However scanty it may be, the dryland vegetation constitutes a fundamental resource that transforms solar energy into food and which protects and stabilises the surface of the ground. This vegetation survives by adapting to water deficit in ways which are important as they determine seasonal differences in the usefulness of dryland pastures. Any equilibrium is readily disturbed. Where meagre vegetation is further reduced to expose the ground surface, humus will be mineralized and soil structure lost.

Rain will fall directly on the soil, and break it down, and the sun will bake a thin crust which prevents additional water from sinking in.

The denuded soil is essentially infertile, with poor structure and water relations.

All these changes constitute a shift towards a more hostile environment for plants, with the result that the vegetation responds less well to rain and produces less biomass, and many plants tend to die off at an increasingly early stage of drought.

The United Nations recognises the seriousness of the issue and has established a Convention to Combat Desertification.