General Conclusion

Abstract

Definition and geographical positioning of the drylands, of aridity, drought, soils and vegetation were the object of the first part of this book. The second part was dedicated to water, its scarcity and its erosive force and lead to the statement that this basic resource is constraint number 1, the wind being constraint number 2. We furthermore described the high degree of sensibility of the drylands, which are unstable and are exposed to greater ecological risks than most other climatic zones, and at the same time possess a lower agricultural potential. They appear more demanding than the temperate and perhaps also the tropical humid environments, and in the context of sustainable development they are more vulnerable. However, paradoxical as it might appear, the drylands are attractive and because of this they exhibit high population densities. The equilibrium between these low potentials and the population growth remains difficult to preserve. A series of a few dry years will suffice to break the equilibrium between the survival of the society, the exploitation of the natural resources and the conservation of the environment.