The document discusses the Sahel region of Africa. It defines the Sahel as the transitional zone between the Sahara Desert to the north and subtropical savannas to the south. Countries in the Sahel like Mauritania, Mali, Niger, Chad, Sudan and Burkina Faso have experienced desertification as the Sahara Desert creeps southward due to overgrazing and drought. Nomadic groups like the Tuareg people have historically crossed the northern deserts with livestock herds. The document also discusses how Sudan was divided into two countries, Sudan and South Sudan, after a referendum in 2011.