4. Desertification: A Tale of Two Feedbacks

R.D. GRAETZ
CSIRO, Division of Wildlife and Ecology, PO Box 84, Lyneham, ACT 2602, Australia

4.1 Introduction   4.1.1 Desertification: a man-made phenomenon   4.1.2 Desertification as a disturbance   4.1.3 Desertification as an experiment: limitations of the evidence   4.1.4 Strategy of analysis 4.2 Nature of ecological theory   4.2.1 Desertification as a theoretical problem?   4.2.2 Contemporary understanding of arid ecosystems   4.2.3 Utility of ecological theory 4.3 Nature of arid ecosystems   4.3.1 The ecological essence of aridity   4.3.2 System description   4.3.3 Primary productivity   4.3.4 Nutrient flows   4.3.5 Secondary (herbivore) productivity   4.3.6 System-level interactions and feedbacks 4.4 The Sahel of Africa: a case study   4.4.1 The setting and the system 4.4.2 Man in the system 4.4.3 The catalytic disturbance 4.4.4 The phenomenon of desertification 4.5 A systems analysis of desertification 4.5.1 Components and interactions 4.5.2 Society and pastoral man   4.5.3 Man and herbivores 4.5.4 Herbivores and vegetation   4.5.5 Vegetation and soils 4.5.6 Climate and soils 4.6 Summary and conclusions References