The Sahel is a region located to the south of the Sahara Desert stretching from the Atlantic Ocean in Mauritania to the shores of the Red Sea in Sudan and Eritrea. It covers Mauritania, Burkina-Faso, Mali, Niger and Chad, an area of three million square kilometres. It is a transitional biome between the arid Sahara and greener savannahs further south. Due to its harsh weather and desertification since the second half of the twentieth century, the region has become increasingly uninhabitable and has been characterised by famines, droughts, and social conflict.