Around 6,000 years ago the Sahara Desert looked dramatically different. A vast body of water known as Mega Chad covered roughly 360,000 square kilometres in what is now southern Sahara larger than all five North American Great Lakes combined.
The ancient lake existed during Africa’s Humid Period, when much of North Africa was significantly wetter and greener than today. Changes in Earth’s orbit increased summer sunlight over the northern tropics, strengthening the African monsoon and bringing rainfall deep into the Sahara.
As orbital conditions changed, rainfall weakened and the giant lake gradually shrank. Researchers have reconstructed its former size using ancient shorelines and lake sediments, with estimates of its peak area ranging from about 360,000 to more than 400,000 square kilometres.
Today only a small remnant survives as Lake Chad, shared by Chad, Niger, Nigeria and Cameroon. Its open water area is just a tiny fraction of the ancient lake maximum extent.
The modern decline of Lake Chad is also a major concern. Its surface area fell dramatically during the second half of the 20th century, while drought, changing rainfall patterns and growing demand for water particularly for irrigation continue to put pressure on the basin.
The Lake Chad basin supports nearly 40 million people, many of whom depend on farming, livestock and fishing. The story of Mega Chad therefore offers more than a glimpse into the Sahara past it highlights how changes in water availability can reshape ecosystems and human livelihoods.