Abstract
Migration manifests an important response and adaptation measure to changes in the environment and socioeconomic conditions. In a time when environmental stressors and risks are unprecedentedly increasing, understanding the interplay between the underlying factors driving migration is of high importance. While the relationships between environmental and socioeconomic drivers have been identified conceptually, the comprehensive global-scale spatial quantification of their interactions is in its infancy. Here, we performed a geospatial analysis of gridded global net migration from 1990 to 2000 using a novel machine learning approach which analyses the interplay between a set of societal and environmental factors simultaneously at the place of origins (areas of net-negative migration) and destinations (areas of net-positive migration). We diagnosed the importance of eight environmental and societal factors in explaining migration for each country, globally. Nearly half of global in- and out-migration took place in the areas characterized by low adaptive capacity and high environmental stress. Regardless of the income level, income was the key factor in explaining net-migration in half of the countries. Slow-onset environmental factors, drought and water risk, were found to be the dominant environmental variables globally. Our study highlights that factors representing human capacity need to be incorporated into the quantitative diagnosis of environmental migration more rigorously.
Highlights
Recent events such as migrant caravans from Central America to the United States in 2019, the Venezuelan migrant and refugee crisis in 2019-20 and the 2015 crisis of large refugee flows from the Middle East and North Africa to Europe have been frequently linked with preceding severe drought episodes in the country of origin (Chemnick 2019, Gustin and Henninger 2019, Markham 2019, Podesta 2019)
Our analysis shows that in 1990-2000, the majority of net-negative and net-positive migration occurred in areas characterized by high environmental stress (ES)
We found that the majority of global net-positive migration was characterized by high environmental stress and medium level of adaptive capacity (Figure 4c)
Summary
Recent events such as migrant caravans from Central America to the United States in 2019, the Venezuelan migrant and refugee crisis in 2019-20 and the 2015 crisis of large refugee flows from the Middle East and North Africa to Europe have been frequently linked with preceding severe drought episodes in the country of origin (Chemnick 2019, Gustin and Henninger 2019, Markham 2019, Podesta 2019). A stereotypical view that environmental change would induce mass-migration fluxes towards the “Global North” has been repeated in both research and policy-making for decades (Boas et al 2019). Investigating the fundamental, manifold role of environmental stress as a trigger and driver of migration has substantially gained both scholarly and public attention. Do various environmental factors influence migration in different directions and magnitudes Gray and Mueller 2012, Cattaneo and Peri 2016, Kubik and Maurel 2016), other societal factors and their interactions play an important role. The understanding of human migration needs to account for complex interactions between different drivers of migration at the micro, meso and macro levels (Boas et al 2019, Abel et al 2019, Borderon et al 2019, Hoffmann et al2021)
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