The southern fringes of the Sahara are dynamic. As rainfall varies, land patches on the edge chop and change between green and arid brown. Human activities, like overgrazing, deforestation or poor irrigation, further degrade some of the already arid parts of the Sahel, resulting in desertification. As the planet heats up, changes in rainfall patterns can cause longer dry spells on the southern boundaries of the Sahara, stretching the desert further down, and affecting nearly a million people and their livelihoods in the Sahel.

In 2007, the African Union responded to the aridification of the Sahel by resolving to build a “Green Wall” running 8,000 kilometers (5,000 miles). The tree barrier, as it was initially conceptualized, would extend all the way from Dakar in the west to Djibouti in the east and be completed by 2030. The idea of the wall slowly morphed into a more flexible concept with a socioeconomic angle: a mosaic of forested land, interspersed with farmland and grassland, spread over 780 million hectares (1.93 billion acres), that also benefits local communities.