Introduction

In its broadest sense ‘land degradation can result from any causative factor or combination of factors, which damage the physical, chemical or biological status of the land and which may also restrict the land's productive capacity. In the agricultural sense, for example, soil erosion reduces the land's ability to sustain yields or stock numbers, and thus may reduce economic returns. A large number of factors may contribute to land degradation. The Food and Agriculture Organisation (FAO), for example, lists erosion, salts and alkali, organic wastes, pesticides, radioactivity, heavy metals, fertilisers and detergents as all being potentially causative agents of degradation (Rauschkolb 1971). In an Australian context, the causes and responses to land degradation have been comprehensively reviewed by Woods (1983). He lists a number of environmental problems including loss of sustainable production because of degradation, declining water quality, loss of genetic diversity, land use conflict etc, as all being major issues worthy of further study.

Land degradation, however, is by no means limited to specific geographic zones, nor does it occur at a uniform rate. Degradation can be insidious: for example, when perhaps a few millimetres of topsoil are blown off cultivated fields every year; or castastrophic: severe erosion associated with the washing out of the Daintree road in northern Queensland during the 1985 monsoon season. Furthermore, its effects are often not simply limited to the locality where damage is noted. Many effects may be off site – for example, when transported soil particles are deposited in a water storage.