At the heart of these interactions lies the ability of microplastics to alter the quality and quantity of SOC through various mechanisms. Microplastics, often accompanied by a mixture of co-occurring contaminants, leach dissolved organic matter (DOM) into the soil environment, thereby modifying the native soil organic carbon pools. This leaching process influences microbial communities and their metabolic activities, which are central to carbon cycling. By affecting the mineralization of native SOC, microplastics potentially disrupt the natural microbial carbon pump (MCP), a mechanism by which microbes convert labile organic compounds into more stable, mineral-associated organic carbon fractions, essential for long-term carbon storage in soils.

Recent studies underscore that the microplastic surfaces form unique microhabitats, adsorbing dissolved organic matter with considerable affinity. This adsorption not only sequesters DOM but creates hotspots for mineral-organic matter interactions that are fundamental to SOC stabilization. These hotspots enhance the formation of soil aggregates—structural units in which organic matter can be physically protected from microbial decomposition. The presence of microplastics within these aggregates alters their physical properties and the spatial organization of carbon pools, consequently reshaping carbon storage dynamics on soil micro-scales. Such changes could have cascading effects on soil carbon turnover rates and, by extension, on global carbon budgets.

Moreover, the physicochemical characteristics of microplastics—such as size, polymer type, and surface chemistry—critically determine their impact on SOC. For instance, smaller microplastics with higher surface areas may provide more adsorption sites and thus stronger interactions with organic matter and minerals. Conversely, polymer types with varying hydrophobicity and chemical stability influence the interactions differently, potentially affecting the release of additives or adsorbed pollutants that further perturb microbial processes. This complex mosaic of factors necessitates a multi-disciplinary approach combining soil science, microbial ecology, and polymer chemistry to unravel the nuanced role of microplastics in terrestrial carbon dynamics.

Adding a geochemical perspective, microplastics influence the redox status and mineral speciation within soils, which are central to the stabilization or mobilization of organic carbon. The alteration of mineral surfaces caused by microplastic presence can change the binding affinity for organic matter, thereby affecting the formation of mineral-associated organic carbon (MAOC), one of the most stable forms of soil carbon. These effects, compounded by variations in soil type and environmental conditions, mean that the role of microplastics in SOC sequestration varies spatially and temporally, complicating efforts to predict their long-term impacts on global carbon cycles.

From a biological viewpoint, the disruption of microbial communities by microplastics is profound. Microorganisms drive key transformations in soil carbon, from decomposition to carbon stabilization. When microplastics introduce physical barriers, toxic chemicals, or change the soil’s hydrophobicity, they modify microbial community structure, diversity, and function. This can lead to either a suppression or stimulation of SOC mineralization, depending on the environmental context and microbial taxa involved. Such microbial shifts bear significant implications for carbon fluxes, as microbial biomass and exudates are critical components in soil carbon stabilization processes.

One of the striking revelations in this field is the dual role of microplastics as both disruptors and facilitators of soil carbon processes. Although they may expedite the degradation of some organic compounds, increasing carbon release as CO2 or methane, they simultaneously present novel substrates for carbon adsorption and protection. This paradox underscores the complexity of microplastic impacts—wherein the net effect on soil carbon stocks depends on the balance between enhanced mineralization and augmented sequestration pathways. Understanding this balance requires dissecting the interplay of microplastic characteristics, soil properties, and microbial ecology.

This nuanced understanding brings to light an urgent need for integrating microplastic considerations into models of soil carbon cycling and climate projections. Current models often overlook microplastic-mediated processes, potentially underestimating or misrepresenting soil carbon dynamics. Incorporating the effects of microplastics on DOM leaching, microbial community shifts, mineral interactions, and physical soil structure can refine predictions of SOC sequestration potentials and carbon emissions under future environmental scenarios.

Furthermore, the implications extend beyond soil carbon stocks to the broader goals of mitigating climate change and achieving carbon neutrality. Soils constitute a massive reservoir of terrestrial carbon, and perturbations in their carbon sequestration ability could amplify atmospheric carbon emissions, offsetting global mitigation efforts. The prevalence of microplastics in soils—stemming largely from agricultural plastics, wastewater, and atmospheric deposition—means that addressing their impact is inseparable from sustainable soil management and climate strategies. Without concerted action, microplastic pollution may undermine soil health and the planet’s natural capacity to regulate greenhouse gases.

Technological advancements in analytical chemistry and molecular biology are pivotal in advancing this research frontier. Techniques such as high-resolution mass spectrometry, isotope tracing, and metagenomics allow for detailed characterization of microplastic-associated organic matter, microbial responses, and mineral-organic matter interactions at unprecedented scales. These tools facilitate the disentanglement of complex biogeochemical processes, promoting mechanistic insights rather than correlative observations, crucial for developing mitigation measures and policy interventions.

As the literature evolves, the scientific community emphasizes urgent interdisciplinary collaboration to address the ecological consequences of microplastic contamination. Bridging knowledge from polymer science, soil ecology, climate science, and environmental policy is vital for crafting holistic solutions. Moreover, public awareness and regulation of plastic usage, waste disposal, and soil protection must integrate findings on soil carbon-microplastic interactions to safeguard terrestrial ecosystems and their climate function.

In summary, emergent evidence points to microplastics as potent modifiers of soil carbon dynamics with far-reaching consequences for ecosystem function and climate regulation. Their impact manifests through leaching dissolved organic matter, disrupting microbial carbon processing, altering mineral and aggregate soil structures, and changing the balance between carbon release and sequestration. Addressing these multifactorial effects is imperative for advancing soil science and environmental stewardship in an era where plastic pollution intersects with climate change challenges. Future research must unravel these complex mechanisms across spatial and temporal scales to effectively integrate microplastic influences into soil carbon management paradigms and global climate models.

The exploration of microplastics in terrestrial soils represents a frontier in environmental science—revealing how anthropogenic materials permeate foundational Earth processes. The dynamic interactions between microplastics and organic carbon cycles not only deepen our understanding of soil ecology but also critically inform global carbon management strategies. As humanity grapples with concurrent environmental crises, the intersection of plastic pollution and soil carbon underscores the interconnectedness of human activity and planetary health, calling for transformative approaches in research, policy, and public engagement to foster resilience in Earth’s essential systems.

Subject of Research: Impacts of microplastics on terrestrial soil carbon dynamics

Article Title: Impacts of microplastics on terrestrial soil carbon dynamics

Article References:
He, G., Lu, M., Yang, Y. et al. Impacts of microplastics on terrestrial soil carbon dynamics. Nat. Geosci. (2026). https://doi.org/10.1038/s41561-026-01935-0

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41561-026-01935-0

Soils globally harbor more than twice the amount of carbon stored in Earth’s atmosphere, making them formidable regulators of atmospheric CO₂ concentrations. The balance between carbon uptake and release by soils thereby plays a pivotal role in modulating climate. However, understanding soil carbon sensitivity to environmental changes, particularly in warmer regions, has remained a daunting challenge. This new study unpacks this complexity by focusing on subtropical and tropical ecosystems where vast reservoirs of organic carbon reside, yet the dominant factors influencing their carbon turnover rates have been contested for years.

Previous investigations underscored the importance of permafrost soils in the context of climate change, showing how rising temperatures there induce thawing and the consequent release of trapped carbon. While permafrost feedbacks have gained substantial attention, the behavior of soil carbon under warming in warmer climates remained less defined. Microbial activity in subtropical and tropical soils, known drivers of organic matter decomposition, are known to be sensitive to humidity and temperature, but the relative weight of these factors in controlling carbon release has defied consensus. Some researchers argued that changes in hydroclimatic conditions drive soil carbon dynamics, while others posited temperature as the chief determinant.

In an innovative departure from conventional studies that observe soil processes in situ, the research team adopted a long-term, sedimentary record-based approach. They investigated organic material transported by the Nile River from soils across a vast catchment area spanning subtropical to tropical north-east Africa to its deposition site off the eastern Mediterranean coast. By analyzing marine sediment cores that accumulate land-derived organic carbon over millennia, they accessed a historical archive stretching back 18,000 years, from the terminal stage of the last ice age to present-day conditions. This method allowed them to reconstruct changes in soil carbon turnover rates under varying climatic regimes over geological timescales.

Dr. Vera Meyer, the study’s lead author, explains the reasoning behind the choice of proxy: “Our approach hinges on assessing the age of organic matter delivered by the Nile, which encodes how long carbon spent in soils as well as its downstream transit time. This dual factor record offers an integrative perspective on soil carbon processing beyond the fleeting snapshots afforded by direct soil observation.” Such insights from sedimentary archives provide a window into climate-carbon interactions that modern soil experiments cannot easily achieve.

The researchers’ analysis revealed a striking and unexpected pattern: the age of terrestrial carbon reaching the Mediterranean shifted minimally in response to precipitation variability and runoff fluctuations but changed markedly in alignment with temperature increases. In particular, the warming phase following the last glacial maximum induced a far more pronounced acceleration in soil organic matter decomposition than predicted by prevalent Earth system models. This indicates that microbial-mediated carbon turnover in these subtropical and tropical soils is dominantly controlled by temperature, challenging earlier assumptions that hydrological variations are equally or more influential.

Co-author Dr. Enno Schefuß emphasizes the magnitude of this effect by stating that post-glacial warming triggered a significant surge in soil-derived CO₂ emissions that outpaced existing model projections. The rapid microbial respiration under warmer conditions effectively contributed to the rising atmospheric CO₂ concentrations documented at the end of the ice age, depicting a powerful feedback mechanism between soils and climate. This realization demands urgent re-evaluation and refinement of biogeochemical models to more accurately represent temperature sensitivities in diverse soil ecosystems.

Additionally, as Dr. Peter Köhler from the Alfred Wegener Institute highlights, the underestimation of soil carbon release in climate models not only obscures our understanding of past carbon cycle dynamics but also jeopardizes the reliability of future climate predictions. Current projections may significantly undervalue the extent of positive soil carbon-climate feedbacks that could accelerate global warming, underscoring the importance of integrating empirical paleoenvironmental data into model development.

The implications of these findings extend well beyond academic debate. By confirming that temperature exerts a dominant control over soil organic carbon turnover in (sub-)tropical regions, the study warns of a potentially intensified cycle of carbon release as global temperatures rise in the coming decades. Given the massive carbon stocks stored in these soils, even subtle accelerations in decomposition rates could amplify atmospheric CO₂, thereby fueling further warming in a self-reinforcing loop. This feedback poses an additional challenge to climate mitigation efforts and highlights soils as a critical but vulnerable component of the Earth system.

Moreover, the long-term perspective afforded by sediment core analysis brings to light the evolutionary trajectory of soil carbon responses to natural climate variability. It showcases the intrinsic connection between soil microbial communities and ambient temperatures over millennial timescales, a relationship progressively disrupted by anthropogenic influences. Understanding these temporal dynamics is essential for anticipating how terrestrial carbon reservoirs will fare under unprecedented rates of climate change.

The study was conducted under the auspices of the Cluster of Excellence “Ocean Floor – Earth’s Uncharted Interface” at MARUM, aimed at unraveling the fate of carbon from multiple sources in marine environments. By bridging terrestrial and marine perspectives, researchers are better positioned to map the pathways through which soil carbon exits terrestrial ecosystems and enters the ocean-atmosphere carbon cycle. Such interdisciplinary efforts advance holistic climate science, integrating geochemical, microbiological, and geological viewpoints.

In summary, this research reframes the narrative on tropical and subtropical soil carbon dynamics by unequivocally placing temperature at the helm of controlling organic matter turnover. Its robust evidence from paleoenvironmental archives challenges prevailing models, calls for their recalibration, and raises critical awareness of soil carbon’s role in amplifying ongoing climate change. As global temperatures climb, the findings underscore the urgency of incorporating soil carbon feedbacks into climate policy discussions and environmental management strategies.

Subject of Research: Soil carbon turnover dynamics and the influence of temperature in subtropical and tropical soils over geological timescales.

Article Title: Dominant Control of Temperature on (sub-)tropical soil carbon turnover

News Publication Date: 15-May-2025

Web References:
http://dx.doi.org/10.1038/s41467-025-59013-9

Image Credits: MARUM – Center for Marine Environmental Sciences, University of Bremen; V. Diekamp

Keywords: Earth sciences, Climatology, Earth systems science, Geochemistry, Oceanography, Earth climate, Paleoclimatology