Drought and Human Mobility in Africa

Human mobility from droughts is multifaceted and depends on environmental, political, social, demographic and economic factors. Although droughts cannot be considered as the single trigger, they significantly influence people's decision to move. Yet, the ways in which droughts influence patterns of human settlements have remained poorly understood. Here we explore the relationships between drought occurrences and changes in the spatial distribution of human settlements across 50 African countries for the period 1992-2013. For each country, we extract annual drought occurrences from two indicators, the international disaster database EM-DAT and the standardized precipitation evapotranspiration index (SPEI-12) records, and we evaluate human settlement patterns by considering urban population data and human distance to rivers, as derived from nighttime lights. We then compute human displacements as variations in human distribution between adjacent years, which are then associated with drought (or non-drought) years. Our results show that drought occurrences across Africa are often associated with (other things being equal) human mobility toward rivers or cities. In particular, we found that human settlements tend to get closer to water bodies or urban areas during drought conditions, as compared to non-drought periods, in 70%-81% of African countries. We interpret this tendency as a physical manifestation of drought adaptation, and discuss how this may result into increasing flood risk or overcrowding urban areas. As such, our results shed light on the interplay between human mobility and climate change, bolstering the analysis on the spatiotemporal dynamics of drought risks in a warming world. Prolonged water shortages induced by droughts can have severe consequences on both the environment and society. For instance, the mobility of people can be influenced by drought events. In order to test this assumption, we relate the movement of people to drought occurrences, without considering any additional factor. We focus on Africa, since it is one of the most drought-prone continents and the movement of people is more prominent compared to other areas. We find that people tend to move closer to rivers and to urban centers during droughts, as compared to non-drought periods. This pattern is found for the majority of African countries, which suggests a large-scale signal. The increased movement of people toward rivers during droughts might generate larger human losses if flood events take place in the future. A new methodology integrating satellite data is developed for evaluating drought-induced human displacements in AfricaWe found that 70%-81% of African countries exhibit larger displacements during droughts, as compared to non-drought periodsHuman displacement toward rivers and urban centers is triggered, other things being equal, by drought occurrences

Automated summary

Droughts influence human settlement patterns, causing people to move closer to water bodies or urban areas. This tendency may increase flood risk and lead to overcrowding in cities.