Peak dry period: forest retreat and desert dune advance in Nigeria

Approximately coincident with the last maximum of the last glaciation in northern Europe, beginning around 20,000 BC, West Africa was much drier than at present. Lake Chad was dry and sand dunes formed over its floor and in parts of northern Nigeria, especially east of Kano, indicating a mean annual rainfall at the time of less than 150 mm where there is now more than 850 mm. The forest disappeared except in relict coastal areas.