A finer picture of global migration reveals complex patterns

While public discussions often focus on climate change driving people to emigrate, new research published in Nature Human Behaviour shows that net-migration patterns around the world are more strongly linked with socioeconomic factors. The study also provides a new, high-resolution dataset of net-migration over the past two decades to inform policymaking and fuel further research. The new dataset is openly available and can be easily explored through an online interactive map.

The research group, which included researchers from IIASA, Aalto University, and the University of Bologna, published similar research last year covering the period 1990-2000. The new analysis covers the past two decades, 2000-2019. The high-resolution dataset they prepared makes it possible to answer questions that can’t be addressed with coarser data, such as national averages.

“There was a real need for a dataset like this, but it didn’t exist. So, we decided to make it ourselves,” notes study lead author Venla Niva, a postdoctoral researcher at Aalto University.

The team combined birth and death rates with overall population growth to estimate net migration. The role of socioeconomics and climate were incorporated through the Human Development Index (HDI) and the aridity index. By starting with sub-national death and birth ratios and scaling them down to 10 km resolution, the researchers produced a net-migration dataset of unprecedented resolution. This makes it possible to address questions that can’t be answered using national aggregates.

"The annual gridded migration data we produced can be useful to answer many relevant research questions such as climate-related migration and migration trends. The migration data can be combined with gridded environmental and socioeconomic data enabling comprehensive analysis of migration drivers," says study coauthor Raya Muttarak, a researcher in the IIASA Population and Just Societies Program and at the University of Bologna.

The researchers found high levels of emigration in regions that were on the middle of the scale in terms of both HDI and aridity, such as areas in Central America, northeast Brazil, Central Africa, and southeast Asia. This indicates that it is not the poorest of the poor who are fleeing environmental disasters or environmental changes, which points to migration as an adaptation method used by people who have the capacity to move.

“This finding is consistent with our previous work where we performed meta-analysis of quantitative studies on environmental migration and found that migration response to environmental stress is more likely in middle-income countries,” explains Muttarak.

By the same token, areas with a high HDI experienced positive net migration regardless of their climate condition. For example, regions in the Arabian Peninsula, North America, Australia, and the North Mediterranean are net receivers despite their aridity.

“Decision makers should pay attention to this. Rather than focusing solely on border closures and combatting migration, we should work to support and empower individuals in economically disadvantaged countries. That would help reduce the drivers that compel people to migrate in search of better opportunities,” says Matti Kummu, associate professor of global water and food issues at Aalto University and senior author of the study.

The granularity of the new dataset reveals complexities in migration patterns that are hidden when national data is used. In France and Italy, for example, the study revealed interesting differences between north and south, and in Spain there is an east-west difference.

Unexpected patterns also showed up in urban-rural migration. According to the researchers it is commonly believed that urban areas pull people from rural areas, but that wasn't the case everywhere. There are in fact a lot of places, for example, in Europe, where the opposite is true. Migration from cities to rural areas was also evident in parts of Congo, Indonesia, Pakistan, and Venezuela and when the analysis is done on the level of communities, the picture becomes even more complex.

“Data on migration is often not available or difficult to compare across countries. Our findings help provide a more complete picture of migration, allowing us to quantify and assess the impact of migration at a fine level detail across all countries of the world,” says IIASA researcher Guy Abel, a coauthor also associated with the Asian Demographic Research Institute at Shanghai University. 

Researchers can use the new dataset to understand migration more precisely than through national averages, which don’t capture the whole story. The team has already shared the data with other researchers and international organizations such as the UN International Organization for Migration. The interactive map is available for interested people to explore these patterns for themselves.

Adapted from a press release prepared by Aalto University.

Reference

Niva, V., Horton, A., Virkki, V., Heino, M., Kosonen, M., Kallio, M., Kinnunen, P., Abel, G.J., Muttarak, R., Taka, M., Varis, O., & Kummu, M. (2023). World’s human migration patterns in 2000–2019 unveiled by high-resolution data. Nature Human Behaviour DOI: 10.1038/s41562-023-01689-4