The Sahara in North Africa is the largest hot desert on the planet, spanning an area of around 3.6 million sq miles (9.2 million sq km). Over time, the desert has slowly pushed itself southward, covering more and more of the African continent and desertifying large swathes of land.
In response, African nations have undertaken one of the most ambitious environmental and humanitarian initiatives in human history: the Great Green Wall. The goal is simple: to plant as many trees as possible across the African continent, all to stop the encroaching desert.
The initiative has grown in scale since its inception in the 1970s, but it still has a long way to go. Click through this gallery to see how the African continent has fought to keep itself green.