There’s so much plastic floating in some parts of the ocean, especially in five large swirls known as “garbage patches,” that each square kilometer of surface water there holds almost 600,000 pieces of debris. The often bite-sized trash can harm birds and other marine life—even those that don’t go anywhere near today’s “garbage patches,” according to a new study. Indeed, because of the proliferation of floating trash by 2050, birds of almost every ocean-foraging species may be eating plastic.
The global production of plastic has doubled every 11 years or so since the 1950s. Only a small percentage ends up in the ocean, but that still adds up to about 300,000 tons per year at current production rates. Once floating at sea, the debris breaks up into ever smaller bits, says Chris Wilcox, a marine ecologist at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Hobart, Australia. More than 80 seabird species consume the often brightly colored bits, and as time goes on, more birds are eating more plastic. Wilcox and his colleagues estimate that in 2014, about 90% of individuals within these 80 species were consuming plastic.
That tally will only grow as other kinds of birds join the feast, the team reports in its new analysis of 186 oceangoing species from 42 genera (major groups of species) including albatrosses, gull, petrels, and penguins. In their study, Wilcox and his colleagues considered what the birds typically ate as well as where they are known to forage at sea. They analyzed this in combination with known concentrations of floating plastic, the growing rate of plastic production, and the growing number of bird species known to have eaten plastic (a number that’s increasing about 0.2% each year, Wilcox notes).
By 2050, about 99.8% of the species studied will have eaten plastic, the researchers report online today in the Proceedings of the National Academy of Sciences. Consuming plastic can cause myriad problems, Wilcox says. For example, some types of plastics absorb and concentrate environmental pollutants, he notes. After ingestion, those chemicals can be released into the birds’ digestive tracts, along with chemicals in the plastics that keep them soft and pliable. But plastic bits aren’t always pliable enough to get through a gull’s gut. Most birds have trouble passing large bits of plastic, and they build up in the stomach, sometimes taking up so much room that the birds can’t consume enough food to stay healthy.
A 2012 study published by the United Nations Convention on Biological Diversity shows that birds aren’t the only victims: More than 600 species from microorganisms to whales are affected by plastic waste in the oceans, mainly by ingestion but sometimes by getting tangled in larger debris like old fishing nets.
And even areas now fairly clear of plastic debris may become hazardous to the birds as concentrations of plastic debris continue to rise, the researchers suggest.
The team’s findings “bridge current gaps in data and illustrate geographic hotspots” where plastics may pose a problem in the future, says Richard Thompson, a marine biologist at Plymouth University in the United Kingdom. The research is unique in that it attempts to assess the problem worldwide rather than on a region-by-region and species-by-species basis, he notes.
The computer models and analytical techniques used by the team may appear to be too simplified, however, cautions Nikolai Maximenko, an oceanographer at the University of Hawaii's International Pacific Research Center in Honolulu. Nevertheless, he notes, “this is an important example of an effort to characterize the impact of marine debris on the ecosystem.”
Increased intake of pollutants is just one result of birds consuming trash, Thompson says. “We don’t fully understand all of the physical effects of ingesting plastic, but it’s hard to imagine that the effects are going to be positive.”