The study of cattle pastoralism in general and pastoral labour in particular has concentrated on the arid and semi-arid zones, largely because the majority of cattle are located there. The absence of pastoral groups in humid and sub-humid environments is related to both the high arable populations in these regions and the incidence of trypanosomiases.
In Nigeria, however, an unusual situation prevails; the arid zones and the coastal forest are heavily populated, but the Middle Belt, or Sub- humid Zone (SHZ), has been sparsely inhabited certainly since 1900. Such a clear pattern is not found elsewhere in West-Central Africa and it has generally been argued that the situation in Nigeria is a consequence of the extensive raiding from the Northern Emirates in the eighteenth and nineteenth centuries. However, arable farmers have not avoided the Middle Belt for ecological reasons, and the Middle Belt has a potential for supporting a much larger population.