Life in the Soil - Soil: Reflections on the Basis of our Existence - page 55

Life in the Soil

The worms mingle the whole intimately together,
like a gardener who prepares
fine soil for his choicest plants.

Charles Darwin

Abstract The greatest biodiversity is in the soil, and this chapter describes the
soil's inhabitants—everything from fungi and bacteria to single-celled organisms,
mites and other bugs. How are they connected in the foow-webs of the soil? Who
eats whom? Fungi and bacteria are important for the decomposition of the organic
material in the soil, yet they work in different ways, which affects the circulation of
nutrients. Tropical rainforests have a diversity of species above ground whereas in
northern latitudes the diversity is to be found under the surface. Certain creatures,
such as earthworms, affect the structure of the entire soil ecosystem and acceler-
ate the circulation of nutrients. But when European earthworms invade forests in
Minnesota, biodiversity suffers. Termites can eat wood thanks to symbiotic micro-
organisms in their digestive tract; as they gather material to feed their larvae, they
affect the soil's fertility and the distribution of plants on the savannah. In addition,
they have contributed to the cultural development of the Australian Aborigines.

Diversity of Species in the Soil

Soil teems with life. A single gram can contain several hundred metres of fun-
gal hyphae and more than ten billion bacteria, along with microscopic worms
like nematodes and unicellular organisms such as amoebae and protozoa. Larger
organisms including springtails, mites, beetles and millipedes are present, too, but
in much smaller numbers.
One might well wonder how many organisms a child ingests when it sticks
dirty fingers in its mouth when playing outside. Probably billions. But eating a few
crumbs of soil would not normally make a child ill as most microorganisms are
perfectly harmless. There are, however, a few soil bacteria that one is advised to

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