ABSTRACT
It would be impossible to reduce the variety of specific situations described earlier to several simple factors. Thus, the purpose of this chapter is simply to emphasise the role played by the most prominent among them. Nevertheless, we will certainly fall short of giving, in a satisfactory manner, an account of all the local situations which can be encountered in the Sahelian zone. At least we will attempt to introduce a little comprehension to what has remained, until now, a simple statement of diversity.
