The three major agro-ecological zones are the Sahelian, the Sudanese and the Coastal zones where production and consumption can be easily classified. (1) In the Sahelian zone, millet is the principal cereal cultivated and consumed particularly in rural areas and increasingly, when accessible, in urban areas. Exceptions include Cape Verde where maize and rice are most important, Mauritania where sorghum and maize are staples, and Senegal with rice. The principal substitutes in the Sahel are sorghum, rice, and cassava flour (Gari), the latter two in times of shortage. (2) In the Sudanese zone (southern Chad, central Nigeria, Benin, Ghana, Togo, Côte d'Ivoire, southern Burkina Faso, Mali, Senegal, Guinea Bissau, Serra Leone, Liberia) maize and sorghum constitute the principal cereals consumed by the majority of the population. They are followed by rice and tubers, particularly cassava and yam. (3) In the Coastal zone, with two rainy seasons, yam and maize constitute the most important food products. They are supplemented by cowpea, which is a significant source of protein.
The three trade basins are known as the West, Central, and East basins. In addition to the north to south movement of particular commodities, certain cereals flow horizontally. (1) The West basin refers to Mauritania, Senegal, western Mali,
Sierra Leone, Guinea, Liberia, and The Gambia where rice is most heavily traded. (2) The Central basin consists of Côte d'Ivoire, central and eastern Mali, Burkina Faso, Ghana, and Togo where maize is commonly traded. (3) The East basin refers to Niger, Nigeria, Chad, and Benin where millet is traded most frequently. These three trade basins are shown on the map above.