A new study has shown that the rainy season’s onset date can be a reliable early indicator of seasonal drought conditions in sub-Saharan African regions that have most often needed emergency food assistance in the last decade.
The PLOS ONE journal published the study on January 20, 2021. It is titled, “A slow raining season onset is a reliable harbinger of drought in most food insecure regions in Sub-Saharan Africa”. Seven researchers working at the University of California, United States, worked on the report.
Their study evaluated the relationship of the onset dates and peak Normalised Difference Vegetation Index (NDVI) stratified by acute food insecurity (AFI) risks. They used the United States Agency of International Development (USAID)-funded Famine Early Warning Systems Network (FEWS NET). In short, the study assessed the relationship between onset dates of rains and droughts in East Africa, West Africa, and Southern Africa.
The results show the onset date can effectively explain much of the interannual variability in peak NDVI in the regions with the highest AFI risk level, particularly in East Africa. Several parts of the SSA, mostly the East African regions, have reported the “Crisis” phase of AFI—requiring emergency food assistance—at least one-third of the time between April 2011 to present.
In 2019, more than 45 million people struggled with finding enough food across 14 African countries, The New Humanitarian reported. The study also noted that SSA countries have been experiencing increased AFI since 2015, with more than 100 million Africans estimated to have received emergency food assistance last year.
According to the report, an onset date delay of at least one dekad (10 days) increases the likelihood of seasonal drought conditions. In regions with the highest AFI risks, an onset delay of just one dekad doubled the chance of the standardised anomaly of peak NDVI being below -1. In those regions, a 2-dekad delay in the onset date is associated with a very high probability (50%) of seasonal drought conditions (-1 standardised anomaly of NDVI).
“Since agricultural droughts often contribute to or worsen food insecurity, an early indication of agricultural drought should help policymakers make decisions to mitigate the most adverse impacts of food insecurity and save lives and livelihoods”, says Shraddhanand Shukla, the study’s lead author told SciDev.Net.
The other six researchers that worked on the report are Greg Husak, William Turner, Frank Davenport, Chris Funk, Laura Harrison, and Natasha Krell. Except for Natasha, all the researchers work with the Climate Hazards Center, Department of Geography, University of California.
Shukla adds that agencies such as the Food and Agriculture Organisation of the United Nations that provide early warning on food insecurity have been monitoring rainy season onset as an indicator of droughts. She said this motivated his team to explore the accuracy of the method in the SSA.
The researchers used satellite images of vegetation cover as measures of drought conditions in the SSA and quarterly reports on food insecurity risks between April 2011 and February 2020, to assess how the conditions are linked to the rainy season’s onset date.
The Climate Hazards Center is working on operational tools to provide agricultural drought forecasts based on predictions and observations of the rainy season onset, Shukla says.
Patricia Nying’uro, a climate scientist at the Kenya Meteorological Department, told SciDev.Net that the study provides useful information as a starting point for drought response planning in the SSA, but added that farmers must be better prepared for the research to be helpful.