Lake Chad – Chad, Niger, Nigeria, Cameroon Once one of Africa’s largest bodies of fresh water, Lake Chad is now a ghost of its former self. According to a study by University of Wisconsin-Madison researchers, the lake is now one 20th of the size it was 35 years ago. Massive irrigation projects, an increasingly dry climate, and declining rainfall have all contributed to its decline. This montage shows the lake in 1963, 1973, 1987 and 1997. The red colour represents vegetation on the lake bed where there used to be water.

Photograph: NASA/AFP