Integrating plastic ingestion impacts into biodiversity metrics: a global effect factor for marine air-breathing vertebrates

Plastic debris ingestion poses an important and escalating threat to marine biodiversity. This includes both impacts from macro- and from microplastics. For macroplastics, impacts can, for example, stem from entanglement or ingestion of plastic pieces. In sustainability assessment tools, such as Life cycle assessment (LCA), attempts to include impacts from entanglement exist. However, although ingestion has been extensively documented across taxa and ocean basins, this critical impact pathway remains largely absent from Life Cycle Assessment. To contribute to closing this gap, we developed a global effect factor (EF) that quantifies the potentially affected fraction (PAF) of species impacted by macro- and micro-plastic ingestion in marine air-breathing vertebrates (seabirds, marine mammals, and sea turtles).

We compiled and harmonized population-level ingestion data from 284 peer-reviewed studies encompassing 308 species and over 55,000 individuals. Based on the known distribution ranges of individual species, exposure to floating marine plastic debris was estimated across eight major ocean basins. Species-specific dose–response relationships linking ingestion prevalence to plastic concentration were then established and used to construct a field-based Species Sensitivity Distribution (SSD). From this, we derived a hazardous concentration affecting 20 % of species above a 10 % ingestion threshold (HC20 = 51.7 kg km⁻³) and a corresponding EF of 3.87 × 10⁻³ PAF km³ kg⁻¹.

Sensitivity analyses confirmed that the EF remained consistent within the same order of magnitude under varying modeling assumptions, supporting its robustness and transferability. This EF enables the explicit inclusion of plastic ingestion impacts in Life Cycle Impact Assessment (LCIA) as a new distinct pathway of physical harm, complementing existing models for entanglement and ingestion of microplastics.

By translating empirical field data into a quantifiable biodiversity impact metric, our study provides an essential bridge between measurements, indicators, and decision-making tools. Integrating such metrics will enhance the capacity of sustainability assessments to reflect the true ecological costs of plastic pollution.