An estimated 8–12 million metric tonnes of plastic enters the ocean annually. The cumulative stock of plastic in the ocean is estimated at 150–200 million metric tonnes. This plastic does not disappear — it breaks into smaller and smaller fragments (microplastics and nanoplastics) while retaining its polymer structure for decades to centuries.
The welfare impact of ocean plastic on marine wildlife is documented across hundreds of species. A landmark 2015 study found plastic in 90% of seabirds examined; a 2023 update estimates 99% of seabird species are now exposed. Sea turtle studies find plastic ingestion in over 50% of individuals in many populations. Marine mammals — including sperm whales, beaked whales, dolphins, and seals — are found stranded with stomachs full of plastic debris. The suffering associated with these exposures ranges from subtle physiological effects to acute, prolonged death.
Entanglement in plastic debris — particularly ghost fishing gear (abandoned, lost, or discarded fishing nets and lines) — is one of the most severe wildlife welfare issues in the ocean. Entangled animals experience: progressive constriction of limbs or bodies as they grow; drowning (for air-breathing marine mammals and sea turtles); wounds from cutting or abrasion; starvation from inability to feed; and exhaustion from dragging gear.
Ghost gear kills an estimated 136,000 marine mammals and sea turtles and millions of seabirds annually (Global Ghost Gear Initiative estimate). Species particularly affected include: humpback whales (entangled in crab pot buoy lines), northern right whales (critically endangered, frequently entangled in lobster and crab trap lines), Hawaiian monk seals, and fur seals.
Responses include: ghost gear retrieval programs (Global Ghost Gear Initiative coordinates retrieval globally); fishing gear marking requirements enabling identification of source vessels; weak links that allow gear to break free under cetacean pressure; and Ropeless fishing technology (buoys that rise to the surface on acoustic command, eliminating vertical lines). Maine and other US lobster fishing regions are piloting ropeless fishing to protect critically endangered North Atlantic right whales.
Plastic ingestion affects seabirds, sea turtles, marine mammals, and fish. Ingested plastic causes:
Laysan Albatross chick mortality from plastic ingestion is a documented welfare emergency — parent birds mistake floating plastic for prey and feed it to chicks at Midway Atoll and other nesting sites. Chick bodies are found with stomachs full of plastic caps, cigarette lighters, and fishing line. NOAA and partner organizations conduct nest monitoring and limited chick intervention at Midway to reduce plastic-related mortality.
Microplastics (particles under 5mm) are present throughout the marine environment — in open ocean surface water, deep sea sediments, and within the bodies of marine organisms at every trophic level. Their welfare implications are increasingly researched:
The most significant regulatory development for ocean plastic welfare in 2025 is the ongoing negotiation of a global plastics treaty under UNEP. Negotiations are proceeding through Intergovernmental Negotiating Committees (INCs); INC-5 concluded in late 2024 with significant remaining gaps between countries favoring production limits and those favoring waste management approaches.
A strong global plastics treaty — with production reduction, design standards (eliminating problematic polymers), extended producer responsibility, and waste management requirements — would represent the most significant structural intervention available to address ocean plastic wildlife welfare at scale. The treaty's ambition will determine its wildlife welfare impact.
Beyond the treaty, responses in 2025 include:
Tags: Ocean Plastic Marine Wildlife Entanglement Microplastics Treaty 2025