Atmospheric transport was regarded as a critical route for MNPs contamination in forests (Allen et al., 2019). Anthropogenically generated MNPs from urban/industrial emission sources undergo complex aerodynamic transport processes. These lightweight particles are entrained in atmospheric circulation patterns, with field measurements confirming their presence in precipitation samples from remote alpine regions (e.g., Pyrenees, 2,877 m ASL) at concentrations up to 365 particles/m²/day (Allen et al., 2019). The deposition dynamics encompass both dry (gravitational settling) and wet (precipitation scavenging) mechanisms, with particle form (sphericity, aspect ratio) markedly affecting residence times (Huang et al., 2021). Studies on canopy interception effectiveness indicate that coniferous forests catch more atmospheric MNPs than deciduous trees, attributed to increased surface roughness and wax-mediated adhesive effects (Weber et al., 2023).

The permeability thresholds in forest buffer zones are increasingly influenced by long-term MNP inputs from adjacent anthropogenic systems. Agricultural matrices contribute large numbers of MNPs annually to various environmental compartments through composite pathways: (1) Degradation of low-density polyethylene mulch films releasing MNPs into the forests (Sintim et al., 2020); (2) Biosolid-amended fertilizers containing up to 286 particles/g dry weight (Naderi Beni et al., 2023); (3) Wastewater irrigation delivering 1.0–2.4 × 10⁴ particles/kg effluent (Wu et al., 2024b). These inputs induce measurable pedological alterations, including the reduction in saturated hydraulic conductivity and the decrease of pH value in topsoil horizons. Field experiments demonstrate MP-soil interactions promote aggregate destabilization through weak hydrogen bonding with clay minerals, exacerbating nutrient leaching losses (Elmholt et al., 2008).

In situ MP generation in forest ecosystems follows quantifiable weathering trajectories governed by Arrhenius kinetics. Polymeric materials from tourism debris (PET bottles, LDPE wrappers) and logging residues (PP rope fragments, HDPE fuel containers) undergo sequential degradation: Photo-oxidative cleavage, hydrolytic depolymerization, and mechanical embrittlement (Wu et al., 2024c). Accelerated aging tests indicate high-density plastics (e.g., PET) require 8.3 ± 1.2 years for 50% mass loss under temperate forest conditions, versus 2.1 ± 0.7 years for low-density films (LDPE). Secondary MP generation rates peak with particle size distributions skewing towards environmentally persistent 10–100 μm fractions (Cózar et al., 2014).

MNPs systematically compromise forest ecosystems through multidimensional pathways. In soil systems, MNPs have been certified to reduce macroporosity by 15%–30% and water-holding capacity by 18%–25% via structural disruption, while their hydrophobic surfaces amplify contaminant bioavailability (Schefer et al., 2025). Wang et al. (2024) determined the concentration dependent effects of PVC MNPs on affecting the physicochemical characters of soils with various soil textures. The soil texture should be a key issue affecting their pore connectivity, especially for sandy and sandy loam soils. The results may be attributed to the following mechanisms: First, the MNPs could occupy the pore spaces of soil and create disconnected voids, thereby reducing the pore connectivity and effective porosity (Schefer et al., 2025). Second, many types of MNPs are hydrophobic, which could decrease the soil water affinity, thereby disrupting capillary forces that stabilize pore networks (Shafea et al., 2023). Third, the fate of MNPs in soil could also influence its connectivity by inhibiting the soil fauna and adsorbing other chemicals to form MNP-aggregate complexes (Schefer et al., 2025).

Concurrently, sublethal MP exposure suppresses microbial functions: nitrogen-fixing bacteria exhibit 40%–60% reduced nifH expression, correlating with 22%–35% declines in nitrogen mineralization, while arbuscular mycorrhizal fungi show 30%–50% fewer root-colonizing hyphae, impairing phosphorus uptake (Aralappanavar et al., 2024). Metagenomic shifts further reduce extracellular enzyme activity.

Plant physiology is equally compromised—MPs (10–300 μm) adhere to roots via electrostatic forces, reducing absorptive surface area and hydraulic conductivity (Sun et al., 2020), while sequestered Fe³⁺/Zn²⁺ induces micronutrient deficiencies. Leached additives like Di (2-ethylhexyl) phthalate trigger root ROS surges (H₂O₂), causing mitochondrial damage and stunting conifer growth (Wu et al., 2022a). Soil invertebrates face acute toxicity: earthworms ingesting 5–20 μm MPs endure gut epithelial damage, reducing cast production by 35%–60%, while collembola suffer 50% mortality and 65%–80% egg reduction at 100 mg/kg MPs (Guo et al., 2023).

Trophic transfer escalates risks—birds accumulate 12–45 particles/g in gizzards, and tertiary consumers like martens ingest DDT-laden MPs. Critically, MNPs synergize with climate stressors: MNP-contaminated soils desiccate faster during droughts, advancing tree wilting, while suppressed jasmonic acid signaling in oaks increases herbivory. MNPs also lower lignocellulose ignition temperatures, accelerating crown fires, and release toxic acrylonitrile upon combustion, compounding post-fire ecotoxicity (Jin et al., 2024). This cascade of impacts underscores MPs as a keystone stressor in Anthropocene forest decline.

As for MNPs in forest ecosystems, several actions for decreasing MNP threats to forest ecosystems could be discussed as follows: First, it is of great importance to develop standardize microplastic collection process, consistent monitoring protocols specific to forest environments including harmonized methodologies for soil core sampling, canopy particle collecting, and hyperspectral detection of MNPs in organic matrix to produce comparable baseline data. Meanwhile, the ecotoxicological thresholds and species specific resistance can be determined by controlled mesocosm experiments, such as the gradient MNP concentrations from (0.1%–10% w/w), exploring the nutrient or contaminants transferring. In addition, critical research gaps requiring urgent attention on nanoparticle mobility in root systems, polymer-specific adsorption dynamics in humic soils, and co-stressor interactions (e.g., drought or heavy metals).

Scientific insights must inform policy reforms, such as phasing out non-degradable agricultural mulch films (with subsidies for biodegradable alternatives), mandating wastewater treatment upgrades to capture sub-micron particles (prioritizing plants near old-growth forests), and integrating MNP surveillance into protected area management plans (e.g., IUCN Category II forests). Plastic influx can be decreased while promoting stewardship through parallel public engagement projects aimed to communities near forests, such as bilingual workshops on reusable alternatives to single-use plastics and citizen science initiatives for litter audits. Parallel public engagement campaigns targeting forest-adjacent communities—via multilingual workshops on reusable alternatives to single-use plastics and citizen science programs for litter auditing—can reduce plastic influx while fostering stewardship. By synergizing robust science, evidence-based governance, and grassroots behavioral change, this multipronged strategy offers a pathway toward mitigating MNP-driven forest degradation.