Dryland degradation (in other words, desertification) is defined for the purposes of this paper as a persistent decrease in the capacity of an arid or semiarid ecosystem to supply a range of services, including (but not restricted to) forage, fuel, timber, crops, fresh water, wild-harvested foods, biodiversity habitat and tourism opportunities. A conceptual model is proposed that allows syndromes to be evaluated. The hypothesis is that the majority of instances of desertification in southern Africa are due to one or more of a relatively small set of distinct biophysical mechanisms, interacting with a similarly small set of human system contexts. The paper describes 13 biophysical mechanisms, focusing on the system dynamics that lead to the loss of ecosystem services, and why the loss is persistent. It suggests the diagnostic symptoms and the conditions under which the syndrome occurs, and the remedial actions that can be taken. A preliminary attempt is made to estimate the aerial extent and severity of the various syndromes. It is suggested that application of these ideas will help to make the evaluation of dryland degradation more rigorous, and pave the way to better-prioritised and focused interventions.
Keywords: Desertification, ecosystem services, natural capital
African Journal of Range & Forage Science 2009, 26(3): 113–125