Spatiotemporal Characteristics of Drought Events in Africa's Great Green Wall Region During 1950–2022

Abstract

Understanding historical spatiotemporal drought patterns is crucial for effective drought adaptation and mitigation strategies. Despite the launch of Africa's Great Green Wall (AGGW) initiative by the African Union to combat desertification in the semi-arid Sahel region, there remains a limited comprehensive long-term spatiotemporal assessment of drought patterns. In this study, we analyzed the drought spatiotemporal characteristics in the AGGW region using the Standardized Precipitation-Evapotranspiration Index (SPEI) at multiple timescales (1-month, 3-month, 6-month, 9-month, and 12-month) from 1950 to 2022. Despite regional variations, the results showed an overall increasing drought trend across the AGGW during the past 73 years. Trends of drought change per year were −0.012, −0.015, −0.018, −0.009, and −0.021 for SPEI01, SPEI03, SPEI06, SPEI09, and SPEI12, respectively. Significant spatial variability in drought duration, frequency, intensity, and trend were observed, mainly larger values concentrated in the northern and central areas of AGGW. Two significant turning points were detected, occurring in 1973 and 1996 that indicated the periods of 1950–1972 and 1973–1995 non-significant drought increase while significant severe drought occurred in the late periods (1996–2022), with widespread spatial coverage. Seasonal drought variation demonstrates an increasing trend in autumn, spring, summer, and winter across all SPEI time scales, with notably larger rates during autumn and winter. Finally, these findings provide important insights into the characteristics and mechanisms of droughts across the AGGW region and have a significant implication for drought adaptation and mitigation strategies to meet the core objectives of the AGGW regional initiative.