Microplastics and nanoplastics—long known to pollute oceans, rivers, and agricultural land—are now confirmed to be accumulating in forest ecosystems as well. A new study from geoscientists at TU Darmstadt, published in Nature, reveals that forests are quietly storing airborne plastic particles in their soils, raising fresh concerns about environmental and health risks.
According to the team, the majority of microplastics enter forests through atmospheric deposition. These particles settle on tree leaves and are later transported to the forest floor by rain or the fall of leaves.
“The microplastics from the atmosphere initially settle on the leaves of the tree crowns, which scientists refer to as the ‘comb-out effect’,” according to lead author Dr Collin J. Weber from the Institute of Applied Geosciences at TU Darmstadt: “Then, in deciduous forests, the particles are transported to the forest soil by rain or the autumn leaf fall, for example.”
Once in the soil, leaf decomposition plays a critical role in trapping the pollutants. The study found the highest concentrations of microplastics in the upper layers of leaf litter, though significant amounts were also discovered deeper underground. These deeper deposits are likely driven by the decomposition of organic matter and the activity of soil organisms that break it down.
To conduct the study, researchers collected samples from four forest sites east of Darmstadt, Germany. Using a newly refined analytical technique, they measured microplastic concentrations in soil, fallen leaves, and atmospheric deposition. Spectroscopic methods were then used to chemically analyse the samples. The team also developed a model to estimate atmospheric microplastic inputs since the 1950s, which helps quantify the long-term accumulation in forest soils.
“Our results indicate that microplastics in forest soils originate primarily from atmospheric deposition and from leaves falling to the ground, known as litterfall. Other sources, on the other hand, have only a minor influence,” Weber notes. “We conclude that forests are good indicators of atmospheric microplastic pollution and that a high concentration of microplastics in forest soils indicates a high diffuse input – as opposed to direct input such as from fertilisers in agriculture – of particles from the air into these ecosystems.”
This marks the first study to establish a direct link between airborne microplastics and their storage in forest soils, a topic previously unexplored in scientific literature. The findings provide a new perspective for evaluating the environmental risks associated with airborne plastic pollution. “Forests are already threatened by climate change, and our findings suggest that microplastics could now pose an additional threat to forest ecosystems,” says Weber, adding that the research may also have implications for human health, as it underscores the global transport of microplastics through the air—potentially affecting the air we breathe.
For more information: “Forest soils accumulate microplastics through atmospheric deposition” by Collin J. Weber and Moritz Bigalke, 26 August 2025, Communications Earth & Environment. DOI: 10.1038/s43247-025-02712-4.
