Soils

Topsoil is a fragile and elusive interface between the biosphere and the lithosphere. The soils (i.e. the pedosphere) have been deeply affected, and even (in some cases) created, by human action. No analysis of vegetation, land cover, and land use can be undertaken without a comprehensive knowledge of the soils, their nutrient status, and their stability.

Because of the great variety and variability of soil development, in both time and space, a sharp distinction between natural and anthropogenic changes is quite difficult to make. Human-induced changes are mainly caused by agricultural land use (crops and livestock), and by transportation and settlements. Roads and settlements have decreased the total area of productive soils (especially fertile top soils) in all urbanized societies. This process is of great concern now in Asia, where most of the population still live on farms but migration to cities is accelerating.

In a number of studies of the relation of agricultural production and the population carrying capacity, the importance of soil constraints within the biophysical framework has been stressed. Several soil zones have been identified where present food demand exceeds the agricultural production potential. These are designated as critical zones of food insecurity.

Climatic and soil data have also increasingly been used to assess vulnerability. This has been done on a global scale by emphasizing biophysical driving forces. It has also been done at the local and regional scale by associating vulnerability with changes in crop yields, harvest failures, and agro-ecological potential. In this connection the ecotoxic impacts of industrial wastes and agricultural chemical usage on the biosphere have not been treated adequately.