Types of migration
Quantifying environmental migration is challenging given the multiple drivers of such movement, related methodological challenges and the lack of data collection standards. Some quantitative data exist on population displacement within a country, and to a lesser degree across borders, due to natural hazards. However, for migration due to slow-onset environmental processes, such as drought or sea-level rise, most existing data are qualitative and based on case studies, with few comparative studies. While data gaps persist, research methodologies are constantly being improved.
Some key terms are important in the context of migration and environmental and climatic changes:
Among the total of 46.9 million new internal displacements registered in 2023, 56 per cent were triggered by disasters (IDMC, 2024). As of 31 December 2023, at least 7.7 million people in 82 countries and territories were living in internal displacement as a result of disasters that happened not only in 2023, but also in previous years (ibid.). This is an 11 per cent decrease in the total number of internally displaced persons (IDPs) due to disasters compared to 2022 (ibid.). Disaster displacement in 2023 was the third highest figure in the last decade, even though there were one third fewer displacements due to weather-related hazards, partly resulting from La Niña’s end and El Niño’s onset.
The top 5 countries with the highest number of new internal displacements due to disasters in 2023 were China (4.7 million), Türkiye (4.1 million), Philippines (2.6 million), Somalia (2 million), Bangladesh (1.8 million) (ibid.).
77 per cent of the 26.4 million new internal disaster displacements in 2023 were the result of weather-related hazards such as storms, floods and droughts (ibid.). Floods remained the hazard displacing most people, causing 9.8 million internal displacements, closely followed closely by storms, causing 9.5 million internal displacements (ibid.). Almost a quarter of all internal displacements were due to earthquakes, especially those in Türkiye, Syria, the Philippines, Afghanistan and Morocco. In 2023 earthquakes and volcanic activity caused he same number of displacements as the total of the previous seven years (ibid.). Some of these earthquakes struck areas where displaced persons from conflict were already living, e.g. in Syria and Afghanistan (ibid.).
The impact of the COVID-19 pandemic continues to affect internally displaced persons around the world, particularly from the loss of livelihoods and food insecurity (IDMC 2021; IDMC 2022; IDMC 2023). In addition, climate change is changing precipitation and temperature patterns and increasing the frequency and severity of extreme weather events in many parts of the world, all of which affect food security by reducing agricultural production (IPCC, 2022), causing people to move seasonally or permanently from at-risk areas. Read more about climate change, food security and human mobility here.
The Intergovernmental Panel on Climate Change (IPCC)projects that more than one billion people globally could be exposed to coastal-specific climate hazards by 2050, potentially driving tens to hundreds of millions of people to leave their home in coming decades (IOM, 2022; IPCC, 2022),
Slow-onset processes such as droughts or sea level rise also increasingly affect people’s mobility worldwide. In this regard, the World Bank’s Groundswell report projects that climate change could lead up to 216 million people across six world regions (Sub-Saharan Africa, South Asia, Latin America, East Asia and the Pacific, North Africa, Eastern Europe and Central Asia) to move within their countries by 2050 if no urgent action to reduce global greenhouse gas emissions is taken (Clement et al. 2021).
Comprehensive datasets on environmental migration or planned relocation do not yet exist at the global level, but several initiatives have started to collect information across several countries. The following list provides an overview of the available information, including more qualitative research.
Primary data collection:
National authorities collect information on displacement and evacuations linked to disasters, in particular fast onset ones. Local-level disaster displacement data are available from (international and national) humanitarian agencies (NGOs, UN agencies) engaged in relief operations, which collect data in order to respond to the needs of affected populations. Planned relocation of communities in the context of environmental and climate change is increasingly implemented by governments. For a summary of relocation programmes, see Ionesco, Mokhnacheva and Gemenne, 2016; Benton, 2017 and Georgetown University, UNHCR and IOM, 2017).
Administrative data sources, such as the numbers of humanitarian visas (such as in the US, Brazil, Ecuador or Mexico) or residence permits granted (for instance, by Argentina) linked to disasters, can provide information on cross-border displacement and movements in the context of environmental events more generally.
IOM’s Displacement Tracking Matrix (DTM) is a system used to track and monitor disaster displacement and population mobility. Data, which can be disaggregated by gender and sex, are regularly captured, processed and disseminated to provide a better understanding of the movements and evolving needs of displaced populations and migrants, whether in situ or en route, before, during and in the aftermath of disasters. The data are presented in the DTM Data Portal. A study on how current DTM practices collect data on human mobility in the context of environmental degradation, climate change and disasters and draws also provides recommendations on how to improve current tools and practices. Recommendations include improving the focus of some DTM questions and increasing the amount of options available for respondents to provide more granular data on the migration, environment and climate nexus (IOM, 2020).
DTM’s Transhumance Tracking Tool (TTT) is a tool developed by IOM to track transhumance movements and collect alerts related to agro-pastoral conflicts, in order to prevent and mitigate them.
Innovative data sources include mobile phone-based sources such as call detail records (CDRs). Big data generated by mobile phone users before and after disasters, such as the 2010 earthquake in Haiti (Bengtsson et al., 2011) and several typhoons in the Philippines and Bangladesh (Lu et al., 2016), can indicate where displaced persons moved to and help deliver prompt and targeted humanitarian assistance or to understand internal movements (Laczko and Rango, 2014; GMG, 2017). This can be a means to collect complementary quantitative data on movements at small-scale and on seasonal patterns linked to adaptation to environmental change and disasters that are difficult to account for in traditional household survey tools (Lu et al., 2016). Other projects aim at using big data sources, such as satellite images or social media data, to identify early the environmental stressors that could lead to displacement (see for instance Isaacman et al., 2017).
Several research projects have and are collecting new data on the links between the environment and human mobility, but few with a comparative approach. There are three notable exceptions. First, the Migration, Environment and Climate Change: Evidence for Policy (MECLEP) project, implemented by IOM and six research partners in 2014-2017, and funded by the EU, conducted a comparative quantitative and qualitative study of six countries (Dominican Republic, Haiti, Kenya, Papua New Guinea, Mauritius and Viet Nam). The methodology developed for the project could easily be applied to other countries.
Second, the Pacific Climate Change and Migration (PCCM) project by ILO, UNESCAP and UNDP focused on Tuvalu, Nauru and Kiribati. The United Nations University Institute for Environment and Human Security (UNU-EHS) released findings detailing how climatic changes are impacting these Pacific island states.
Third, the HABITABLE project is a EU-funded project (2020-2024) aiming at significantly advancing our understanding of the current interlinkages between climate impacts and migration and displacement patterns, and to better anticipate their future evolution. Led by the Hugo Observatory, the project brings together 21 partners from 18 countries and focuses on four regions: West Africa, East Africa, Southern Africa and South-East Asia.
Secondary data sources and research:
The Internal Displacement Monitoring Centre (IDMC) has compiled data on internal displacement in the context of disasters since 2008 globally through its online Global Internal Displacement Database (GIDD). The estimates are based on information by national authorities, UN agencies such as IOM, the International Federation of the Red Cross (IFRC) and the UN Office for the Coordination of Humanitarian Affairs (OCHA), non-governmental organizations and in particular media reports. Figures are published in the annual Global Report on Displacement (GRID), which also covers internal displacement due to conflict and violence. IDMC is developing methodologies to map and assess future disaster displacement risks and is starting to gather data on cross-border displacement.
The HELIX project (High-End Climate Impacts and Extremes) provided research on climate impacts and adaptation in relation to varying global warming scenarios (2, 4 and 6 degrees Celsius), using predictive analytics. Human migration was included in the impact studies. The recent Groundswell: Preparing for internal climate migration report (Rigaud et al., 2018) developed a model for future population distribution in 2050 in three regions (sub-Saharan Africa, South Asia and Latin America) if no action is taken.
The CLIMIG database of studies on environmental migration, both of qualitative and quantitative nature, was developed by the University of Neuchatel (Switzerland).
The Environmental Migration Portal by IOM, features a searchable research database, initially based on the People on the Move in a Changing Climate: A Bibliography, published by IOM in collaboration with University of Neuchatel. The database also includes migration and environment country assessments published by IOM.
The thematic working group on “Environmental change and migration” of the Global Knowledge Partnership on Migration and Development (KNOMAD) produced an annotated bibliography on Environmental Migration and developed a toolkit on planned relocation with many case study examples (Georgetown University, UNHCR and IOM, 2017).
The first “Atlas on Environmental Migration” was produced by IOM and Sciences Po, Paris (published with Routledge in 2017). The publication brings together, for the first time, existing knowledge on the links between migration and environmental change, presented through comprehensive maps, diagrams and case studies.
The Hugo Observatory at the University of Liège (Belgium) focuses on research on environmental changes and Migration.
The Platform on Disaster Displacement (a follow-up to the Nansen Initiative) provides a global dataset including preliminary findings from over 400 planned relocation cases. Last updated in 2021, it features characteristics including geographic location, spatial pattern, primary hazard and completion status.
IOM GDI’s interactive Climate Mobility Impacts dashboard visualizes where hazard exposure, high population density, and economic vulnerability are projected to coincide in future. These data help identify hotspots sensitive to heatwaves, river floods, drought, wildfire, tropical cyclone and crop failure, and users can map hazards regionally and under two climate warming scenarios and three socio-economic scenarios. These data can also develop effective anticipatory action to support at-risk communities worldwide.
The CLIMB database contains policy and legal instruments and practices addressing human mobility in the context of the adverse effects of climate change, disasters, and environmental degradation. The tool provides a resource for policymakers as well as researchers, practitioners and other stakeholders working in the area of policy development on human mobility, disasters, climate change, and environmental degradation.
Over the past decade, important advances in methodologies and data collection have been made. Academic researchers and specialized agencies are working on improved methodologies for comparative cross-country or cross-region studies, agent-based models and multi-factor simulators designed to predict future trends (such as drought-induced displacement modelling, Ginnetti and Franck, 2014, or IDMC’s Global Displacement Risk Model focused on sudden-onset disasters based on housing destructions), and hotspot identification triangulating environmental and social data, all of which can contribute greatly to improving current evidence and future projections of environmental migration trends so as to better inform policies and action.
Innovative data sources: Big data can provide opportunities that can further be strengthened in trying to estimate the extent of movements in contexts of disasters and degrading environments. These new methods can fill gaps in time series data, indicate where people have moved from and to and enhance the timeliness of this information. In some cases, these new methods could be used to inform life-saving early warnings. At the same time, privacy safeguards and ethical considerations need to be adhered to.
Nonetheless, difficulties remain.
Human Mobility in the context of Environmental and Climate Change: Assessing current and recommended practices for analysis within DTM. IOM. Geneva, Switzerland.
International Organization for Migration, Eurasylum
Disaster Displacement: A global review, 2008-2018. Internal Displacement Monitoring Centre (IDMC), Geneva, Switzerland.
“Systematic data collection and monitoring of displacement and its impacts at local, national, regional and international level to inform comprehensive needs and risk assessments for the formulation of policy and plans.” Summary Report, Implementation of the Workplan of the Task Force on Displacement under the Warsaw International Mechanism for Loss and Damage (WIM) United Nations Framework Convention on Climate Change (UNFCCC), May
Internal Displacement Index 2020 Report. IDMC, Geneva.
2022
2023
2024
GRID 2022: Global Report on Internal Displacement. IDMC, Geneva.
GRID 2023: Global Report on Internal Displacement. IDMC, Geneva.
GRID 2024: Global Report on Internal Displacement. IDMC, Geneva.
Foresight
Handbook for Improving the Production and Use of Migration Data for Development. KNOMAD, World Bank, Washington, DC.
Compendium of IOM Activities on Disaster Risk Reduction and Resilience. IOM, Geneva.
Thinking about Tomorrow, Acting Today: The Future of Climate Mobility. IOM, Geneva.
“How useful and reliable are disaster databases in the context of climate and global change? A comparative case study analysis in Peru.” In: Natural Hazards and Earth Systems Sciences, pp. 475.
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