WASHINGTON, DC — In 80 percent of African countries, people have moved to rivers and cities during droughts, increasing the number of people living in flood-prone areas in recent decades, according to a new study. This resettlement pattern will likely intensify in the coming decades as climate change is expected to make droughts more frequent and severe.
“It’s an aggravating cycle of how many people are adversely affected by drought, and not just in the ways we’d normally expect,” said Serena Ceola, a hydrologist at the University of Bologna in Italy who led the study. “As regional climates change and both droughts and floods become bigger problems, more people will struggle to find a safe place to settle. People may be moving from one drought-affected place to another, or moving somewhere that simply carries different climate risks.”
In Somalia, for example, more than 3.8 million people have been displaced in part because of drought over the past three years. Many of these climate refugees sought shelter near riverswhere farming could resume, but heavy rains and flash floods subsequently displaced more than half a million people.
The study was published in The Future of Earth, which publishes interdisciplinary research on the past, present and future of our planet and its inhabitants. Prior to this study, research on drought-induced migrations in Africa focused on individual countries or specific drought events, limiting scientists’ understanding of how drought affects large-scale human settlement patterns. The new study is the first to examine changes in human settlement patterns associated with droughts on a continental scale.
“We want the whole society to know how many people are moving from one climate threat to another,” Ceola said.
FREAKING DRY
Drought may push people closer to rivers to continue agricultural activities, and others may adapt by moving to cities, which offer a variety of economic opportunities when drought curtails agriculture. Scientists have hypothesized that drought may be the primary driver of human displacement, but many factors—often inextricably linked to drought itself—can contribute to displacement. Drought can exacerbate conflict, political violence, and food and job insecurity, each of which can trigger mass migration in its own right.
The researchers chose to focus only on drought because of its potential impact on many different factors. They used two indices, EM-DAT and SPEI-12, which respectively reflect socioeconomic and evapotranspiration impacts of drought, to look for droughts in 50 African countries from 1992 to 2013. They included the years before and after the drought in their analyses. to test for the strength of the drought signal and the lingering effects of drought on human movement.
To determine whether people moved to the rivers, the researchers used satellite detection of nighttime light to check for either changes in the brightness of existing settlements or the development of new settlements. They used annual World Bank census data by country to track populations in urban centers.
WHERE DOES THE DROUGHT LEAD PEOPLE?
The study found that people moved towards rivers or urban centers in up to 80% of African countries experiencing droughts, as indicated by at least one of the two indicators used. During drought years identified by at least one of the
Based on the indicators, in about half to three-quarters of all countries studied, settlements are moving closer to rivers, and one-third to one-half of the countries were experiencing urban population growth. The signal of urban growth could have been weaker than river-based migration because people can move to cities for many reasons, Ceola said.
Seventeen countries experienced droughts according to both drought indices during the study period. Up to 65% of these countries saw increased human movement towards rivers during drought years when the year before the drought was included in the analysis.
Specifically, all southern African countries saw drought-related migration to rivers based on at least one drought indicator during the study period. Ceola singled out Burundi, Guinea-Bissau and Namibia as particularly interesting.
The methods have some limitations. Night lights are used as a proxy for human settlements and activities, which means that the amount of light observed may not reflect the number of people. Smaller concentrations of lights may not show up and may leave out poorer groups that don’t have enough light to show up. Limited data for many regions and populations on the continent means scientists must be creative with available information sources to prepare people and governments for current and future risks, Ceola said.
“Policymakers need data and detailed information to implement strategic planning, support sustainable development and increase the resilience of people living in vulnerable areas. Likewise, people living in these areas should be aware of the dangers and should have the opportunity to move freely to safer locations,” said Ceola.
NOTES
his study is published in The Future of Earthan open access journal. View and download a pdf of the study here.
EPISODE TITLE:
“Drought and Human Mobility in Africa”
AUTHORS:
- S. Ceola (corresponding author), Department of Civil, Chemical, Environmental and Materials Engineering, Alma Mater Studiorum Universita di Bologna, Bologna, Italy
- J. Mård and G. Di Baldassarre, Center for Natural Hazards and Disaster Science, Uppsala, Sweden, and Department of Earth, Air, Water and Landscape Science, Uppsala University, Uppsala, Sweden
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Contributed by Shannon Banks