Development of the desert locust outbreak in Mauritania, case of 2003/2004

Mauritania is known as a permanent habitat of the desert locust Schistocerca gregaria (FORSK. 1775). Between 1993 and 2004, two outbreaks and one upsurge occurred. The outbreak that started in 2003 exceeded all historical accounts. Rather than depending on swarms from the Central Region, it developed from concentrations of indigenous populations, leading to an upsurge, and later, to an outbreak. This unexpected development was triggered by abundant rainfall in the summer in Sahelian countries, particularly Niger, Mali, and Mauritania after years of drought. Rains contributed to locust breeding and concentrations, changing locust behaviour from solitary to gregarious. A combination of an unusually heavy rainfall in October 2003 in central and northern Mauritania with continuing drought in the south contributed to locust gregarization. This rapid development of locust upsurge in Mauritania was caused by ecological conditions, particularly vegetation and soil moisture. In northern Mali, 80% of vegetation had dried out by the end of October, and the soil was dry. At the same time, this type of vegetation was lush and green in central Mauritania and soil was wet. This complementarity between the two habitats led to a rapid increase of locust populations in central Mauritania in November and December 2003 due to influx of groups from Mali. As a result, the first large swarm was observed in December 2003. Successful locust breading continued in Mauritania in January and March 2004, and at least three generations were produced between August 2003 and March 2004, contributing to a build-up of an outbreak. (Texte intégral