A taxonomy-inspired hierarchical classification of plastic litter

Plastic pollution represents one of the most pervasive and persistent material signatures of the Anthropocene, yet its scientific characterization remains fragmented across material-, size-, and compartment-based classification schemes. Although operationally effective, these approaches fail to capture plastics as structured anthropogenic entities embedded within coupled human–Earth systems. Here, we introduce the Taxonomy-inspired Hierarchical Classification of Plastic Litter (THCPL), a hierarchical and integrative classificatory framework that organizes plastic litter from broad material context to specific marketed products, explicitly linking material composition, functional form, industrial origin, market identity, and environmental persistence. THCPL is structured across six taxonomic levels (Phylum, Class, Order, Family, Genus, and Species) using biological taxonomy strictly as a structural analogy, while maintaining clear ontological and epistemological boundaries between living systems and industrial artifacts. Grounded in Earth system science and Anthropocene research, the framework is designed to preserve scalability, traceability, and analytical coherence under real-world field conditions, including fragmentation and weathering. The operational feasibility and transferability of THCPL are demonstrated through its application to standardized coastal litter datasets from six countries (Brazil, Colombia, Italy, Morocco, Panama, and Spain), encompassing 912 plastic items across diverse coastal typologies and socio-environmental contexts. Across all regions, THCPL enabled consistent hierarchical resolution, revealed high producer- and brand-level richness, and supported robust cross-regional comparison, even when fine-scale identification was constrained. Beyond classification, THCPL provides a foundational structure for quantitative analysis, enabling diversity, dominance, and functional assessments, forensic source attribution, and policy-relevant evaluation without normative assumptions. By aligning environmental observations with governance instruments such as Extended Producer Responsibility and by offering a structured framework for interpreting plastics as future technofossils, THCPL advances the integration of plastic pollution research into Earth-system monitoring, environmental governance, and Anthropocene stratigraphy.