We’ve all seen the photos: turtles with plastic rings around their shells, seals with fishing lines carving deep gashes into their necks, and seabirds with bellies bloated by plastic debris.
The data comes from a survey of 274 experts around the world, as well as 30 years of information on plastic trash collected by the Ocean Conservancy’s International Coastal Cleanup program.
The results stand out from previous studies, which illustrated the abundance and distribution of plastic. “Until now, we haven’t necessarily shown their impact on marine life,” said one of the study’s coauthors, Nicholas Mallos, director of the Ocean Conservancy’s Trash Free Seas Program.
According to the study, the three most deadly forms of plastic identified—buoys, traps, and pots; monofilament fishing line; and fishing nets—all came from fishing vessels. These lost items are frequently referred to as “ghost gear” and can harm marine life for years after they have fallen off a fishing vessel.
“Given that fishing gear is designed to catch animals, and it does that very well, the result isn’t necessarily surprising, but it does suggest that perhaps we need to focus greater attention on reducing the threat of derelict fishing gear on marine species,” Mallos said.
The next-most-deadly items on the list were plastic bags, utensils, and balloons. “Plastic utensils are an item that many people may not think of as posing a threat in a marine environment,” Mallos said. He explained that plastic forks and knives can harm marine life both when they’re whole and later when they break down into smaller, sharper, ingestible pieces.
Cigarette butts and bottle caps—both of which can be mistaken for food—follow. Butts are also the most common item that the Coastal Cleanup program has found on beaches over the past 30 years, Mallos said.
Some animals may also be contaminated by toxins within the plastic, which can travel up the food chain from small animals to larger ones, including humans.
Mallos said the study shows that the need to find new methods to prevent items such as plastic bags and derelict fishing gear from entering the ocean or to reduce their impact on marine wildlife. “A mechanism that prevents ocean plastics from ever reaching these habitats in the first place is absolutely necessary,” he said.