Drought in the Sahel

Abstract

The Sahel region of West Africa is well known as a region of environmental degradation. The reported incidence of desertification has been challenged but persistent and widespread drought is still widely accepted. Drought, defined solely as a function of rainfall, is believed to have commenced in the early 1970s and continued through to the present. It is usually defined as a meteorological phenomenon and standardised rainfall anomalies are employed to indicate the severity of negative departures from the ‘norm’. There are several difficulties with this approach. The period of standardising rainfall has changed from 1931–1960 to 1961–1990 but the impacts on drought occurrence have not been fully determined. The spatial aggregation of rainfall anomalies may mask important local variation and the purely statistical approach to defining drought takes little account of human impact. The first two issues, averaging period and spatial aggregation, are investigated through an analysis of rainfalls in Continental Sahel (Bukina Faso, Mali and Niger). A new classification of drought classes is suggested. Despite the clear evidence of negative rainfall anomalies for rainfalls aggregated across the Sahel region, it is found that the averaging period has a significant impact on our perceptions of the occurrence of what can be considered to be meteorological drought according to the definition employed and that there is significant spatial variation.