Cassava's diffusion in Africa can be considered a fortuitous success story that highlights the flexibility and adaptability of African farming systems. Whilst the introduction of the crop at numerous points along the coast by the Portuguese formed the starting point, its acceptance, which governed the rate of diffusion, depended on cassava's particular characteristics, on ecological conditions, socio-cultural factors and regional political economies. Riverine trade and mass migration were probably the most important diffusion mechanisms, prior to the 20th century. Its diffusion was very uneven in space.

Prior to European intervention, cassava was adopted voluntarily by Africans for its particular characteristics, which are:

Adoption was also dependent upon factors related to postharvest processing and marketing, that is:

Our understanding of many of the details of the introduction of cassava in Africa remains limited. Intriguing questions relate to the emergence of the numerous cassava varieties that are found in farmers' fields today and to the way the crop was gradually incorporated into existing farming systems. With respect to the latter, we have no information on cultivation practices such as planting densities and intercropping (it is most likely that most cassava was intercropped).

Some of the evidence for Central and West Africa suggests that the crop may have been destined for the urban market at a very early stage. This could modify the classical image, held in many quarters, of cassava as a traditional food staple of Africa, and even the assertion that cassava is a 'female crop'. Unfortunately, it is not possible to relate the spread of cassava to changes in population density or to historic changes in gender roles across the continent.

The increased spread of cassava during and after the colonial period has been accompanied by profound social, economic and political changes. As a result, and because of the crop's tolerance of stresses and flexible management and harvest characteristics, cassava is now intimately bound up in the complex human and environmental systems of tropical Africa.

Table 1 summarizes trends in population growth, production, area and yield in the main cassava-producing countries. The source for these data are the FAO production yearbooks, and it should be noted that the most recent data are not always consistent with local census statistics. The FAO data are the best source of information we have on trends in cassava for Africa as a whole.

In the light of current rates of population growth, the situation is far from static. In the period between 1963 and 1986, cassava production in sub-Saharan Africa increased by an estimated 77%, as compared with a 96% population increase, while cassava area grew by 36%. In other words, yield and area increase have kept more or less the same pace, but there has been a slight relative decline in cassava production relative to population increase.

Overall trends mask marked regional differences, both between and within countries.