1.2 Soil, the essential terrestrial habitat
The conventional estimate is that 75% of the Earth is covered with water; oceans, lakes, rivers, streams. However, less than 1% of the known species of fungi have been found in marine habitats (see pp. 346-351 in Carlile, Watkinson & Gooday, 2001). Fresh water is inhabited by many water moulds (an informal grouping that includes the most ancient fungi and fungus-like organisms, which will be discussed in more detail in Chapter 3), but the overwhelming majority of fungi occur in association with soil; where ‘in association with’ means in or on the soil, or in or on some live or dead plant or animal that is in or on the soil.
As Wikipedia points out ‘Soil is also known as earth: it is the substance from which our planet takes its name’ (http://en.wikipedia.org/wiki/Soil). Soil is, therefore, the essential terrestrial habitat. In saying this we do not underestimate the importance of other categories of habitat. But they are categories: grassland, forest, coastal, desert, tundra and even cities and suburbs, and ultimately all these habitats depend on their soil. Without soil, no grass, so no grassland habitat. Without soil, no trees, so no forest habitat. Few, if any, organisms can be found on bare rock, wind-blown sand or ice. Fundamentally, terrestrial life on Earth depends upon the earth, and to show how fungi contribute to the formation of soil, this is where we choose to start our story.
Updated December 16, 2016