This video of Lake Chad, at the southern edge of the Sahara, reveals a rapid decline in water supply. Once one of Africa’s largest lakes, Lake Chad has shrunk by around 90 percent since the 1960s. The receding water is due to a reduction of precipitation induced by climate change, as well as the development of modern irrigation systems for agriculture and the increasing human demand for fresh water. Straddling the borders of Chad, Niger, Cameroon, and Nigeria, the lake is a major source of fresh water for millions of people in the area. It is also a source of fish, and it was once rich in biodiversity. November 6, 1984–October 31, 2018.