Desertification has occurred worldwide. The biophysical and socio-economic complexity of this phenomenon has challenged our ability to categorize, inventory, monitor and repair the condition of degraded lands. One of the most important distinctions to be made in relation to land degradation is between cultivated land used for annual crop production and `rangelands'. Grazing by free-roaming livestock is the traditional primary use of the world's rangelands. However, there is growing recognition of the importance of these vast acreages for wildlife habitat, hydrology and ground water recharge, recreation and aesthetics. This text focuses on the desertification of rangelands and explores processes, problems and solutions. Chapters in the first section evaluate interactions between `natural' and human-induced disturbance regimes, thresholds, and non-linear change with respect to vegetation, hydrology, nutrients and erosion. Chapters in the second section examine socio-economic constraints and approaches for preventing and reversing degradation. The book provides a contemporary, process-oriented perspective on rangeland degradation of value to students, policy-makers and professionals alike.