Version classiqueVersion mobile

Rural societies in the face of climatic and environmental changes in West Africa

Benjamin Sultan
Richard Lalou
Mouftaou Amadou Sanni
et al.

Part II. Impacts of the climate and environmental changes


Laurent Kergoat

Texte intégral

1The first part of this book sheds new light on climate variability in West Africa and more particularly in the Sahel. ‘The most severe multidecadal drought of the planet’ is always the one remembered best, and for very good reasons. This observation still h olds. However, we know that the precipitations of the past decade display a decreasing deficit although this is not the case every year. There are still drought years although they are not as dominant as in 1970-1980. A change in the regime of strongest rainfall is now taking shape. This is accompanied by a spectacular increase in the temperature at 2 metres during the hottest periods of the year—just before and after the rainy season.

2This climate variability over relatively long periods has very marked consequences. Indeed, most agricultural production involving both crop and livestock depends on precipitation. In addition, as the populations in practically all Sahelian regions are closely dependent on water resources such as surface water, ponds, reservoirs, rivers and groundwater, the impact that a multidecadal drought has had and still has today can be imagined.

3Although imagination and intuition can feed perception and common sense, they are not enough to draw up a precise review of the situation and identify the mechanisms that create the Sahelian environment. An illustration of this is desertification. This is a fundamental concept of the evolution of arid and semi-arid zones that is the subject of an international convention. In recent years, the desertification of the Sahel has generated debate with very different theories, opposing rapid desertification to overall re-greening. The theories are generally supported by very inadequate observations that are sometimes minor and sometimes subjective. ‘Re-greening’ is a concept derived from the satellite observations available since the 1980s and its interpretation is not immediately clear: is the satellite signal related to Sahel vegetation? To tree density? What causes re-greening? Important answers to these questions are provided in Chapter 6.

4Likewise, the recent evolution of water resources in the Sahel is the subject of contradictory theories with a contrast between shortage and increase. Hydrological observations since the 1970s have shown an increase in Sahelian river discharges in Burkina Faso, an increase in the water feeding seasonal ponds in western Niger and infiltration to groundwater. Does the phenomenon cover the whole of the Sahel? Is it caused by changes in land use? Might the situation be reversible during the coming decades? Answers to these questions are provided in Chapters 7 and 9.

5Even if climate forecasts are still uncertain (see Chapter 3), reasonable hypotheses can be put forward giving plausible ‘ranges’ for the decades to come when the mechanisms involved have been identified. The physical environment is the point of departure but is not the only feature in these questions of vulnerability. An important link in the assessment of vulnerability in the Sahel is the relation between crop or livestock farming systems and the environment. Chapter 8 contains a detailed comparative study of two ‘terroirs’—one pastoral and the other agropastoral—in which the authors examine the viability of livestock farming in both situations, presenting a set of data and analyses that are rare for this region. Chapter 10 contains a full study of the sensitivity of crop yields to climatic variations. The authors use climate scenarios and show that the most important factors for the Sahel are not necessarily those that might come to mind in a context of rainfed crops. Combined with preceding studies of the changes in temperature in the first part of the book, the results raise questions about agriculture that it is important to address rapidly.

6An extremely up-to-date picture of what we know about these questions is shown in the second part of the book. The results and conclusions often differ from what might be imagined outside a circle of experts—and sometimes within such circles. At a time when fact checking and decoding are reaching the media, we hope that this book will be an occasion for broad sharing of knowledge and conclusions. Given the media focus on these questions, their political and social importance and their incorporation in sometimes ideological statements, the responses are critical. I’ll just say here, so as not to anticipate the conclusions of the authors of subsequent chapters, that it is essential to possess rigorous, long-term observations of environmental resources. What these chapters show is that observations—and field observations in particular—on which expertise is based are the main driving force for gaining environmental knowledge in West Africa and elsewhere. They make it possible to drawn up balances, put forward hypotheses and build theories and scenarios.

© IRD Éditions, 2017

Conditions d’utilisation :

Rechercher dans OpenEdition Search

Vous allez être redirigé vers OpenEdition Search