Soil accumulation of microplastics is becoming a pervasive, long-term modifier of terrestrial function. Research led by Markus Rillig at Freie Universität Berlin and by Richard C. Thompson at University of Plymouth establishes that small plastic particles disrupt physical habitats and biological interactions in ways that matter for agriculture, carbon storage, and ecosystem resilience. Understanding how and where these particles enter soils clarifies the pathways to impact and the options for mitigation.
Physical structure and water dynamics
Microplastic particles and fibers alter soil aggregation and porosity by occupying pore space and by interfering with the binding agents that hold soil crumbs together. Work by Markus Rillig at Freie Universität Berlin shows that fibrous microplastics tend to entangle within aggregates, changing pore connectivity and increasing or decreasing water retention depending on fiber shape and concentration. These shifts affect infiltration, aeration, and susceptibility to erosion. In agricultural soils, plastic residues from mulches and irrigation systems concentrate in the plow layer, where even small changes in porosity can modify seedbed conditions and root penetration. The effects are highly context dependent, varying with soil texture, organic matter, and the dominant polymer types present.
Biological communities and nutrient cycling
Microplastics influence microbial communities, soil fauna, and the chemical environment that drives nutrient cycling. Studies by Markus Rillig and colleagues document alterations in microbial respiration and shifts in community composition following microplastic exposure, which can change rates of decomposition and nitrogen mineralization. Soil animals such as earthworms ingest particles, with evidence that this affects growth, feeding behavior, and the movement of material through the soil profile. These biological disruptions cascade into altered carbon turnover and nutrient availability, potentially reducing soil fertility over time. Additive chemicals in plastics and the sorption of pesticides and heavy metals onto plastic surfaces introduce additional chemical stressors that can amplify biological effects.
Consequences extend beyond biogeochemistry to human and cultural systems. Widespread use of sewage sludge and compost containing microplastics has been documented as a major pathway into agricultural lands, a pattern noted by researchers including Richard C. Thompson at University of Plymouth. Regions that rely heavily on recycled biosolids or on plastic-intensive farming practices face higher localized burdens. This creates territorial disparities in soil health and food security risks that intersect with socioeconomic vulnerabilities.
Mitigation requires both reducing inputs and improving monitoring. Source control of single-use plastics, better filtration in wastewater treatment, and changes in agricultural plastic management can limit future accumulation. Targeted soil monitoring, informed by methods developed in the emerging literature, is needed to identify hotspots and to assess trends in soil function. Because evidence varies with polymer type, particle shape, and land use history, management must be adaptive and grounded in local testing. Continued interdisciplinary research led by soil ecologists and environmental chemists is critical to translate mechanistic findings into policies that protect the long-term productivity and ecological integrity of terrestrial soils.