What is soil biodiversity and why does it matter?

What is soil biodiversity?

Soil biodiversity is “generally defined as the variability of living organisms in soil and the ecological complexes of which they are part” (Tibbett et al., 2020). Soil organisms are classified according to their dimensions (which is often their width). As a rule of thumb, as soil organisms increase in size, the number of species (diversity) declines (see FAO, ITPS, GSBI, SCBD and EC, 2020, Tibbett et al., 2020).

Soil biodiversity is a major component of global biodiversity (see Eisenhauer et al., 2026). Globally, soils harbour approximately 60% of all species on Earth, based on a recent global review by Anthony et al. (2023), reminding us that much of the planet’s biodiversity exists out of sight, beneath our feet.

The most abundant group of soil organisms consists of microorganisms, which can be grouped into:

• Prokaryotes – organisms whose cells do not have a nucleus, such as bacteria and archaea.
• Eukaryotic microorganisms – organisms whose cells contain a nucleus, including fungi and protists.