Climate change, natural disasters, and migration Updated

The mitigating role of migration

Population movement is a natural way to deal with climatic shocks, particularly when livelihoods are destroyed. Migration can be considered as an adaptation strategy when disasters occur because it helps mitigate the adverse effects of the shocks by providing new opportunities and resources to affected people. It also serves as a coping strategy when other solutions have failed. For instance, in the case of drought, potential solutions, which in some cases may be survival strategies, can include changing consumption patterns by reducing the number of daily meals, selling household assets, using food reserves, and benefiting from solidarity through gifts, loans, and aid. Having many possible coping strategies will reduce the likelihood of migration due to shocks.

In 2020, developing countries (including low-, and middle-income countries, based on World Bank’s classification ) accounted for 91.1% of global internal displacement due to disasters. Most of the displacements are from middle-income countries (Figure 1). Moreover at a country level, this corroborates the fact that people at the extremities of the income distribution do not necessarily migrate in the aftermath of disasters. Indeed, the poorest cannot afford to migrate and the richest have other mitigation strategies, such as the possibility to recover their lost assets or better access to effective infrastructure and social services, which allow them to cope with disasters without migrating. Therefore, people at the middle of the income distribution are those who do not have many alternatives at their disposal to deal with natural disasters and, at the same time, can afford migration costs.

However, it is important to point out that the rather low rates of disaster-related migration from poor and high-income countries do not necessarily mean that the poorest and the richest people in a specific country do not migrate. There is some heterogeneity within developing countries, which shows that the level of vulnerability of an individual as well as the intensity and severity of the shock also matter when it comes to the relationship between disasters and migration. Vulnerability is correlated with factors such as exposure to shocks, poverty level, social structure, assets and income diversification, and the political situation. For instance, people living in a politically unstable environment have fewer survival strategies available to them than those living in a peaceful one. The intensity refers to the violence of the disaster-related shocks. The severity of the shock is measured through the frequency, temporal spacing, and spatial distribution of the event, and the way people affected perceive the shock. The frequency of shocks represents the number of events in a given period. The temporal spacing measures the elapsed time between two events. The spatial distribution characterizes the extent of the shock in a given region; for instance, an event that is isolated to a specific area is easier to deal with than an event affecting an entire country. Finally, the way people perceive shocks is shaped by expectations and experiences from previous events.

The role of vulnerability and severity is highlighted in the case of Bangladesh over the period 1994–2010. Moderate flooding, as compared to less severe flooding, increased an individual's likelihood to move locally, but decreased her likelihood to make a long-distance migration; this was especially true for vulnerable groups such as the poor or women. Moreover, households that were not directly affected by the flooding but lived in areas with severe crop failure were more likely to move [2]. Figure 2 provides a good illustration, for the case of Africa, that all types of natural disasters are not equivalent in terms of their effect on migration. Flood was the main source of disaster-related displacement between 2009 and 2018, with 18.1 million displaced people, accounting for 85% of total disaster-related displacement during the period.

The association between the extent of the migration response and the severity of the disaster is also observed in developed economies. Evidence shows, in the case of the US, that severe disasters increase net out-migration from a county, while migration response to milder disasters is smaller at the county level [3].

The role of remittances

Migration can serve as a coping mechanism through remittances sent back by emigrants to communities affected by climatic shocks and natural disasters. Remittances help increase the resilience of households to natural disasters and reduce their vulnerability to the effects of shocks. Migrants’ transfers provide insurance to the left-behind in case of shocks. Consequently, remittances help households deal with income shocks caused by disasters. Evidence shows that remittances have a stronger poverty reducing-effect in countries hit by natural disasters [4], confirming the insurance role of remittances against the economic costs of natural disasters. This highlights the importance of lowering the costs of sending remittances.

Internal vs international migration

Studies that look at the impact of climatic factors on internal migration use the urbanization rate, measured as a country’s share of urban to total population, as a proxy for rural-urban migration due to the unavailability of comparable internal migration data across countries and over time [5], [6]. This is based on the assumption that most internal population displacement is due to rural-urban migration. However, evidence on the link between climate change, natural disasters, and internal migration is rather mixed and varies depending on the nature of shocks and across regions. On the one hand, natural disaster is found to increase the urbanization rate in developing countries [6]. On the other hand, evidence shows that increasing temperatures over a long period of time positively affect internal migration in middle-income countries but not in low-income countries [5].

Evidence also shows that climatic shocks and natural disasters could lead to international migration [1], [7], [8]. For instance, natural disasters closely related to climate change such as storms, floods, wet mass movements, drought, wildfire, and extreme temperatures, have been shown to boost migration from developing countries to the six main OECD destination countries. Furthermore, this effect is primarily driven by migration of highly educated people [1]. Education is correlated with income, which may indicate that those highly educated people can afford migration costs. This suggests that climate change-related disasters may lead to brain drain from developing countries.

Migrant networks have also been found to be key to climatic shock-induced international migration as they facilitate immigration by reducing the fixed cost of migration. There is evidence that countries of origin with higher prior migrant stock in the US can benefit to a larger extent from formal sponsoring for legal, permanent immigration into the US [8].

Another body of evidence finds that climatic shocks such as weather anomalies affect international migration through their effect on internal migration, which is called an “economic geographic channel” [7]. For instance, in the case of sub-Saharan Africa, weather anomalies have been found to be positively associated with rural–urban migration because of their effects on the agricultural sector. This internal migration, in turn, leads to an increase in international migration by raising the number of workers in cities, translating into lower wages and increasing people’s willingness to move internationally in search of higher wages. Weather anomalies can also lead to high international migration through a so-called “amenity channel” by increasing the spread of disease and risk of death [7].

The role of liquidity constraints: Slow vs. rapid onsets and temporary vs. permanent migration

The positive relationship between climatic shocks and migration has been challenged in the economics literature. There is some evidence showing that climatic shocks do not necessarily lead to more internal or international migration if the affected people are burdened by liquidity constraints or if they have to deal with slow-onset events such as slowly changing temperatures [5] or droughts [9]. Conversely, it might be argued that when faced with rapid-onset events such as cyclones, storms, and floods, people could be forced to move because they lose everything all at once, which is not necessarily the case with slow-onset events [9].

Studies also show that due to liquidity constraints, victims of rapid-onset events are more likely to embark on short-distance migrations [6] or short-term relocations, rather than on permanent or long-distance migration [2]. Viewed through the lens of migration costs, liquidity constraints can be extended to more general socio-economic costs such as the existence of important migrant networks in possible destination places. In the case of international and permanent migration for example, migrant networks can facilitate new migration in the aftermath of a climatic shock by providing a less costly, legal route to immigration, through such provisions as family reunification immigration policies [8].