Empirical research on international environmental migration: a systematic review

Understanding the global subnational migration patterns driven by hydrological intrusion exposure

Amid the escalating global climatic challenges, hydrological risks significantly influence human settlement patterns, underscoring the imperative for an in-depth comprehension of hydrological change's ramifications on human migration. However, predominant research has been circumscribed to the national level. The study delves into the nonlinear effects of hydrological risks on migration dynamics in 46,776 global subnational units. Meanwhile, leveraging remote sensing, we procured globally consistent metrics of hydrological intrusion exposure, offering a holistic risk assessment encompassing hazard, exposure, and vulnerability dimensions, thus complementing previous work. Here, we show that exposure is the primary migration driver, surpassing socioeconomic factors. Surrounding disparities further intensified exposure's impact. Vulnerable groups, especially the economically disadvantaged and elderly, tend to remain in high-risk areas, with the former predominantly migrating within proximate vicinities. The nonlinear analysis delineates an S-shaped trajectory for hydrological exposure, transitioning from resistance to migration and culminating in entrapment, revealing dependence on settlement resilience and adaptability.

How do environmental stressors influence migration? A meta-regression analysis of environmental migration literature

BACKGROUND

The amount of literature on environmental migration is increasing. However, existing studies exhibit contradictory results. A systematic synthesis of the environment-migration relationship is much needed.

OBJECTIVE

This study summarizes research findings, calculates the effect sizes of environmental stressors, identifies publication bias, and investigates heterogeneous environmental effects on migration.

METHODS

We collected 3,380 estimates from 128 studies published between 2000 and 2020 to explore the environment-migration relationship and performed weighted instrumental variable regression to unveil the heterogeneous environmental effects on out- and net migration.

RESULTS

The majority of environmental stressors were not important predictors of out- and net migration. Among the results showing environmental impacts on migration, 58% and 68% reported that environmental stressors increased out- and net migration, respectively, while 58% reported that environmental stressors decreased in-migration. The overall environmental impact on migration was small; however, disaster-related stressors showed a medium effect, and rapid-onset stressors had a stronger impact than slow-onset ones. Multivariate meta-regression analyses demonstrated that environmental stressors were more likely to trigger internal migration than international migration and that developed countries were less likely to experience out-migration. Rapid-onset environmental stressors did not increase out-migration but played an important role in decreasing net migration toward environmentally stressed areas. Meanwhile, we also found a publication bias toward studies showing a positive relationship between environmental stressors and migration in the previous environmental migration literature.

CONCLUSIONS

Environmental stressors may affect migration; however, the environmental effect depends on migration measurements, environmental stressors' forces and rapidity, and the context in which migration takes place.

CONTRIBUTION

This study contributes to migration studies by synthesizing and validating the environment-migration relationship and enhancing our understanding of how and under what circumstances environmental stressors may affect migration.

Compelled and constrained migration: restrictions to migration agency in the Marshall Islands

Migration as adaptation implies agency, yet environmental and non-environmental factors and their interactions may limit the availability of adaptation options, including migration. This study investigates migration agency in the Marshall Islands, particularly the role of geographic isolation and climate change. Interviews with internal migrants living in Majuro and members of government and civil society reveal how social, economic, cultural, and environmental factors shape migration contexts. Results suggest that geographic isolation-related factors may increase likelihoods of simultaneously more compelled and more constrained moves, particularly as climate change impacts increase. Climate change-related impacts on resource-dependent livelihoods may compel migration in search of new economic opportunities. However, worsening environmental conditions may also exacerbate cost-related migration constraints by reducing the resources available to support migration.

Do Resettled People Adapt to Their Current Geographical Environment? Evidence from Poverty-Stricken Areas of Northwest Yunnan Province, China

The geographical environment adaptation of the resettled population is a deep-seated problem that determines whether the goal of the poverty alleviation resettlement (PAR) policy can be achieved. Scientific assessment of adaptive capacity (AC) and adaptation level (AL) provides a basis for subsequent policy formulation, which is of practical significance. This study took the poverty-stricken areas of northwest Yunnan as the study area and calculated the adaptive capacity index (ACI) and adaptation level index (ALI) based on survey data of 1002 resettled households and regional socioeconomic statistics by constructing the vulnerability as expected poverty (VEP) model and multi-factor analysis model. The results showed that (1) The ACI and ALI were 0.660 and 61.2 respectively, indicating that the resettled population has obvious environment adaptation barriers and a relatively high risk of returning to poverty. (2) The AC and AL of the resettled population had significant geographical differentiation. In general, Diqing Prefecture was significantly better than Nujiang Prefecture and the problems in Gongshan County, Fugong County and Lanping County were more prominent. (3) AC is a determinant of AL. However, these two indices in Gongshan and Lanping counties deviated from the general trend due to different policy effects. Based on the evaluation results and differentiation mechanism analysis, the study finally emphasized the importance of formulating and implementing the follow-up development plan of the resettled population and put forward measures to promote the resettled population to adapt to the geographical environment around the three core tasks of employment income increase, public service and bottom guarantee.

Green place rather than green space as a health determinant: A 20-year scoping review

Numerous scientific studies, applying different approaches, have provided evidence of the links between the environment and people's health. Green spaces have been the subject of research aimed at exploring their benefits as components of the urban environment. We investigated possible causal relationships between green spaces and health, with the aim of addressing the following question. Does the mere material presence of green spaces contribute to the health of people who live in its vicinity, or are the health-promoting qualities of green spaces attributed to the ability of people to actually see, access, and enjoy them? The latter view highlights the relational dimension of places, and it entails personal relationships with places which are imbued with psychological meaning and significance for those who visit and experience them. We reviewed relevant literature, comprising a total of 189 papers on this topic that have been published over the first two decades of this century. Our findings showed that the material aspects of green spaces, such as their abundance and proximity to residences, received much more attention in studies than their quality and characteristics. However, relational rather than material measures of green spaces demonstrated statistically greater positive impacts of green spaces on health. These findings indicate that both sensory stimuli and activities and feelings attached to green spaces are essential for better health outcomes. Incorporating a relational perspective of green place-thinking into the existing literature on green spaces and health could contribute to optimizing the positive effects of green spaces and thus to the creation of healthy and livable cities.

Anticipating sea-level rise and human migration: A review of empirical evidence and avenues for future research

Sea-level rise (SLR) threatens millions of people living in coastal areas through permanent inundation and other SLR-related hazards. Migration is one way for people to adapt to these coastal changes, but presents an enormous policy challenge given the number of people affected. Knowledge about the relationship between SLR-related hazards and migration is therefore important to allow for anticipatory policymaking. In recent years, an increasing number of empirical studies have investigated, using survey or census data, how SLR-related hazards including flooding, salinization, and erosion together with non-environmental factors influence migration behavior. In this article, we provide a systematic literature review of this empirical work. Our review findings indicate that flooding is not necessarily associated with increased migration. Severe flood events even tend to decrease long-term migration in developing countries, although more research is needed to better understand the underpinnings of this finding. Salinization and erosion do generally lead to migration, but the number of studies is sparse. Several non-environmental factors including wealth and place attachment influence migration alongside SLR-related hazards. Based on the review, we propose a research agenda by outlining knowledge gaps and promising avenues for future research on this topic. Promising research avenues include using behavioral experiments to investigate migration behavior under future SLR scenarios, studying migration among other adaptation strategies, and complementing empirical research with dynamic migration modeling. We conclude that more empirical research on the SLR-migration nexus is needed to properly understand and anticipate the complex dynamics of migration under SLR, and to design adequate policy responses. This article is categorized under: Climate Economics < Aggregation Techniques for Impacts and Mitigation CostsVulnerability and Adaptation to Climate Change < Learning from Cases and AnalogiesAssessing Impacts of Climate Change < Evaluating Future Impacts of Climate Change.

A bibliometric review on the drivers of environmental migration

A large body of literature exists arguing that numerous, complex factors result in environmental migration. Thus, in order to understand environmental migration, we must investigate how its drivers are defined, explained and interrelated. This study aims to produce a comprehensive analysis of the literature on the drivers of environmental migration and assess future opportunities for studying 'environmental migration'. We conduct a systematic literature search using the keywords 'environmental migration' and 'drivers' in Scopus and Web of Knowledge, analysing 146 publications. The findings are organised as a bibliometric analysis, including network analysis and evaluation of publication metrics. Results show that the literature on environmental migration drivers constitutes a relatively new, growing field largely developed in the USA. It is rooted in the wider environmental migration literature and strongly associated with the discourse of climate change impacts as driving factors. Typologies of 'migrants' are more prevalent than 'refugees' when referring to actors.

Environmental Displacement and Mental Well-Being in Banjarnegara, Indonesia

BACKGROUND

Residential moves (displacement) owing to climate- and weather-related disasters may significantly impact mental health. Despite the growing risk from climate change, health impacts of environmental-mobility remain understudied.

OBJECTIVES

We assessed the effects of displacement on the association between landslides and changes in perceived mental well-being in Banjarnegara, Indonesia. We also investigated whether sociodemographics (age, sex, level of education, household-level income, or employment in agriculture) and landslide characteristics (number and severity of landslides) were associated with differing odds of relocation after experiencing landslides.

METHODS

In this cross-sectional study, we surveyed 420 individuals who experienced landslides between 2014 and 2018 to assess perceived changes in mental well-being, comparing after landslide exposure to before landslide exposure. We used a novel six-item measure that was created in collaboration with the local community to compare perceived changes between those who were displaced by landslides and those who were not displaced, using logistic and multinomial regressions adjusted for sociodemographic characteristics. We then assessed whether the odds of displacement differed based on sociodemographic characteristics and landslide exposure characteristics, using logistic regressions.

RESULTS

Those who were displaced were more likely than those who were not displaced to report perceived increases in economic stability [odds ratio (OR)=3.06; 95% confidence interval (CI): 1.45, 6.46], optimism (OR=4.01; 95% CI: 1.87, 8.61), safety (OR=2.71; 95% CI: 1.44, 5.10), religiosity (OR=1.92; 95% CI: 1.03, 3.65), and closeness with community (OR=1.90; 95% CI: 1.10, 3.33) after landslides compared with before their first landslide during the study period. More frequent landslide exposures were associated with reduced odds of relocation, but more severe landslides were associated with increased odds of relocation.

DISCUSSION

These findings suggest that landslides affect the mental well-being not only of those who are displaced but also of those who are left behind. Further, this work supports the need for community-based participatory research to fully capture the health impacts of environmental mobility. https://doi.org/10.1289/EHP9391.

The role of migration and demographic change in small island futures

Low-lying atoll islands are especially threatened by anticipated sea-level rise, and migration is often mentioned as a potential response of these island societies. Further, small island states are developing population, economic and adaptation policies to plan the future. Policies, such as raising of islands or land reclamation, require a long-term vision on populations and migration. However, population and migration systems in small island settings are poorly understood. To address this deficiency requires an approach that considers changing environmental and socio-economic factors and individual migration decision-making. This article introduces the conceptual model of migration and explores migration within one small island nation, the Maldives, as an example. Agent-based simulations of internal migration from 1985–2014 are used as a basis to explore a range of potential demographic futures up to 2050. The simulations consider a set of consistent demographic, environmental, policy and international migration narratives, which describe a range of key uncertainties. The capital island Malé has experienced significant population growth over the last decades, growing from around 67,000 to 153,000 inhabitants from 2000 to 2014, and comprising about 38 percent of the national population in 2014. In all future narratives, which consider possible demographic, governance, environmental and globalization changes, the growth of Malé continues while many other islands are effectively abandoned. The analysis suggests that migration in the Maldives has a strong inertia, and radical change to the environmental and/or socio-economic drivers would be needed for existing trends to change. Findings from this study may have implications for national development and planning for climate change more widely in island nations.

The Differential Influence of Geographic Isolation on Environmental Migration: A Study of Internal Migration Amidst Degrading Conditions in the Central Pacific

This study investigates how geographic isolation interacts with declining environmental and economic conditions in Kiribati, an island nation wherein which limited access to financial resources amidst degrading environmental conditions potentially constrain capital-intensive, long distance migration. We examine whether geographic isolation modifies the tenets of two dominant environmental migration theses. The environmental scarcity thesis suggests that environmental degradation prompts migration by urging households to reallocate labor to new environments. In contrast, the environmental capital thesis asserts that declining natural resource availability restricts capital necessary for migration. Results show that the commonly applied environmental scarcity thesis is less valid and the environmental capital thesis is more relevant in geographically isolated places. Findings indicate that geographic isolation is an important dimension along which migration differences emerge. As overall environmental and economic conditions worsen, likelihoods of out-migration from less remote islands increase whereas likelihoods of out-migration from more isolated islands decrease.

Assessment of the Nutritional Status, Diet and Intestinal Parasites in Hosted Saharawi Children

Since the early 1990s, Spanish humanitarian associations have welcomed Saharawi children from the refugee camps in Tindouf (Argelia). These children are the most affected by the lack of food, water, hygienic measures and health care. The main objective of this study was to analyze the anthropometric, nutritional and parasitological data of 38 Saharawi boys and girls (from 10 to 13 years old) under a holiday host program in the city of Valencia. Our results confirm that malnutrition and multiparasitism are highly frequent, so it is understood that living conditions in refugee camps continue to be precarious with a lack of proper hygiene and nutrition. Furthermore, biochemical alterations, lactose malabsorption and the risk of celiac disease, also detected in our study as a secondary objective, will complicate nutritional management and restoration of health. For this reason, sustainable feeding alternatives and interventions from a hygienic and nutritional point of view are proposed, emphasizing in an improvement in the education of parents and children.

Exploring Connections—Environmental Change, Food Security and Violence as Drivers of Migration—A Critical Review of Research

Migration, whether triggered by single events, such as violent conflict, or by long term pressures related to environmental change or food insecurity is altering sustainable development in societies. Although there is a large amount of literature, there is a gap for consolidating frameworks of migration-related to the interaction and correlation between drivers. We review scientific papers and research reports about three categories of drivers: Environmental Change (EC), Food Security (FS), and Violent Conflict (VC). First, we organize the literature to understand the explanations of the three drivers on migration individually, as well as the interactions among each other. Secondly, we analyse the literature produced regarding Colombia, Myanmar, and Tanzania; countries with different combinations of the driving factors for migration. Although we find that many correlations are explained in the literature, migration is mostly driven by structural vulnerabilities and unsustainable development paths in places that have a low resilience capacity to cope with risk. For example, food insecurity, as a product of environmental changes (droughts and floods), is seen as a mediating factor detonating violent conflict and migration in vulnerable populations. The paper contributes to the literature about multi-driven migration, presenting an overview of the way in which different driver combinations trigger migration. This is important for determining the best governance mechanisms and policy responses that tackle forced migration and improve the resilience of vulnerable communities as well as sustainable development.

Migration, Remittances, and Forest Cover Change in Rural Guatemala and Chiapas, Mexico

This article investigates how migration and remittances affect forest cover in eight rural communities in Guatemala and Chiapas, Mexico. Based on household surveys and remote sensing data, we found little evidence to support the widespread claim that migration takes pressure off forests. In the Chiapas sites, we observed no significant changes in forest cover since 1990, while in the Guatemalan sites, migration may have increased demand for agricultural land, leading to an average annual forest loss of 0.73% during the first decade of the millennium. We suggest that when attractive opportunities exist to invest in agriculture and land expansion, remittances and returnee savings provide fresh capital that is likely to increase pressure on forests. Our study also has implications for the understanding of migration flows; in particular, migration has not implied an exodus out of agriculture for the remaining household members nor for the returning migrants. On the contrary, returning migrants are more likely to be involved in farming activities after their return than they were before leaving.

Climate Change Adaptation Options for Coastal Communities and Local Governments

Extreme weather events and failure to adapt to the likely impacts of climate change are two of the most significant threats to humanity. Therefore, many local communities are preparing adaptation plans. Even so, much of what was done has not been published in the peer-reviewed literature. This means that consideration of adaptation options for local communities is limited. With the objective of assisting in the development of adaptation plans, we present 80 adaptation options suitable for coastal communities that can be applied by local governments. They are a catena of options from defend to co-exist and finally, retreat that progresses as impacts become less manageable. Options are organized according to their capacity to protect local properties and infrastructure, natural systems, food production, availability of fresh and drinking water and well-being of the local population, as these are likely to be affected by climate change. To respond to multiple threats, ‘soft’ options, such as awareness raising, planning, political articulation and financial incentives, insurance and professional skills enhancement, can be encouraged immediately at relatively low cost and are reversible. For specific threats, options emphasize change in management practices as pre-emptive measures. Key audiences for this work are communities and local governments starting to consider priority actions to respond to climate change impacts.

Border and Migration Controls and Migrant Precarity in the Context of Climate Change

Climate change impacts natural and human systems, including migration patterns. But isolating climate change as the driver of migration oversimplifies a complex and multicausal phenomenon. This article brings together the literature on global migration and displacement, environmental migration, vulnerability and precarity, and borders and migration governance to examine the ways in which climate-induced migrants experience precarity in transit. Specifically, it assesses the literature on the ways in which states create or amplify precarity in multiple ways: through the use of categories, by externalizing borders, and through investments in border infrastructures. Overall, the paper suggests that given the shift from governance regimes purportedly based on protection and facilitation to regimes based on security, deterrence, and enforcement, borders are complicit in producing and amplifying the vulnerability of migrants. The phenomenon of climate migration is particularly explicative in demonstrating how these regimes, which categorize individuals based on why they move, are and will continue to be unable to manage future migration flows.

Climate Change and the Neglected Tropical Diseases

Climate change is expected to impact across every domain of society, including health. The majority of the world's population is susceptible to pathological, infectious disease whose life cycles are sensitive to environmental factors across different physical phases including air, water and soil. Nearly all so-called neglected tropical diseases (NTDs) fall into this category, meaning that future geographic patterns of transmission of dozens of infections are likely to be affected by climate change over the short (seasonal), medium (annual) and long (decadal) term. This review offers an introduction into the terms and processes deployed in modelling climate change and reviews the state of the art in terms of research into how climate change may affect future transmission of NTDs. The 34 infections included in this chapter are drawn from the WHO NTD list and the WHO blueprint list of priority diseases. For the majority of infections, some evidence is available of which environmental factors contribute to the population biology of parasites, vectors and zoonotic hosts. There is a general paucity of published research on the potential effects of decadal climate change, with some exceptions, mainly in vector-borne diseases.

Neglected Tropical Disease Control - The Case for Adaptive, Location-specific Solutions

The world is experiencing environmental and social change at an unprecedented rate, with the effects being felt at local, regional, and international scales. This phenomenon may disrupt interventions against neglected tropical diseases (NTDs) that operate on the basis of linear scaling and 'one-size-fits-all'. Here we argue that investment in field-based data collection and building modelling capacity is required; that it is important to consider unintended consequences of interventions; that inferences can be drawn from wildlife ecology; and that interventions should become more location-specific. Collectively, these ideas underpin the development of adaptive decision-support tools that are sufficiently flexible to address emerging issues within the Anthropocene.

Urban governance and the systems approaches to health-environment co-benefits in cities

The term "co-benefits" refers to positive outcomes accruing from a policy beyond the intended outcome, often or usually in other sectors. In the urban context, policies implemented in particular sectors (such as transport, energy or waste) often generate multiple co-benefits in other areas. Such benefits may be related to the reduction of local or global environmental impacts and also extend into the area of public health. A key to identifying and realising co-benefits is the adoption of systems approaches to understand inter-sectoral linkages and, in particular, the translation of this understanding to improved sector-specific and city governance. This paper reviews a range of policies which can yield health and climate co-benefits across different urban sectors and illustrates, through a series of cases, how taking a systems approach can lead to innovations in urban governance which aid the development of healthy and sustainable cities.

Country-Specific Effects of Climate Variability on Human Migration

Involuntary human migration is among the social outcomes of greatest concern in the current era of global climate change. Responding to this concern, a growing number of studies have investigated the consequences of short to medium-term climate variability for human migration using demographic and econometric approaches. These studies have provided important insights, but at the same time have been significantly limited by lack of expertise in the use of climate data, access to cross-national data on migration, and attention to model specification. To address these limitations, we link data on internal and international migration over a 6-year period from 9,812 origin households in Kenya, Uganda, Nigeria, Burkina Faso and Senegal to high-resolution gridded climate data from both station and satellite sources. Analyses of these data using several plausible specifications reveal that climate variability has country-specific effects on migration: Migration tends to increase with temperature anomalies in Uganda, tends to decrease with temperature anomalies in Kenya and Burkina Faso, and shows no consistent relationship with temperature in Nigeria and Senegal. Consistent with previous studies, precipitation shows weak and inconsistent relationships with migration across countries. These results challenge generalizing narratives that foresee a consistent migratory response to climate change across the globe.