Desertification

1. What is Desertification?: Definitions and Evolution of the Concept.- 1.1 Definitions of Desertification.- 1.2 The Evolution of the Concept of Desertification.- 1.2.1 The Age of Awareness.- 1.2.2 The Age of Wrong Perception or Misconception.- 1.2.3 The Age of Doubt.- 1.2.4 The Myth of the Encroaching Desert.- 1.2.5 The Dawning of the New Realism.- 1.3 General Conclusion, Chapter 1.- 2. "Desertification" or Land Degradation: Location and Dimension in Time, Vulnerabilitiy of Soil and Plants in Drylands.- 2.1 Introduction.- 2.2 Location of "Desertification" or Land Degradation, Threatened Areas and Drought-Prone Regions.- 2.3 Dryness Ratio and Drought.- 2.3.1 Dryness Ratio.- 2.3.2 Drought.- 2.3.2.1 Meteorological Drought.- 2.3.2.2 Hydrological Drought.- 2.3.2.3 Agricultural Drought.- 2.4 The Droughts of the 20th Century Throughout the World.- 2.5 The Vulnerability of Soils in Drylands.- 2.6 The Survival of Plants in Dry or Seasonally Dry Ecozones.- 2.7 General Conclusion, Chapter 2.- 3. Dimensions in Space of "Desertification" or Land Degradation: The Degree and Specificity in Each Continent.- 3.1 Introduction: Global Dimension in Space of "Desertification".- 3.2 Sub-Saharan Africa: Traditional Extensive Agriculture, Unadapted High Technology, and Land Degradation.- 3.2.1 Droughts in the Sahel.- 3.2.1.1 Paleo-Droughts and Historical Droughts.- 3.2.1.2 20th Century Droughts.- 3.2.1.3 Drought and Shifting Isohyets in Eastern Mali. Where Are the Most Severe Effects of Drought?.- 3.2.2 The Bioclimatological Ecozones.- 3.2.3 Traditional Land Occupation. Potentialities and Agricultural Limits in High Climatic Risk Drylands.- 3.2.3.1 Hunting.- 3.2.3.2 Fishing.- 3.2.3.3 Domesticated Stock-Keeping.- 3.2.3.4 Agriculture in Sub-Saharan Drylands.- 3.2.4 What Are the Risks and How Can They Be Avoided?.- 3.2.4.1 In the Sahel.- 3.2.4.2 In the Sudanian Zone.- 3.2.4.3 The Sudano-Guinean Subzone.- 3.2.5 Environmental Difficulties of Development. Disasters: What Disasters?.- 3.2.5.1 Overgrazing.- 3.2.5.2 Overcropping and Deforestation.- 3.2.6 Conclusion.- 3.3 Egypt: An Example of the Misapplication of High Technology Leading to Man-Made "Desertification".- 3.3.1 Causes of Land Degradation.- 3.3.2 Processes of Land Degradation.- 3.3.2.1 Water Table Rising.- 3.3.2.2 Absence of Nile Alluvium Resulting in Wind Erosion.- 3.3.2.3 Loss of Nutrients.- 3.3.3 Effects of Land Degradation.- 3.3.4 Conclusion.- 3.4 China: A Sophisticated Traditional Intensive Agriculture Beginning to Be Modified by High Technological Methods and "Desertification" or Land Degradation.- 3.4.1 Introduction: The Agricultural Origin of Land and Degradation in China.- 3.4.2 Classification of the Desertified Areas in China.- 3.4.2.1 Deserted Land and Desertified Land in the Arid Ecosystems.- 3.4.2.2 A Second Type of Desertified or Degraded Land in China in Semi-Arid and Dry Subhumid Steppes.- 3.4.3 The Major Indicators of Degradation.- 3.4.3.1 Changes in Topography.- 3.4.3.2 Changes in Composition of the Vegetative Cover.- 3.4.3.3 Changes in Texture of the Top Soil.- 3.4.4 Human Factors Leading to Environmental Change in Semi-Arid and Dry Subhumid Zones in China.- 3.4.4.1 Overcultivation and Degradation.- 3.4.4.2 Overgrazing and Degradation.- 3.4.4.3 Firewood Collection and Degradation.- 3.4.4.4 Land Degradation by Misuse of Water Resources.- 3.4.4.5 Land Deterioration and Nonrural Human Activities.- 3.4.5 Conclusion.- 3.5 Transition from Traditional Low Technological to High Industrial Agriculture and Land Degradation in the Former USSR.- 3.5.1 Dry Ecozones in the Former USSR.- 3..5.2 Aridity and Other Physical Factors Leading to Land Degradation.- 3.5.2.1 The Climatic Factors.- 3.5.2.2 Soils.- 3.5.2.3 The Vegetation Resources.- 3.5.2.4 Water Resources.- 3.5.3 Human Activities and Land Degradation.- 3.5.3.1 Old Oases.- 3.5.3.2 Land Degradation in Desert Rangelands.- 3.5.3.3 Ecological Implication of Irrigation in Drylands.- 3.5.3.4 Environmental Impact of Industrial Development in Dryland of the Former USSR.- 3.5.4 Aeolian Action and Land Degradation in the Sandy Deserts of the Former USSR.- 3.5.5 Conclusion.- 3.6 High Technological Capital-Intensive Pastoralism and Land Degradation or "Desertification" in a Dry Continent: Australia.- 3.6.1 Human Causes of Land Degradation in Arid Australia.- 3.6.2 Grazing and Other Agricultural Activities in Semi-Arid Australia.- 3.6.3 Land Degradation in Irrigated Areas.- 3.6.4 Land Degradation in Nonagricultural Areas.- 3.6.4.1 Impact of Urban Settlements.- 3.6.4.2 Impact of Mining.- 3.6.5 Conclusion.- 3.7 High Technological Capital-Intensive Agriculture and Soil Degradation or "Desertification" in North America.- 3.7.1 Location of Land Degradation in the Drylands of the USA.- 3.7.2 The Causes of Land Degradation.- 3.7.2.1 Excessive Water Consumption: First Cause of Land Degradation.- 3.7.2.2 Overgrazing: Second Cause of Land Degradation.- 3.7.2.3 Salinization: Third Cause of Land Degradation.- 3.7.2.4 Physical Soil Erosion: Fourth Cause of Land Degradation.- 3.7.2.5 Combined Causes and Mechanisms of Land Degradation.- 3.7.3 Conclusion.- 3.8 General Conclusion, Chapter 3.- 4. Processes Leading to Soil Degradation and "Desertification".- 4.1 Introduction.- 4.2 Physicochemical Processes of Degradation.- 4.2.1 Potential Modifications and Decay of Soil Structure.- 4.2.2 Leaching.- 4.2.2.1 Aspects of Degradation by Leaching in the Upper Horizons of the Soil.- 4.2.2.2 Aspects of Degradation by Leaching in the Lower Horizons of the Soil.- 4.2.3 Waterlogging.- 4.2.4 Salinization and Alkalinization.- 4.2.4.1 Processes.- 4.2.4.2 Case Studies of Salinization: An Age-Old Irrigation Problem.- 4.2.5 Conclusion.- 4.3 Physical Processes of Land Degradation: Water Erosion.- 4.3.1 Soil Loss.- 4.3.2 Deteriorating Mechanisms of Water Action.- 4.3.3 Raindrop and Splash Effect.- 4.3.4 Runoff Action.- 4.3.5 Conclusion.- 4.4 Physical Processes of Land Degradation: Wind Erosion; Where Is the Danger?.- 4.4.1 What is Wind?.- 4.4.2 The Influence of Topography on Wind Conditions.- 4.4.3 The Wind Action Sytem.- 4.4.3.1 Source Area.- 4.4.3.2 Transport Area.- 4.4.3.3 Deposit Area and Dune Formation.- 4.4.4 The Effects of Wind on Vegetation.- 4.4.5 Aeolian Soil Erosion.- 4.5 General Conclusion, Chapter 4.- 5. Prevention and Remendies.- 5.1 Introduction.- 5.2 Possibilities for Overcoming Climatic Risks in Drylands.- 5.2.1 Cloud Seeding an Weather Modifications.- 5.2.2 Strengthening of Meteorological Services.- 5.3 Avoiding the Threat to Vegetation.- 5.3.1 Vulnerability of Dryland Vegetation.- 5.3.2 How to Obtain Biological Recovery.- 5.3.2.1 Natural Recovery.- 5.3.2.2 Artificial Recovery.- 5.3.3 Solutions to Avoid Grazing Effects.- 5.3.3.1 Carrying Capacity.- 5.3.3.2 Mobile Resources for Nomadic Pastoralism.- 5.3.3.3 Game Ranching Instead of Cattle.- 5.3.3.4 Fodder Harvesting.- 5.4 Some Solutions to Improve Drylands Agriculture.- 5.4.1 Drought-Adapted Plants.- 5.4.2 Introduction of Lesser-Known Plants.- 5.4.3 Reclaiming Salty Soils and Water.- 5.4.4 Plant Breeding.- 5.5 More Integrated Rural Activities for Agriculture Amelioration.- 5.5.1 Multicrop Agriculture.- 5.5.2 Natural Bushland Exploitation.- 5.5.3 Soil Degradation and Rehabilitation of an Agropastoral Land in Tanzania. Hopeful "De-Desertification": Case Study.- 5.5.3.1 Degradation.- 5.5.3.2 Results of the HADO Projekt "De-Desertification" in Tanzania.- 5.6 Water Conservation Measures.- 5.6.1 Introduction.- 5.6.2 Difficulties in Obtaining Water.- 5.6.2.1 High Technology Solutions: A Mitigated Success.- 5.6.2.2 Low Technology Irrigation Systems and Water Conservation Measures.- 5.6.2.3 The Basic Requirements of Irrigation.- 5.6.2.4 Deep Borewells.- 5.6.3 Water Harvesting.- 5.6.4 Desalinization Techniques in the Search for Freshwater.- 5.6.5 Conclusions.- 5.7 Maintaining Soil Quality.- 5.7.1 Introduction.- 5.7.2 Halting Water Erosion.- 5.7.2.1 Control of Sheet-Wash and Rillwash.- 5.7.2.2 Gully Reclamation.- 5.7.3 Control of Damaging Wind Effects.- 5.7.3.1 Methods for Preventing Progression of the Barchans.- 5.7.3.2 Control of Seif Dunes.- 5.7.3.3 Strategies for the Control and Prevention of Sand Encroachment.- 5.7.3.4 Windbreaks, Shelterbelts, and Wind Barriers.- 5.7.3.5 Additional Methods of Controlling the Wind.- 5.8 Training and Research.- 5.8.1 Training.- 5.8.1.1 What Is Not Working?.- 5.8.1.2 What Can Tradition Bring?.- 5.8.2 Research Results.- 5.9 General Conclusion, Chapter 5.- 5.9.1 The Specific Solutions for China.- 5.9.2 Africa Must Find its Own Specific Remedies.- 6. General Conclusion: The Need for a New Realism.- 7. New Developments in Desertification (September 1993).- 7.1 Natural Causes: Droughts Since the Beginning of the Century.- 7.2 Human Causes.- References.- Author Index.- Subject hidex.