1.3 How much soil is there and where is it?

Only about 7.5% of the Earth’s surface provides the agricultural soil on which we depend for the world’s food supply (Table 1.1), and this fragment competes, sometimes unsuccessfully, with all other needs: housing, cities, schools, hospitals, shopping centres, land fills, etc.

Table 1.1. How much soil is there? Broad estimates of the coverage of the Earth’s surface by different features

Surface feature

Percentage coverage

Aquatic: oceans, seas, rivers and lakes


Deserts: polar and mountain regions unsuitable for agriculture


Rocky and other poor-quality terrestrial regions unsuitable for agriculture


Terrestrial regions suitable for agriculture


Indeed, there may not be enough soil in the first place. A subsistence diet requires about 180 kg of grain per person per year, and this can be produced on 0.045 hectares of land. In contrast, an affluent high-meat diet requires at least four times more grain (and four times more land, 0.18 hectares) because the animals are fed on grain and conversion of grain to meat is very inefficient.

The Earth has about 0.25 hectares of farmland per person, but only about 0.12 hectares per person of farmland is suitable for producing grain crops. As it stands, the Earth does not have enough land for all inhabitants to enjoy an affluent diet as that is presently defined (see Table 1-2 in Miller & Gardiner, 2004, and see Fig. 11.12 for a potential alternative).

This chapter describes the key physical and chemical features of the soil habitat that govern the biodiversity and activity of soil organisms.

Updated July, 2019