The Sahara

A tree grows in the Sahara. (Reuters/Rafael Marchante). As recently as 5,000 years ago, one of the world’s driest and most uninhabitable places, the Western Sahara desert, was home to a vast river system that would rank as the world’s 12th largest drainage basin if it existed today. French researchers have identified an ancient river system that they believe formed during humid spells that overtook the desert over the past 245,000 years, according to a study published this week in the journal, Nature Communications.

Using an advanced imaging system on the Japanese Advanced Land Observing Satellite, Charlotte Skonieczny, from the L’Institut Français de Recherche pour l’Exploitation de la Mer, and her team, found sediment layers typical of river-borne material that outlined a river stretching about 500km (320 miles) long. Researchers said that with this river system, the Sahara would have once been the “location of extensive vegetation, animal life and human settlements.”

Theories that the Sahara was once home to waterways that sustained life from rhinos to humans and various species of fish have gained traction in the last few years. In 2013, researchers argued that, based on computer modeling of the Sahara as it existed 100,000 years ago, monsoon rains would have been heavy enough to feed three main rivers. Some paleohydrologists believe these waterways are the key to the answer of how humans migrated out of central Africa.

“People sometimes can’t get their head around climate change and how quickly it happens. Here’s an example where within just a couple of thousand years, the Sahara went from being wet and humid, with lots of sediment being transported into the canyon, to something that’s arid and dry,” Russell Wynn, a scientist with the National Oceanography Centre in Southampton who was part of a team that mapped a massive underwater canyon in the Sahara in 2003, told the Guardian.

The Sahara could be home to life and vegetation again. The researchers estimate that the river system held water nine times over the past 200,000 years with periods of humidity and climate change occurring every 20,000 years.