Threatened seabirds are spending days and sometimes weeks foraging for food around floating garbage patches in the ocean, according to a major study that warns international action to tackle plastic pollution is urgently needed.
The research used tracking data from more than 7000 birds, combined with plastic pollution location data, to map the plastic exposure risk of 77 species of petrel, a group of migratory seabirds.
It found that 25 per cent of all plastic exposure for seabirds occurs outside national jurisdictions, mainly at huge floating patches of pollution such as the Great Pacific Garbage Patch.
Birds can spend anywhere from hours to weeks foraging for food in these pollution hotspots, says team member Bethany Clark at the charity BirdLife International.
“During the breeding season, they spend less time [at pollution hotspots] because they have to get back to feed their chicks. But that can still be many hours, and then in the non-breeding season, they can spend weeks,” she says.
Previous studies have found that plastic can get caught up in seabirds’ stomachs, causing obstructions and poisoning. Petrels have also been shown to regurgitate plastic pollution to feed to their chicks.
Worryingly, some of the most threatened birds, such as shearwaters and Hawaiian petrels, are among the species with the most exposure to ocean plastic.
“It’s concerning for us that some of these really threatened species are also suffering from having to feed in areas with lots of plastic,” says Clark.
Given that a large proportion of plastic exposure takes place beyond national jurisdictions, Clark is calling for countries to work together on global solutions to tackle the sources of pollution.
Cracking down on plastic waste from fishing vessels and reducing the use of single-use plastics would be effective first steps, she says.
Countries are also working under the United Nations process to draw up a global, legally binding treaty to curb plastic pollution, which could come into force from 2025.
The study only considered the exposure risk experienced by the birds, rather than assessing how much plastic was actually ingested by different populations and species.
That is an area for future research, says team member Lizzie Pearmain at the University of Cambridge. “For future studies, if we find that two different populations have more or less plastic ingestion than expected just from the spatial overlap, then we can start to understand whether they are actively avoiding it, or more likely to ingest it,” she says.