Here we wrote that dust from Bodélé depression blows across the Atlantic to help fertilise the rainforests of the Amazon. The Bodélé depression was once an enormous lake called Mega Lake Chad in what is now the Sahara desert.
To analyse Mega Chad’s decline, researchers from Royal Holloway, Birkbeck and Kings College, University of London used satellite images to map abandoned shore lines. They also analysed lake sediment to calculate the age of these shore lines, producing a lake level history spanning the last 15,000 years.
Mega Lake Chad was once the biggest freshwater lake on earth covering 360,000 square kilometers of Central Africa and rapidly shrunk to a its present size just 1,000 years ago.
All that remains now is Lake Chad, which at 355 square kilometers is still quite large, but is just a fraction of its former glory. The lake, which crosses the borders of Chad, Niger, Nigeria and Cameroon, has been further reduced in size by humanity siphoning off fresh water from it.
 Armitage et al: West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad in Proceedings of the National Academy of Sciences – 2015