It’s long been known that plastics in the ocean threaten the health and survival of marine species, but a new study now reveals what types of plastic are most dangerous, and which animals are most at risk.
After reviewing hundreds of scientific articles and studies, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), an Australian government agency, found that plastic bags and flexible packaging are the deadliest plastic items in the ocean.
Discarded fishing line and nets, as well as latex gloves and balloons, were also found to be disproportionately lethal when compared with other ocean debris that animals mistakenly eat, according to the study published this month in the journal Conservation Letters.
“Death from eating any of these items is not a quick one and it is not likely to be painless,” Lauren Roman, a marine ecologist who led the study, told the Guardian. “It’s a pretty awful way to die.”
The CSIRO researchers analyzed 655 scientific articles about marine debris and 79 studies detailing deaths in marine species. Through this review, they found that ingesting plastic was responsible for deaths across 80 species, including whales, dolphins, turtles, seabirds, seals, and sea lions.
Whales, dolphins, and turtles were especially vulnerable to eating plastic film. Seabird deaths were often linked to the ingestion of hard plastic pieces and balloons. As for seals and sea lions, fishing lines and nets were found to be the most lethal type of plastic to those species.
“For the first time we have quantified what’s being eaten, what’s deadly, and then [are going to] see which [of the items] can be controlled through policies,” Roman said.
This is especially important because while there is a lot of plastic in the ocean, some types are more harmful than others.
Rubber, for instance, was revealed to be the most disproportionately lethal. Flexible plastic used for bags and packaging are also especially dangerous since they are so widespread and can crumple up to create blockages in an animal’s digestive system.
The deaths of these marine species are a part of the larger picture of biodiversity loss due to man-made causes, such as land and water pollution, which disproportionately impact the world's most marginalized communities. Biodiversity forms the foundation of human society by providing clean air and water, soil that fosters food production, a stable climate, and much more.
In light of the review, the researchers recommended that policymakers focus on the reduction of plastics through regulation, bans, and replacement of items that have shown to result in high mortality.
Many companies and countries have taken steps to reduce single-use plastic in recent years. Most recently, in October, England officially banned plastic straws, drink stirrers, and cotton buds.
But the COVID-19 pandemic has likely led to an increase in plastic use, according to Richard Leck, head of oceans at World Wildlife Fund Australia.
“This study shows us we have to get that momentum back,” he told the Guardian. “It’s important to remember what happens to these animals when they ingest these plastics. It’s a horrible death. When turtles ingest plastic bags they can’t submerge. Marine mammals waste away over weeks and weeks.”
The flow of plastic into the ocean is expected to triple by 2040 if current trends continue, reaching up to 29 million metric tons a year. With more plastic in the ocean, marine animals will face higher risks of its lethal effects.
Support for the United Nations’ global treaty to tackle plastic pollution has grown to include two-third of member states. However, the US and the UK — the two biggest per capita waste producers, according to the Guardian — have not yet shown support for the treaty or called for a new agreement.