Soil biodiversity is essential for most of the ecosystem services and functions that soils
provide and perform. Soil microbes (i.e., bacteria, fungi) and microfauna (i.e., protozoa
and nematodes) transform organic and inorganic compounds into available forms. These transformations are critical for nutrient cycling and availability, for plants, and other species growth, for cycling of soil organic matter and carbon sequestration, and for the filtration, degradation, and immobilization of contaminants in water and soil.

An important part of the food web is represented by mesofauna, such as springtails and mites, which accelerate litter decomposition and enhance nutrient cycling and availability (especially nitrogen), and predators of smaller soil organisms.

Soil macro, and megafauna such as earthworms, ants, termites, and some mammals act as ecosystem engineers that modify soil porosity, water and gas transport, and bind soil particles together into stable aggregates that hold the soil in place and thus reduce erosion.

Soil biodiversity can mitigate threats to ecosystem services, for instance by acting as a powerful tool in bioremediation of contaminated soils. Biostimulation and bioaugmentation are environmentally sound strategies that contribute to the filtration, degradation, and immobilization of target contaminants. Furthermore, the integral use of organisms such as microbes (bioaugmentation), plants (phytoremediation) and earthworms (vermiremediation) as a bioremediation strategy in hydrocarbon-contaminated soils has proven to be a viable alternative for increasing hydrocarbon removal. On the other hand, soil macrofauna, such as earthworms, termites, and ants, play an important role in improving soil structure and aggregation, which can improve resistance to soil erosion caused by wind and water.

Excerpt from FAO, State of Knowledge of Soil Biodiversity, Report 2020