In 2025 and 2026, researchers confirmed something that should have been obvious but wasn't: forests are catching microplastics out of the air.
Most microplastics in the environment were assumed to arrive in water. Rivers, runoff, ocean currents. But when scientists examined forest soil and compared it to nearby open land, they found microplastic concentrations were higher in forests, not lower. When they traced the pathway, the mechanism was clear: airborne microplastics drift in the atmosphere globally, including over remote wilderness. When they encounter a tree canopy, the leaves act as a filter. The microplastics settle on the leaves. When it rains, they wash off and fall to the soil. When leaves decompose in autumn, they carry the particles down with them.
Researchers called this the "comb-out effect." The forest is combing microplastics out of the air. A 2026 study found that microplastic concentrations in rural forest soil were higher than in some urban areas. The forests farthest from cities, surrounded by the cleanest-seeming air, are accumulating plastic particles because they are efficient atmospheric filters.
The implications are still being worked out. Forests are storing a new category of pollutant they did not evolve to handle. The question is what this means for soil ecology, root systems, and the organisms living in forest soils. So far: unknown. But the assumption that remote forests are pristine is no longer supportable.
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