The Effect of Cumulative and Combined Environmental Shocks on Migration

• In Event: The Impacts of Extreme Weather

Abstract

Climate change is expected to increase the frequency and intensity of climate events such as storms, floods, droughts, and sea level rise (IPCC 2021). In turn, these climate events may increase migration flows especially for vulnerable people. While the existing literature examines the occurrence/impact of a single climate event on people’s migration decisions, people experience the occurrence of a repeated climate event or the combination of sudden- and slow-onset events over a certain period of time. The impact of a succession of a specific climate event or the combination of climate events on migration can be very different from the impact of a single event, irrespective of its intensity. However, due to a lack of appropriate data, i.e., panel data, no studies exist that quantify the specific impact of repeated or combination of climate events on population movements. We hypothesize that recuring gradual events, i.e., sea level rise and riverbank erosion which permanently erode fertile agricultural land and destroy houses and infrastructure to increase permanent migration. Recurring sudden events, i.e., floods, on the other hand, because of their temporary nature and in riverine contexts tend to replenish soil and nutrients to floodplains, making them ideal sites for agriculture are likely to lead to temporary migration. We empirically evaluate the abovementioned expectations with newly collected individual-level panel data: approximately 1800 randomly selected household heads residing in 36 villages along the 250 kilometers of the Jamuna River in Bangladesh an area heavily affected by floods and riverbank erosion were repetitively interviewed (14 survey rounds) in the period June 2021 to January/February 2024. In selecting the locations of the surveys, we employ a quasi-experimental design to compare affected and unaffected populations at a similar baseline risk in experiencing the two different types of environmental/climate events in order to isolate the causal effect of recurring and combined environmental events on respondents’ migration behavior. Preliminary findings suggest that affectedness by erosion significantly increases the likelihood of migration. This effect gets even stronger for households which have been affected in two consecutive years. Flooding has a significant effect only if it leads to severe impacts or if it coincides with erosion affectedness. These findings have significant policy implications by underlining that repeated affectedness by environmental shocks might significantly increase out-migration from vulnerable regions.

Author

• Vally Koubi, ETH Zurich