in a meta-analysis of recent scientific literature on the drivers of migration into 11 coastal megacities located in delta regions in Asia and Africa. The study finds that migration to these cities, which include Bangkok, Dhaka, Guangzhou, and Karachi, has primarily resulted from a combination of economic, demographic, political, and social factors rather than environmental conditions. Yet the study also notes the difficulty of separating out these other factors from environmental conditions such as land degradation, land scarcity, or extreme events (Seto, 2011).

In exploring the environmental drivers of migration in more detail, Black et al. (2011b) suggest that environmental change may directly contribute to migration through mechanisms that contribute to changes in the reliability or availability of ecosystem services such as productivity of land; food, energy, and water security; and exposure to hazards. Environmental change may indirectly contribute to migration through its effects on economic drivers, such as livelihood opportunities, or on political drivers, such as conflicts associated with availability and access to resources. Connections between environmental change and migration can be seen in the case of Niger, where Afifi (2011) found that environmental degradation, including the interrelated problems of drought, deforestation, and soil degradation, led to reduced incomes among farmers, herders, and fisherman, thereby contributing to economic migration. Afifi’s study (2011), which was based on fieldwork conducted during 2008 in two regions of the country (Niamey and Tillabéri), found that migrants were typically young men who left their families behind in search of work either in another region or in another country. Most of the approximately 60 migrants interviewed in the study identified economic factors such as poverty and unemployment as key reasons for migrating, but almost all (90 percent of those interviewed) indicated that environmental problems also played a role in their decision to migrate (Afifi, 2011).

Recent literature further emphasizes that individual or household migration decisions are generally dependent not only upon social, economic, political, and demographic drivers, but also on the particular characteristics of individuals and households, including level of wealth, education, worldviews, ethnicity, and so forth. Individual migration decisions are also influenced by what Black et al. (2011b) term “intervening obstacles or facilitators,” such as an individual’s social network, legal and political mechanisms, the presence of recruitment agencies, and so forth (see Figure 5-2). As such, the same set of “structural” drivers may contribute to different outcomes for different households depending both on a household’s characteristics and on intervening barriers and facilitators to migration.

While caution is needed when generalizing from past findings to a future climate where extreme climate events will be more likely and more severe, we can postulate that disruptive migration may potentially result

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