Lake Chad spans 4 national borders in the central Sahel: Niger, Nigeria, Chad, and Cameroon. Since the 1960s it’s shrunk to about 5% its ancestral size, due to overuse, mismanagement, and climate shifts.

This NASA photo uses SRTM data combined with Landsat 8 to highlight the edges of the basin that was once the size of the Caspian Sea:

About 7,000 years ago, a vast lake spread hundreds of square kilometers across north-central Africa. Known to scientists as Lake Mega Chad, it...