Bioturbation

The mixing and reworking of soil and sediment by the burrowing, feeding and movement of living organisms, from earthworms and ants to burrowing mammals and, in aquatic sediment, worms and shellfish. It disrupts and homogenizes soil layering that would otherwise form through purely physical and chemical processes, aerates and loosens soil to improve water infiltration and root penetration, and is recognized as one of the most significant biological influences on long-term soil structure and development.