Global migration patterns mapped

Net migration

This map shows country-specific net migration: blue marks countries with an increase due to immigration, red marks countries with negative net migration. © Matti Kummu / Aalto University

Migration is a politically controversial and much-discussed topic in Germany and many other countries. However, precise data on the patterns of global immigration and emigration have so far been missing. A new study has now created a high-resolution global dataset for the period from 2000 to 2019 that captures annual net migration not only between different countries, but also at regional and global levels. This allows conclusions to be drawn about the causes of migration. Accordingly, climate-related droughts have so far played a smaller role than socio-economic factors. However, other climatic factors such as floods have not yet been recorded.

People all over the world are leaving their homes and moving to other regions or countries. The reasons for this are diverse: Some are fleeing wars and oppression, for some, climate change is making their region of origin increasingly uninhabitable, and some are hoping for better economic conditions further afield. For the target countries of this migration, immigration can bring advantages, including higher productivity through more workers. However, it also poses challenges for the social infrastructure and social system. So far, immigration and emigration have been recorded primarily at the state level. However, in order to analyze migration movements in detail, data at regional and global levels would be required.

Migration at the regional level

“There was a real need for such a dataset, but it didn’t exist,” says Venla Niva of Aalto University in Finland. “So we decided to create it ourselves.” Her team combined the birth and death rates with the general population development for over 2,000 administrative districts in 216 countries worldwide and thus calculated the share of migration. The researchers summarized their data in an interactive map that shows the annual net migration for each region for the period between 2000 and 2019, i.e. the result of immigration and emigration.

Initial analyzes of the data showed complex patterns. For example, the common assumption that people from rural areas move to cities is only partially true. “There is a widespread belief that urban areas attract people from rural areas, but that has not been the case everywhere. There are many places in Europe, for example, where the opposite is the case,” says Niva’s colleague Matti Kummu. “Migration from cities to rural areas has also been observed in parts of Indonesia, Congo, Venezuela and Pakistan, and when analyzed at the community level the picture becomes even more complex.” Overall, according to the analysis, a third of the world's population lives in Provinces in which rural areas have more immigration than emigration.

Socioeconomic factors as an indicator

In search of the causes of regional and global migration, Niva and her team combined their data set with other information. They used the United Nations Human Development Index (HDI) to draw conclusions about socioeconomic factors. This includes, among other things, gross national income, life expectancy and the average length of school attendance and thus provides an overview of a country's prosperity. In order to record climate-related causes of migration, the researchers chose the global drought index, which records precipitation, evaporation and dryness worldwide.

“When you look at the different factors together, the analysis shows that socioeconomic factors have played a larger role in net migration to date than climate,” says Niva. Areas with a high human development index experience more immigration than emigration, regardless of their drought. This applies, for example, to regions on the Arabian Peninsula, North America, Australia and the northern Mediterranean. However, the analysis left out other possible climate-related changes - including environmental disasters such as tsunamis and hurricanes as well as short-term or permanent flooding of areas. The current evaluation also did not take into account the capacity of the respective regions to adapt to climate change.

The poorest cannot emigrate

At the same time, it was found that emigration rates in regions with a very low human development index were lower than in regions in the middle of the scale. “It is not the poorest of the poor who are fleeing environmental disasters or environmental changes. Migration is an adaptation method used by people who are able to move,” says Niva. “Overall, migration is more complex than is generally assumed. Our findings contribute to the discussion about where and how migration occurs – it is not a Eurocentric phenomenon, as most migration occurs in other parts of the world.”

The researchers have published their data set freely accessible on the Internet and have already made it available to other research teams. “Our data offer several opportunities for future research on human migration within and between administrative borders – for example, in relation to extreme weather, disasters and conflict,” the team writes. “Capturing migration patterns not only between countries but also within countries is crucial for policy making, international cooperation and shared responsibility.”

Source: Venla Niva (Aalto University, Espoo, Finland) et al., Nature Human Behavior, doi: 10.1038/s41562-023-01689-4

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