Migrant networks and adaptation

Migration is an important means to cope with the impacts of climate-related shocks. Research shows that networks of prior migrants aid this crucial adaptation mechanism.

Increasing concentrations of atmospheric greenhouse gases have already committed us to environmental stresses that are bound to increase¹. Moving within a country or to another country offers an important opportunity for adaptation. Historical examples abound in which people respond to extreme weather conditions through migration. For example, a multi-century drought is likely to have contributed to the de-urbanization of the Indus Valley of Pakistan and Northern India some 4,000 years ago². Similarly, hundreds of thousands of families in the 1930s left US and Canadian prairies to move west to Oregon and California because of the period of drought and dust storms known as the Dust Bowl³. A number of studies have explored the link between climatic shocks and migration, largely concluding that climatic shocks and hazards can lead to both internal and international migration, in particular if the country of origin is a developing one⁴. A recent paper from Mahajan and Yang⁵ analyses the effect of hurricanes on international migration to the United States, finding that hurricanes are responsible for a substantial increase in migration rates from 159 origin countries.

Credit: Imaginima/E+/Getty/ NASA

Globally, tropical cyclones are responsible for large losses in terms of lives and money. Because of global warming, the intensity of these phenomena is projected to increase, with higher peak wind speeds and an increase in heavy precipitation¹. Thus, increased migration activity in the future is possible or indeed likely.

Still, the human response to extreme weather events, such as hurricanes, is often ambiguous. From a theoretical point of view, there is a trade-off between the incentives to move as a consequence of an extreme event and the resources needed to do so. Home-location shocks on the one hand raise the returns of migration by lowering the attractiveness of remaining at home, but, on the other, raise the fixed cost of migration. Hurricanes can destroy assets, making it more difficult for credit-constrained households to finance relocation, but migrant networks may support mobility. A large literature has identified that migrants’ networks aid further migration of people⁶, for example by mitigating the hazards of crossing the border⁷ or assisting newcomers in finding a job at their destination⁸. Following the occurrence of a weather shock, large migration networks can reduce the monetary and psychological costs of relocating to the United States, making migration more likely. However, previous migrants may provide financial assistance through remittances that then reduce the incentives to move.

Thus, one question that Mahajan and Yang explore, in an effort to better understand whether hurricanes that occurred between 1980 and 2004 around the world encouraged or inhibited international migration to the United States, is whether the networks of earlier migrants from the same country of origin amplify or attenuate the effect of hurricanes on international migration. To do so, they use the stock of compatriots already in the United States in 1980 as a proportion of the origin country’s population in the same year as a proxy indicator for the strength of the existing migrant network. They find that, overall, hurricanes are responsible for a substantial increase in the migration rates from 159 origin countries to the United States, and larger networks of compatriots in the United States magnify this relationship. An increase of one standard deviation in their hurricane index, which is a function of a hurricane-force wind speed, boosts annual emigration rate to the United States by 11.8%. If they allow the effect of the hurricanes to vary depending on the size of the prior network, they find that for size lower than 0.86% (as a ratio between the migrant stock abroad and the origin country population), hurricanes reduce migration, whereas for size greater than 0.86%, they increase emigration. For a country with a migrant network of 6%, which corresponds to the 90th percentile of the prior migrant stock distribution, a one standard deviation increase in the hurricane index increases migration by 18%. Although Mahajan and Yang conclude that the network amplifies the positive migration response to hurricanes, another reading of the result is that the ability to use migration as an ex-post strategy to cope with the impacts of a weather shock relies heavily on the presence of a large established network.

They also find that established migrants at the destination aid emigration by formally sponsoring relatives at home for legal, permanent migration. The presence of a large network of compatriots allows hurricane-induced flows of migrants to enter through legal channels and eventually stay permanently at the destination.

These results shed new light on the potential for migration to act as an adaptive mechanism. Although previous research has found that extreme climatic events are a possible driving force of migration, this result suggests that adaptation is enhanced when there is a large diaspora to aid mobility. The finding that an existing migrant network potentially increases the chance of leaving a community after an extreme weather event is important because it gives some indication of where vulnerable populations might become locked into their geography, and where they might not. Rather than unquestionably leading to environmental migrants, certain populations may become trapped in vulnerable locations as a consequence of climate shocks.

This result is consistent with emigration functioning as an ‘escape valve’. International migration has been found to moderate the negative effect of warming on civil conflict in countries of origin⁹. Moreover, impediments to sustainable development can be reduced by through migration opportunities. Recent research looking at residents displaced when Hurricane Katrina hit New Orleans (USA) shows that African American women experienced greater attainment opportunities at their destinations¹⁰.

It is of paramount importance that research in this field improves our understanding of how and when climatic shocks lead to increased migration, given that the effects can be heterogeneous with respect to a multitude of factors. The migration response to climatic change is moderated by social, economic and political factors, implying that climate effects are contingent upon context and the livelihoods of affected populations.