ABSTRACT
Most, though not all, authorities agree that desertifi cation occurs in drylands, which can be defi ned using the boundaries of climatic classifi cations (Figure 5.1) and make up nearly half of the world’s land surface. Arid, semi-arid and dry subhumid zones can be taken together as comprising those drylands susceptible to desertifi cation, excluding hyper-arid areas because they off er so few resources to human populations that they are seldom used and can hardly become more desertlike. Recent thinking on desertifi cation refers to it as a process of land degradation in drylands. e concept of degradation is linked to using land resources – which include soil, vegetation and local water resources – in a sustainable way. Land that is being used in an unsustainable manner is being degraded, which implies a reduction of resource potential caused by one or a series of
Figure 5.1 The world’s drylands (after UNEP, 1992a).
