Defining the Sahel. B-ordering an area study

The chapter presents the aims and methods used to define the limits of the study area of this volume, the Sahel. First, a critical approach is applied to both the concept of 'area studies' and the meaning of the term 'Sahel' itself, in order to illuminate its colonial genealogy. Multiple definitions, climatic-botanical and political, have been attributed to the Sahel over time, by different authors and in diverse contexts. Its delimitation on maps has been openly questioned and contested. While aware of the problematic implications in any delimitation choice, it is nevertheless necessary, in order to deal with satellite remote sensing and other geo-localised data, to draw the boundaries of the study area. We proceeded by identifying rainfall thresholds deemed significant, outside and inside the area, following their movement in the dry and wetter phases. The challenge is to construct a cartography capable of rendering the areal definition of the Sahel visible and fluid at the same time. In the same vein, the political boundaries that divide the Sahel have been analysed not as an absolute datum but by relating them to multiple variables. It is a question of rethinking the very foundation of cartography such as the common tools of cartographic representation, for example the concept of 'isohyet' as average data to identify climatic areas or 'boundaries' as a sharp line to define political jurisdictions.