As recently as 5,000 years ago, the Sahara — today a vast desert in northern Africa, spanning more than 3.5 million square miles — was a verdant landscape, with sprawling vegetation and numerous lakes. Ancient cave paintings in the region depict hippos in watering holes, and roving herds of elephants and giraffes — a vibrant contrast with today’s barren, inhospitable terrain.
The Sahara’s “green” era, known as the African Humid Period, likely lasted from 11,000 to 5,000 years ago, and is thought to have ended abruptly, with the region drying back into desert within a span of one to two centuries.
Now researchers at MIT, Columbia University and elsewhere have found that this abrupt climate change occurred nearly simultaneously across North Africa. The team traced the region’s wet and dry periods over the past 30,000 years by analyzing sediment samples off the coast of Africa. Such sediments are composed, in part, of dust blown from the continent over thousands of years: The more dust that accumulated in a given period, the drier the continent may have been.