Humans affect the Sahara Desert by causing global climate change, which in turn causes the Sahara to spread. As of 2015, the Sahara expands southward by 30 miles every year.
Global climate change due to human activities and pollution causes the expansion southward of the Sahara Desert into the Sahel. The Sahel is a region just south of the Sahara desert that extends from the east to the west coast of Africa. Not only is this region already environmentally degraded but the people living in it are poor. As the Sahara reaches into the region, desertification of the Sahel occurs, damaging the semi-arid ecosystem and destroying Africa's farmland.
In order to stop the encroachment of the Sahara, experts have suggested the construction of a Green Wall or a wall of trees that stretches across the southern border of the Sahara from Senegal in the west to Djibouti on the east. Experts believe that a wall of tree not only operate as a windbreak to hold back the desert sands, but the roots also help to prevent soil erosion. The plan specifies the introduction of native trees to the Green Wall that are more likely to survive in the arid environment. Some of the countries plan to dig rainwater reservoirs along the wall for future use.