane policy responses. This systematic literature review sought to synthesize the existing policy recommendations related to the literature examining the intersection of climate change, migration and health to strengthen the evidence-base. Systematic searches were conducted in four academic databases (PubMed, Ovid Medline, Global Health and Scopus) and Google Scholar for empirical studies published between 1990 – 2020 that used any study design to investigate migration and health in the context of climate change. Studies underwent a two-stage protocol-based screening process and eligible studies were appraised for quality using a standardized mixed-methods tool. From the initial 2,425 hits, 68 articles were appraised for quality and included in the synthesis. Among the policy recommendations, six themes were discernible: (1) avoid the universal promotion of migration as an adaptive response to climate risk; (2) preserve cultural and social ties of mobile populations; (3) enable the participation of migrants in decision-making in sites of relocation and resettlement; (4) strengthen health systems and reduce barriers for migrants to access health care; (5) support and promote optimization of social determinants of migrant health; (6) integrate health into loss and damage assessments related to climate change. The results call for transformative policies that support the health and wellbeing of people engaging in, or affected by mobility responses, including those whose migration decisions and experiences are influenced by climate change, and to establish and develop inclusive migrant healthcare.


INTRODUCTION
Extensive research has considered the consequences of climate change separately for: (i) human migration, and (ii) human health. Firstly, climate change and migration research dates back over three decades; it indicates that while climate impacts shape the scale and nature of human migration, climate change does not act in isolation to drive mobility (Future Earth, 2019). Local environmental conditions interact with socio-economic, political, demographic and cultural circumstances to influence migration decision-making and patterns of mobility (Myers, 1993;Tickell, 1990 Secondly, the literature on climate change and health is also extensive and increasingly sophisticated yet lacks coverage of contexts where capacity to address population health is low and exposure to climate risks is high (Sauerborn, 2017;Herlihly et al, 2016). The climate change and human health literature is also underdeveloped in terms of investigating policy and governance processes, as well as the role of different stakeholders in policy development (Bowen & Ebi, 2015).
It is helpful to consider the broad international policy context relevant to the areas of climate-migration and climate-health. A plethora of international agreements incorporate climate change and migration, and climate change and health. For example, central to the Sustainable Development Goals (SDGs) is the principle of leaving no one behind and universal health coverage can only be attained by ensuring migrant access to health systems (Vearey et al, 2019). In addition to the SDGs, various agreements have been developed to address climate-related displacement. These include at the United Nations Framework Compact for Migration (UNHCR, 2018a) and the Global Compact on Refugees (UNHCR, 2018b) refer to people who move in the context of climate change and urge strengthened collaboration and solidarity with migrants and affected host countries. In terms of the policy context relevant to climate change and health, the Paris Agreement presents a firmer stance on the importance of health compared with The Kyoto Protocol, referring to "the right to health" in the preamble. Shifting from this international scale, there are also regional policy contexts that address climate change and human health; for example the Pacific Islands Action Plan on Climate Change and Health (WHO, 2018a) and the WHO's Special Initiative on Climate Change and Health in Small Island Developing States (WHO, 2018b).
As the climate crisis accelerates, it is timely to examine how migration might be more effectively and humanely governed (UNHCR, 2018a). There is concern that people moving in the context of climate and environmental change may slip through the cracks of existing migration protection frameworks, creating risks to their health. Yet it is important to understand and address the health of climate-related migrants as well as the health of people who migrate into, or remain in sites with climate-related health risks: appropriate policy frameworks and responses are required. This paper presents policy recommendations emerging from 68 publications reporting the findings of research focused on the climatemigration-health nexus. These publications are reviewed and synthesized to identify broader, principle-based recommendations at the nexus of climate, migration and health.
The aim of this review is to identify, analyse, evaluate and synthesise the policy recommendations in the literature investigating the nexus between climate change, health and migration. The specific objectives are to: a) synthesize policy recommendations from empirical evidence about the climate change-migration-health nexus and present key themes; b) analyse key methods employed and appraise the quality of the evidence; c) summarize study settings, populations, climate hazards, mobility responses, and health outcomes; and (d) identify overarching knowledge themes and gaps in the evidence base.

Protocol and Registration
The protocol for this systematic literature review was registered with the international platform PROSPERO on 29th August 2018 (Registration no: CRD42018095461). It was developed in consultation with the International Office for Migration (IOM), Migration Environmental and Climate Change Division. For reporting, we applied the RepOrting Standards for Systematic Evidence Syntheses (RoSES) Pro-forma and flow diagram. This framework integrates diverse methodologies and has been developed for environmental management and conservation research (Haddaway et al, 2017). In contrast, the PRISMA guideline (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) (Moher et al, 2009) has been created for systematic reviews and meta-analysis of clinical trials. Therefore, PRISMA was not applicable to the present study. The original search was conducted in December 2019 and was updated in August 2020 to capture current evidence.

Definitions
For the purposes of this systematic literature review, 'climate change' was defined as a change in the state of the climate that can be identified by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer (IPCC, 2018). 'Health' was defined according to the World Health Organization (WHO) as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (WHO, 1948

Nexus
Includes climate change, migration and health.
Focus on two elements (dyad) of the nexus (i.e climate-health, climate-migration). Focus Table 2 outlines the eligibility criteria, which were strictly applied to each study. The assessment included research investigating populations worldwide engaging in, or affected by mobility responses. These responses were on a spectrum from displacement, encompassing forced movements, to migration, which is considered predominantly voluntary, and also immobility. Populations from sending communities as well as mobile and host populations were included. The review required a climate hazard as at least one driver of human migration/mobility. If migration drivers were economic, political, social, and/or demographic and there was no explicit or implied link to climate change or climate variability, the article was excluded. If the hazard was not related to climate change (e.g. volcano, earthquake) the article was excluded. The review required studies to focus on health including at least one measurable health outcomes (e.g. prevalence of disease) or immediate determinant of health (i.e. food and water security). Studies that referred to social determinants of health as outcomes of human migration (e.g. income, employment) were excluded. Studies were not excluded based on design or quality. We considered all empirical research, using either primary or secondary data. Due to methodological ambiguity in the search results, the 'empirical' criterion was further refined to require a methodological explanation and a description of the data used. Modelling and qualitative case studies were included but commentary, editorials, and literature reviews were not.

Literature selection
In the first stage of screening, two authors decided whether the article was eligible by title and abstract review. Two votes were required to continue with the second stage of full-text screening. Inconsistencies between paired authors at both stages were resolved by an independent third author. No authors could individually decide about including their own work, because each study was reviewed by at least two independent reviewers. The screening process was blinded using the Covidence platform so that 'votes' to include or exclude could not be seen by the partner reviewer. Reference lists of included and excluded studies were scanned for relevant studies, which were then added to the Covidence platform for full-text review to reduce the likelihood that eligible studies were missed.

Data extraction
We used the Mixed Method Appraisal Tool (MMAT) to concomitantly describe and appraise the selected studies. The MMAT tool has been specifically developed for systematic mixed studies reviews that include both qualitative, quantitative, and mixed methods studies (Hong et al, 2018). Therefore, this tool was considered better suited than Cochrane tools for clinical studies. Extraction codes were predetermined by reviewers and aligned with the aims and objectives. In this review, recommendations for policy, practice or further research were the focus but climate hazard, mobility response, health outcomes, study design, population and study setting were extracted. Due to the heterogeneity of the results, a metaanalysis was not feasible (even of the quantitative studies because the health outcomes and measurements were diverse) and a meta-synthesis was conducted using thematic analysis methodology (Braun & Clarke, 2006). The data were extracted in separate word documents and uploaded to N-VIVO (version 12) and analyzed. Two authors (PNS, JS) reviewed all 68 selected studies in full-text and simultaneously conducted the quality appraisal and data extraction. When consensus could not be reached regarding extraction coding or quality appraisal, a third independent author (CM) was consulted. When data were incomplete, unclear, or missing, an attempt was made to contact the authors of eligible studies.

Quality assessment
The quality appraisal tool MMAT version 2018 was chosen a priori and used to identify threats to internal and external validity for all eligible studies. MMAT provides five custom questions for each study design (qualitative, quantitative randomized controlled trials, quantitative non-randomized, quantitative descriptive, and mixed methods), pertaining to both study and reporting quality (Hong et al, 2018). Quality appraisal results were recorded in the results spreadsheet along with other coded findings in the overview table (Table 3).
Five modelling studies could not be appraised by the MMAT and this remains a limitation of this systematic assessment (marked no category in the overview Table 3).

Data analysis and synthesis of results
All eligible studies were included in the analysis. A meta-synthesis was undertaken which is considered advantageous when dealing with broader research questions with disparate outcomes (Buchenrieder et al, 2017). Meta-synthesis is a synthesis of qualitative evidence.
We used a meta-aggregative approach to the synthesis that is sensitive to the practicality and usability of the original findings of selected articles and does not seek to re-interpret those findings, as some other methods of qualitative synthesis do (JBI 2020). Once policy recommendations were extracted from the selected papers they were analysed using N-VIVO and the six steps outlined by Braun and Clarke (2006), namely: familiarization with data; generating initial codes; searching for themes; reviewing themes; defining and naming themes; producing the report which included meaningful data presentation and visualization. The quality of the included studies was a component of the meta-synthesis.
All authors were involved in and approved the thematic analysis that resulted in six themes.

Included studies
The search strategy revealed 2,425 studies with 134 duplicates that were removed. We

Study settings
The 68 eligible studies were conducted in 36 countries. If one study included more than one country, it was duplicated in the analysis so that there were 81 study sites altogether ( Figure   3). Most studies were conducted in the South East Asian region (36%) followed by the  Table 3.

Quality appraisal
Each study was individually appraised for quality using the MMAT tool (see Figure 4) (Hong et al 2018). For individual studies, the quality score was attained by using the five custom questions for each study. We used a ranking system to summarize overall quality, based on the study's adherence to each of the quality criteria questions. Namely, how often (%) we could answer 'yes' to the quality appraisal question for a particular method according to MMAT (***** 100%, ****80%, *** 60%, ** 40% * = <20%).
Overall, the quality of the included studies was high with the quantitative non-randomised studies (n: 12) achieving the highest quality assessment result, with 67% scoring between 'good' and 'excellent' and no studies being appraised as poor (See Figure 4).    Table 4 (Note: Additional illustrative quotes, codes and study details available as supplementary material) 1 of 48 'The policy implication is that governments should not make assumptions a priori about whether a location is undesirable and promote migration as a blanket solution to the negative impacts of climate change' (Adams, 2016, Quantitative descriptive, Peru).

Preserve cultural and social ties of mobile populations.
Strengthen governance of socio-ecological systems.
"Developing government frameworks that can draw on the strengths of the community-led approaches to relocation whilst also providing a mechanism for communities to stay intact will be an important step forwards for Small Island Developing States (SIDs) facing these climate pressures" (Albert et al, 2018, Qualitative case studies, Alaska and Solomon Islands).
3. Enable participation of migrants in their sites of relocation and resettlement. Support the self-sufficiency of both incoming and host communities by supporting new livelihoods, developing social networks, and integrating cultural considerations. 5. Provide migrants with the requirements and the determinants for good health.
"The rights of these displaced people, including the right to health, are often poorly protected in practice. More vigorous application of existing human instruments is needed, as well as clarification and possibly re-definition of the rights of those displaced" (Rahaman et al, 2018, Qualitative, Bangladesh).
6. Integrate health into loss and damage assessments. Including for people at higher risk, such as those that are immobile or trapped.
"The findings outlined a long line of climate-induced non-economic losses and damages that people faced through the rural-urban move from the island, and through the displacement in the slum. These included the loss of identity, honor, sense of belonging, physical and mental health or wellbeing" (Ayeb Karllson et al, 2020, Mixed methods, Bangladesh).

DISCUSSION
This review highlighted a paucity of research on the nexus between climate change, migration and health. The geographical settings where this nexus research has taken place to date, the predominant study designs, their quality, and the relationships between climate hazards, mobility responses and health outcomes are discussed below. Finally, a narrative synthesis of the policy recommendations extracted from the included studies is placed in the context of the current policy environment on this topic.

Study settings
The predominant geographical foci of the studies in this review; Sub-Saharan Africa, South Asia and Latin America. Bangladesh is of particular interest to climate change, migration and health studies possibly, because it is highly exposed and vulnerable to climate hazards, densely populated.
These regions identified in the research align with existing evidence that indicates that currently, most climate-related migration is internal and takes place in developing countries

Study designs and quality appraisal
The included quantitative descriptive studies (n=17) mainly consisted of surveys and case reports. Some of these studies looked at the association between climate hazards, migratory behaviours and health outcomes and sought to determine the extent to which migration was adaptive or maladaptive. Overall, the quality of quantitative descriptive studies was high with 71% of studies scoring between 'good' and 'excellent' (See Figure 4). Analysis ranged from simple descriptive statistics to regression analyses.
The included quantitative non-randomized studies (n: 12) mainly consisted of crosssectional analytic studies that were used to study climate exposures without using randomization to allocate units to comparison groups. These studies tended to compare migrating and non-migrating households and resultant health outcomes, or climatevulnerable and less climate-vulnerable households. Overall, the quality of quantitative nonrandomized studies was high with 67% of studies scoring between 'good' and 'excellent'.
This was the only category of studies without any scoring 'poor' quality. Quality issues included mismatching of temporal-spatial scales of the hazard, mobility response, and health outcomes and inadequate demographic matching of comparison groups.
Included qualitative studies (n=17) mainly consisted of case studies and narrative research.
Qualitative methods were used to explore and explain in-depth the issues intrinsic to a particular case of climate-related migration and health. Overall, the quality was high with 65% of studies scoring between 'good' and 'excellent'. Qualitative studies with higher MMAT scores described data collection in detail and derived findings clearly from the data (e.g. using quotes to substantiate themes). Improvements could be made by clearly demonstrating coherence between data sources, collection, analysis, and interpretation.
The included mixed methods studies (n=17) combined quantitative descriptive studies (mostly using surveys) with qualitative methods (mostly using focus groups or interviews).
Mixed methods seem to be well suited to the topic due as methods can complement each other and provide further details and explanations. The quality was high overall with 65% attaining a 'good' or 'very good' rating with no studies achieving excellence according to MMAT criteria. Stronger studies balanced the emphasis on different methods, adhered to the quality standards for both qualitative and quantitative components, and integrated findings arising from different methods.

Relationships between climate hazards, mobility responses, health outcomes
The relationships between mobility and health are complex and the extent to which they are    The studies we review here all discuss the policy and practice significance of their findings.
Most note that the scale of climate-related migration is projected to increase in the coming decades (while also noting that climatic factors rarely act alone in shaping human mobility) and that there are health risks and opportunities of climate-related mobility. Climate change is likely to act as an amplifier of health risks among mobile populations, rather than creating new vulnerabilities that require distinct policy and practice responses. Nevertheless, it is still an important and increasingly significant consideration in both migration and health policy.

Limitations and opportunities
To limit bias, this study used a priori protocol and a double-blinded approach for study selection and quality appraisal. The inclusion of only English and German papers published in academic journals may have contributed to selection bias and there is always a risk despite a thorough search strategy that articles were missed however, this risk was Reporting ambiguity within included studies may have led to over or underestimation of methodological quality. Caution is needed in interpreting these studies because secondary data were often used with other objectives and because some studies used small sample groups (especially qualitative case studies) with findings that could not be generalized to larger groups. Five studies did not fit within the MMAT categorisation (modelling studies) and were therefore not assessed for quality, which remains a limitation of this review. This study attempted to introduce systems thinking in fields of research that are still siloed. The inclusion of all three elements of the climate-migration-health nexus was required for inclusion, some studies still focused on a 'dyad' within the nexus, with an element at times underexplored requiring interpretation in the extraction phase. Some eligible studies suggested potential links to climate change rather than demonstrate the link with climate data. This may have led to an overestimation of the relationship between the mobility response and health outcomes and climate change and also capture climate variability and other forms of environmental change, which would be challenging if not impossible to set apart as an exposure in this SLR.

Future research directions
The recommendations extracted, analysed and synthesized in this review pertained mainly to rural livelihoods revealing a potential gap in researching this nexus in urban settings. The research focussed on mobile populations and less so on the entire migration ecosystem including sending and host communities echoing a call for research on climate mobilities to shift part of its focus from climate-sensitive sending areas to destination areas (Boas et al, 2019). Further, there was a focus on adaptation with less attention paid to mitigation activities. It may be worthwhile looking at these concepts together, or on a spectrum whereby adaptation activities can play a role in mitigation and vice versa. There was very little to no reference to conflict in these studies although we know that conflict and migration are both related socially mediated, tertiary impacts of climate change and likely to be playing a role in some of these settings, and influencing health and health resources.
Finally, the included studies focused on agricultural climate change adaptation with less attention paid to infrastructure and health.

CONCLUSION
As climate change continues to shape patterns and scales of human migration, policy makers are challenged to make evidence-based decisions that enable competent governance of orderly, safe, regular and humane migration, that safeguards human health and wellbeing. This review identified, analysed and synthesized what is known to date from research investigating the climate change, migration and health nexus. The findings largely confirm principles of good migration governance; that the universal promotion of migration should be avoided because it is not always adaptive, that forced migration should be prevented and that mobile populations should be supported in their decision-making. Some elements of our current understanding are reinforced in terms of the need to favour community-led approaches, provide durable solutions, preserve cultural ties and to enable migrant participation because it has the potential to maximise benefit for all those affected by mobility responses. This review also draws attention to more novel discussions such as non-economic loss and damages arising from climate change that include health impacts.
The included studies focussed on adaptation without mention of the role of mitigation, or adaptive responses that also mitigate climate change. Revealing an area where the climate, migration and health community may want to take a stand, in the spirit of true prevention.
The research also focussed on rural rather than urban settings and agriculture and less so health. Yet the policy recommendations synthesized by this review still call for the provision of basic prerequisites for health, a focus on health equity, and access to health care, reiterating that these fundamental requirements for health are not a reality for all. In sum, the results call for transformative policies that support the health and wellbeing of people engaging in, and affected by mobility responses, including those whose migration decisions and experiences are influenced by climate change, and to establish and develop inclusive migrant healthcare. Funding: This research received no external funding.