ABSTRACT
A wide variety of processes damage land and soil, which can have natural or human causes or a combination of the two. These processes include water and wind erosion, physical, chemical, and biological degradation, salinization, alkalization, and air and noise pollution. Each has three aspects: state, rate, and risk. The state is the extent to which the land has already been degraded and is, for instance, visible in lands which are gullied, deflated, or salinized. The rate is the speed at which degradation is now occurring and can be measured in terms of annual change. Water and wind erosion can, for instance, be assessed in terms of weight of soil lost, salinization by the rise in soil electroconductivity and pollution by the increase in toxic substances per unit area. The risk is the rate of lowering of present or potential land productivity, measured in economic terms, caused by activities currently in progress such as the replacement of vegetation by bare fallow. Methods have been developed in order to quantify, grade, and map each of these aspects (e.g. Riquier, 1978; Morgan, 1979). Noise pollution is an increasing problem. Although it depresses property prices (Walters, 1975), its effect on land values still awaits detailed investigation.
