General Introduction

1 The Spatial Framework, the Concepts of Aridity and Drought: the Soils and the Vegetation

1.1 Attempts at Global Localization of Drylands

1.1.1 The Cold Polar Deserts

1.1.2 The Warm Tropical Deserts

1.1.3 The Coastal Deserts

1.1.4 The Lee-side Deserts

1.1.5 The Continental Deserts: The Turan Desert as an Example

1.1.6 Semi-Deserts or Semi-Arid Zones, a Wide Zone of Transition

1.2 The Concepts of Aridity and Drought in Drylands

1.2.1 Definition of Degrees of Aridity

1.2.2 The Land Surface Affected by Aridity on the African Continent

1.2.3 The Different Types of Drought

1.2.4 Postglacial Aridification and Advance of the Deserts in Africa?

1.2.5 The Droughts of the 20th Century in North-Equatorial Africa

1.2.6 Study of the Drought of 1984-1985 in Kenya and Its Consequences

1.2.7 What Lessons Do We Learn from the Last Drought in the Sahel?

1.3 The Thin Vulnerable Soils of Low Agricultural Potential

1.3.1 The Dryland Soils of North-Equatorial Africa

1.3.2 The Soils of Turan

1.3.3 The Specific Characteristics of Dryland Soils

1.4 Vegetation Covers: Economic Potentials and Droughts

1.4.1 Heterogeneity of the Vegetaion Cover in Drylands

1.4.2 Adaptability of Plants to Aridity and Drought

1.4.3 The Vegetation Along the Dryland Diagonal Sahara-China

1.4.4 The Open Vegetation Cover of the Sahel

1.4.5 The Vocation of Grazing the Sahel Steppe

1.4.6 Potential Foraging Value and Carrying Capacity

1.4.7 Weakening of the Vegetation Cover by Human Activities: Different Estimates

1.4.8 Behaviour of the Vegetal Cover During the Drought of 1969-1973

1.5 Conclusions

2 Resources vs. Hydrological and Aeolian Constraints

2.1 Inventory of Resources

2.2 Hydrological Constraints in Drylands

2.2.1 Specific Hydrological Features

2.2.2 The Fugacity of the Surface Waters

2.2.3 The Allochthonous Water-Courses

2.2.4 Rill Wash and Runoff in Tropical Drylands

2.2.5 Ponds and Water Bodies: The Third Type of Water Reserve in Drylands

2.2.6 The Underground Waters

2.2.7 Degradation of Soils by Water Erosion

2.3 The Omnipresent Wind in Dry Ecosystems

2.3.1 Wind -- Definition and Basic Principles of Its Dynamics

2.3.2 The Effects of Wind on Vegetation and Soil Humidity

2.3.3 Aeolian Processes in Sand and Loess Drylands

2.3.4 Aeolian Deposits

2.3.5 A Proposal for the Classification of Dunes

2.3.6 The Theory of the Global Aeolian Action System (GAAS)

2.4 Conclusions

3 Human Genius: The Search for Water and Its Management -- Battle Against the Wind

3.1 Non-Irrigated Agricultural Systems in Drylands: Their Difficulties in the 20th Century

3.1.1 Itinerant Rain-Fed Agriculture and Fallow Periods

3.1.2 The Move Towards Irrigated Agriculture

3.1.3 Livestock Breeding, Nomadism, Pastoralism, and Transhumance

3.1.4 Demise and Mutation of Nomadism

3.2 The Geohistory of Water Management: The Hydraulic Civilizations

3.2.1 Aridity, Drought and the Birth of Modern Man

3.2.2 Aridity, Drought and the Birth of Agriculture

3.2.3 Aridity, Drought and the Birth of Hydraulic Societies

3.2.4 The Great Hydraulic Systems of the Drylands

3.3 Traditional and Modern Hydraulic Techniques

3.3.1 Modern Search for Water, Luxury Projects

3.3.2 Parsimonious Management of Surface Waters

3.4 Traditional and Modern Irrigation

3.4.1 Traditional Irrigation

3.4.2 Modern Irrigation

3.4.3 Reservoir Dams

3.5 A Response to the Aeolian Constraints -- The Art of Counteracting the Effects and Damage Done by Wind

3.5.1 Basic Principles for Fixing Mobile Sands and Dunes

3.5.2 Control of Barchans and Linear or Parabolic Dunes

3.5.3 Strategies for the Control of Aeolian Erosion on the Level of the Various Units of the Global Aeolian Action System (GAAS)

3.6 Conclusions

4 From Ingenuity to Decadence: Geohistory of an Actual Decline -- Grounds for Hope?

4.1 Proposals for a Definition of Decadence

4.2 Ten Principles Explaining Decadence

4.2.1 The Naturalist Perspective

4.2.2 The Neo-Malthusian Perspective

4.2.3 The Marxist Perspective

4.2.4 The Anti-Colonialist and Neo-Colonialist Perspective

4.2.5 The Judicial and Socio-Cultural Perspective

4.2.6 The Global Perspective

4.2.7 The Perspective of Non-Adapted Strategies and Technologies

4.2.8 The Perspective of Underdevelopment as the Cause for the Degradation of the Environment

4.2.9 The Moral Perspective

4.2.10 The Perspective of Worldwide Ignorance

4.3 The Oases-Mutation, Decline or Resurgence?

4.3.1 Description of the Oasis Space: Definition of the Term

4.3.2 Chronological Framework of Oases According to Their Agrotechniques

4.3.3 The Oases of the 20th Century: Decadence of a Strategy of Development

4.4 Soil Degradation, Irrigation, Salinization and Decadence

4.4.1 The Degradation of Dryland Soils by Salinization

4.4.2 Irrigation and Decadence: Four Case Studies

4.5 Desertification -- An Expression of Decadence?

4.5.1 Difficulties with the Sense of the Word Desertification

4.5.2 What Is Really Happening?

4.6 A Glimmer of Hope

General Conclusion

References

Geographic Index

Subject Index