The southern area of the country presents forests and cultivated areas, the central area is mainly savannah, while the northern part is semi-desert, is the so-called Sahel, the antechamber of the desert itself. The main rivers of the country are Mouhoun (Black Volta), the Nakambé (White Volta) and the Nazinon (Red Volta). To the east flows shorter rivers belonging to the Niger river basin, including the Béli, Gorouol, Goudébo and Dargol. Burkina Faso is one of the poorest countries of the world, the main problem is the severe drought, leading to the territory rapid desertification. Agriculture remains the main economic sector of the country, it is practiced primarily in the southern and western areas, there are grown sorghum, millet, maize, batata, cassava, potatoes, sugar cane, cotton, tomatoes, sesame, tobacco, karité, peanuts and rice. Important is nomadic breeding there are bred mainly cattle, sheep and goats. Forests, intensely exploited, provide a quantity of timber increasingly small. Interesting are the mineral resources there are deposits of manganese, gold, uranium, vanadium, diamonds, zinc, bauxite, lead, nickel and phosphates.