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In 1938, American biologist Eugene Gudger documented an Atlantic cod with its head stuck in a syrup can. Eleven years later, he recorded a tiger shark that had horseshoes, metal cans, and rope in its stomach. Perhaps unsurprising now, but Gudger’s findings were among the first scientifically noted instances of marine animals inadvertently eating or becoming entangled in human rubbish.
“Back then, people believed that things they throw in the ocean would disappear entirely, diluted in the infinite water,” says Susanne Kühn, a biologist at Wageningen Marine Research in the Netherlands. “I think Gudger’s observations were a first hint that this perception is incorrect, and problems today prove him right.”
Today, 914 marine species have been documented either entangled in human trash or with it lodged in their digestive tracts. Kühn and her colleague Jan Andries van Franeker tallied this figure by analyzing 747 scientific studies published from May 2019 all the way back to Gudger’s 1938 report.
Among these 914 species are 226 of the 409 recognized seabirds. The first animal ever scientifically recorded eating plastic was a Leach’s storm petrel in 1962. Out of 43,525 individual seabirds studied, more than a quarter have been afflicted by plastic. The most vulnerable are tube-nosed seabirds, including petrels and albatrosses, of which nearly 42 percent contained plastic.
“These birds are opportunistic surface feeders and they are not picky when it comes to food,” explains Kühn. “This should give us reason to worry, as these birds are particularly prone to other human-related risks such as by-catch, overfishing, and climate change.”
All seven sea turtle species have eaten or been ensnared in plastic. Only 59 of 86 whale species have been studied, but all of those that were have been affected. Of the 31 seal species, 22 have been found with plastic. Seals also seem particularly susceptible to entanglement, possibly due to their curiosity.
Perhaps the most unusual case was when large goosefish were documented to have eaten little auks that had eaten plastic. “It’s a spectacular example of secondary ingestion and an interesting case of fish eating birds,” Kühn says.
Some of the most surprising swallowed items—found in herring gulls in a 2008 study—included a plastic winner medal (complete with ribbon), an entire mobile phone, and an army of toy soldiers.
Similar reviews conducted in 1997 and 2015 put the number of affected species at 267 and 557, respectively. The latest figure of 914 suggests a rapidly rising trend. Most of the newcomers to the list are fish, with the number affected jumping from 166 to 430 out of the 31,243 known species. This surge likely reflects a growing interest from researchers.
But Kühn notes that drawing deep meaning from the data is difficult, given that it takes just one affected individual to add its species to the list. For example, only one blue whale has been analyzed for contamination, which doesn’t reveal how trash is affecting the species overall.
The more individuals and species are studied, the more reliable the numbers will become, she says.
Nevertheless, the current tally is a small fraction of what happens in the oceans, suggesting that many more animals are affected than we know.
But the takeaway, says Kühn, is quite clear. “Every species, regardless of location, habitat, or ecology, can potentially encounter and ingest or get entangled in plastic.”
“The results confirm our worst expectations,” says marine biologist Daniel Pauly, who leads the Seas Around Us initiative at the University of British Columbia. Despite animals having survived hunting and overfishing, Pauly says plastic waste could spell many marine creatures’ ultimate demise.
“I’m convinced that plastics will cause some species to go extinct and it breaks my heart just to think about that.”