Transition to bio-based plastic packaging reveals complex climate-biodiversity trade-offs.

Plastics are a major contributor to global greenhouse gas emissions and biodiversity loss, with packaging accounting for around 40% of European plastic production. Bio-based plastics are often promoted as a climate-friendly alternative, yet their broader environmental implications remain unclear. Here, we conduct a harmonized life cycle assessment of fossil- and bio-based plastic packaging, integrating end-of-life fate and plastic leakage. We find that while bio-based plastics reduce greenhouse gas emissions, they increase ecosystem damage, primarily driven by land use. At the product level, outcomes are sensitive to feedstock origin and waste management. When mismanaged, environmentally persistent bio-based plastics contribute substantially to ecosystem damage. Scaling scenarios for Europe show that even complete substitution with bio-based plastics cannot offset the environmental burden of continued demand growth. Only strong demand-side measures, particularly demand reduction and improved circularity, can mitigate trade-offs across climate change and biodiversity, calling for a shift from material substitution to systemic interventions in production and consumption.