Researchers have found 60 percent of the world's seabirds have plastic fragments in their stomachs and predict the figure will increase to 99 percent by 2050.
The study, conducted by scientists from Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) and Imperial College London, is published in the journal Proceedings of the National Academy of Sciences.
Lead researcher Chris Wilcox, from CSIRO Marine and Atmospheric Research, who is stationed in Hobart, in Tasmania, Australia, said seabirds, including albatrosses, shearwaters and penguins, ingest pieces of plastics, mistakenly thinking they are food.
In a phone interview from Paris, where Wilcox is participating in a United Nations working group on reducing land-based waste going into the oceans, he told Plastics News seabirds and turtles are surface feeders and swallow smaller polymer items that float.
Mistaking plastics for food
Seabirds are more likely to swallow rigid plastics; turtles “prefer flexibles found in the water column, like polyethylene film.” Wilcox said turtles probably mistake flexible plastics for jellyfish, which form part of their diet.
He said there is no preference in color or shape of plastics fragments, but items as large as toothbrushes, cigarette lighters and a doll's arm have been found in larger birds' stomachs.
“If something looks different, especially to predatory species, they probably think it may be better than their usual diet,” Wilcox said.
He said fish eggs sometimes adhere to plastic fragments, but scientists do not know whether birds eat them because they recognize the eggs as having nutritional value or just ingest the polymer item because it looks different.
Wilcox, a statistician who was educated at the University of California, Santa Cruz, and has worked in Australia for the last 10 years, said he and CSIRO colleague Denise Hardesty, a seabird biologist, developed the idea for the research. They asked Erik van Sebille, who was previously with Sydney-based University of New South Wales, and now at Grantham Institute, at Imperial College London, to collaborate.
The research involved assembling all the “seabird literature” published since the 1960s and analyzing it. The trio discovered plastic was present in fewer than 5 percent of seabirds in 1960, rising to 80 percent by 2010. They estimate the 2015 figure at nearly 60 percent but predict plastic ingestion will affect 99 percent of the world's seabird species by 2050, based on current trends.
A CSIRO statement said the plastic includes bags, bottle caps, and plastics fiber from synthetic clothes that have washed into the oceans from rivers, sewers and waste deposits. Swallowing plastic can cause gut impaction, weight loss and sometimes death for birds and turtles.
Wilcox told Plastics News the research study is part of a broader scientific program he has worked on since 2009. It examines sources for plastic that end up in oceans, wildlife impacts, relationships between public policy and debris going into oceans, and the distribution of plastic waste once it reaches the oceans.
His team has conducted a major research project around the Australian coastline, which will be published soon. He said there are statistical correlations between government policies and debris. Coast-based municipal councils that prosecute illegal dumpers experience “discernibly less debris” in the oceans.