The world’s oceans are increasingly inundated with plastic, a situation scientists say is worsening. This material poses multiple threats to marine life: animals can become ensnared, ingest it, or be exposed to its toxic chemicals. Once swallowed, plastic can persist within an animal, potentially obstructing vital passages like airways or digestive tracts.
A comprehensive international agreement to control plastic production and waste management offers a potential solution. Despite recent treaty negotiations facing challenges, scientists continue to explore effective frameworks. To strengthen such an accord, evidence-based data on lethal plastic quantities for marine species is crucial. Consequently, a research team, whose findings were published in the journal Proceedings of the National Academy of Sciences, analyzed over 10,000 autopsies of sea turtles, seabirds, and marine mammals. Their investigation revealed that although the precise amount of plastic causing death differs across species, the critical thresholds are frequently alarmingly low.
By examining animal death records spanning over a century, the researchers ascertained both the volume of plastic ingested by creatures and its role in their demise. Erin Murphy, manager of ocean plastics research at the Ocean Conservancy and a study co-author, explained that they subsequently quantified the plastic amounts associated with a 50% and a 90% probability of death. The team also investigated various plastic types to identify which posed the greatest risks to specific animal groups.
“I was surprised by some of the thresholds we found,” expressed Murphy. Based on the team’s computations, an Atlantic puffin-sized bird consuming less than the equivalent of three sugar cubes’ worth of plastic faced a 90% likelihood of death due to plastic ingestion. For a Loggerhead sea turtle, a fatal amount approximated the volume of two baseballs.
The study also revealed that rubber materials pose a distinct danger to birds. Murphy stated, “For seabirds, consuming as few as six pieces of rubber, like fragments of a balloon—each typically smaller than a pea—carries a 90% probability of being fatal.” (While rubber has natural origins, a significant portion currently in use is synthetic and could fall under the purview of a plastics treaty.)
This analysis specifically concentrated on cases where plastic was unequivocally identified as the cause of death—for example, by obstructing airways, rupturing stomachs, or tearing intestines. It is also probable that plastic contributes to other, less apparent issues for marine animals, such as inducing a false sense of satiation despite insufficient nutritional intake.
“It’s a sad and difficult thing to think about, but it’s also a reminder that everyone can be part of the solution,” Murphy acknowledged. She asserted, “To truly tackle this issue, the scientific evidence is unambiguous. We must curtail plastic production, enhance waste collection and recycling efforts, and remove existing plastic pollution. These are endeavors everyone can participate in.”
To minimize plastic consumption in daily life, individuals can opt for solid shampoo and conditioner bars over bottled products, choose unpackaged fruits and vegetables instead of those wrapped in single-use plastic, and exercise caution regarding plant-based alternative plastics—.
Murphy also recommended picking up plastic debris encountered during daily routines. Each piece properly disposed of means one less item potentially harming a sea turtle.
