conditions during this time period. 1640 The first major historically recorded drought in the Sahel occurred around 1640. Based on the reports of European travellers, a major drought after generally wet conditions also took place during the 1680s. 1740s and 1750s Cycles of several wet decades followed by a drought were to be repeated during the 18th century. Sahelian drought again killed hundreds of thousands of people in the 1740s and 1750s. The 1740s and 1750s was recorded in chronicles of what is today Northern Nigeria, Niger and Mali as the "Great Famine", the worst for at least 200 years prior. It caused massive dislocation of the Sahelian states of the time, but also disrupted the Trans Saharan trade routes to North Africa and Europe. 1830s Around 1790 dry conditions similar to those of the late 20th century set in and continued until around 1870. After that, a very wet period set in for around 25 years, followed by a return to drier conditions. While the drying begun around 1895 and caused its first large famine only in the early 20th century, the 1820s and 1830s saw a 12 to 15-year drought and regional instances of major famine from Senegal to Chad. Historical records suggest this drought caused a large-scale emigration from the Bornu Empire, contributing to its rapid decline in the 19th century. In what is now northern Senegal, the Imamate of Futa Toro was struck by a famine caused by the failure of 1833's rainy season, leading to waves of famine until 1837. Early 20th century droughts The first rain gauges in the Sahel date from 1898 and they reveal that a major drought in the 1910s, accompanied by large-scale famine, was followed by wet conditions during the 1920s and 1930s, reaching a peak with the very wet year of 1936. The 1940s saw several minor droughts — notably in 1949 — but the 1950s were consistently wet, and expansion of agriculture to feed growing populations characterised this decade. Many have thought this contributed to the severity of the subsequent Sahel droughts. Late 20th century droughts Burkina Faso, northern Nigeria, southern Niger, far northern Cameroon (near Lake Chad) and central Chad all struggled with dwindling rain fall from the 1960s. On May 12 and 26, both Mauritania, the Sénégal River Area and neighbouring parts of both Senegal and Mali faced both a drought and famine. A literature review