Physical disturbance of an environment by living organisms that changes the order of its components.

In soils, it brings up fragments of the parent rock and buries the organic matter deposited on the surface. Bioturbation counteracts the downward movement of solutes and particles by water and uplifts them towards the roots. Bioturbation mixes soil components, including the organic matter that binds them together. It is therefore a factor in soil stability and fertility.

Burrowing animals play a major role by removing material from their holes and depositing secretions and faeces. Earthworms also mix the soil through their diet: they ingest organic matter, sand to grind it up in their digestive tract and clay to immobilise plant toxins. Their faeces or castings mix undigested organic matter, sand and clay, and when deposited on the surface, they bury freshly fallen plant remains.

Plants contribute to bioturbation, especially in the absence of animals (acid moorland soils, for example). The elements (nitrogen, phosphorus, potassium, trace elements, etc.) taken up by the roots fall back to the soil surface at the death of aerial parts. The roots emit mucilages (which lubricate their growth and retain water) and secretions, particularly antimicrobial one, which account for 10 to 40% of photosynthesis: together with the organic matter of the dead roots, this buries organic matter.

Bioturbation agents create porosity: dead roots and galleries are stable holes that aerate the soil and allow water access. This decompaction compensates for the gravitational collapse of the holes in the soil.

Ploughing is an extreme human bioturbation that increases fertility and buries organic matter. Although it improves physico-chemical fertility in the short term, its intensity alters soil life and therefore biological fertility (including spontaneous bioturbation). It is harmful in the long term by creating unstable porosity and increasing soil erosion by 10 to 100 times.

Agro-ecological systems must encourage bioturbation that can be sustained by soil life.