Microplasty has long been omnipresent: the tiny plastic particles can be demonstrated everywhere on earth – from mountain peaks to the deep sea. They are mainly transported through air and water and, where they accumulate, can damage complete ecosystems. Researchers have now been able to show for the first time that microplastics are also accumulated in forest floors – with potentially fatal consequences for the forests already weakened by climate change.
Plastic is hard to imagine from our everyday life – and that leaves traces in the environment. Large plastic parts disintegrate over time to tiny particles or the plastic is made directly in microscopic size, for example as part of cosmetics. Such microplastic particles can now be found almost everywhere: in seas, lakes, air and even in human blood. They are only slowly dismantling and can cause considerable damage wherever they accumulate. Knowing where and in what amounts of microplastics end up in the environment is therefore crucial in order to better assess the risks of ecosystems and health.
Scientific forest walks
So far, studies on microplastic pollution have concentrated, especially on urban and agricultural soils, while forests were mostly not given little attention. In order to close this gap, Collin Weber and Moritz Bigalke from the Technical University of Darmstadt have now systematically examined whether and to what extent microplastics also reaches forest soils. For this, the team took rehearsals at four forest locations east of Darmstadt.
Both the upper layers of the floor as well as fallen leaves and the so -called atmospheric deposition – particles come from the air to the surface of the earth were examined. With the help of models, the researchers were also able to estimate how much microplastics since the 1950s could theoretically have been entered in the forest floors over the air and how the particles would then have distributed themselves in different layers of soil.
Don’t see the forest for plastic
The result: Microplasty was demonstrated in the forest floor at all locations examined. “The microplastic coentations of the forest soils examined ranged from 120 to 13,300 particles per kilogram, the average was 4,440 particles per kilogram of forest floor,” report Weber and Bigalke. As they found out, the particles accumulate particularly strongly in the upper layers of leaves, but also penetrate in deeper layers of soil. The study thus provides the first proof that tiny plastic particles are also deposited in forest floors. And this deposition could have devastating consequences: “Forests are already at risk from climate change, and our results suggest that microplastics could now also be an additional risk to forest ecosystems,” says Weber.
But how does the microplasty get into the forest floor? “Our results indicate that microplastics in forest soils primarily come from atmospheric deposits and the falling leaves,” explains Weber. “The microplastics from the atmosphere first settles on leaves of the treetops. Then the particles in deciduous forests are transported onto the forest floor, for example, by rain or the autumn leaves.” In the examined forest pieces, an average of around nine microplastic particles per day and square meters set out from the atmosphere. In order to explain the plastic amount measured in the forest floor, this amount should have been deposited on the ground for 70 years. “But there could also be additional microplastic sources,” emphasize the researchers. These include, for example, plastic films and other plastic objects from forestry, but also plastic waste from forest visitors. In deeper layers, the tiny plastic particles probably get through the decomposition of the foliage and through activities of soil organisms that further distribute the particles.
Source: Technical University of Darmstadt; Specialist articles: Nature Communications Earth & Environment, DOI: 10.1038/S43247-02712-4
