July 4 () –
A monitoring of 77 species of petrels has revealed that a quarter of all the plastics they can find in their search for food They are found in remote international waters.
The authors of the study conclude that international collaboration is required to solve this problem, they warn in the journal ‘Nature Communications’.
The extensive study assessed the movements of 7,137 individuals of 77 petrel species, a broad-spectrum group of migratory seabirds that includes the critically endangered northern fulmar, storm petrel and Newell’s shearwater.
It is the first time that monitoring data from so many species of seabirds and overlay world maps of ocean plastic distribution.
The results show that plastic pollution threatens marine life on a scale that transcends national borders: a quarter of all plastic exposure risk occurs on the high seas. This is largely related to oceanic gyres — large systems of rotating ocean currents — where huge accumulations of plastics, fed by waste entering the sea from ships and from many different countries.
Seabirds often mistake small pieces of plastic for food, or ingest plastic that has already been eaten by their prey. This can lead to injury, poisoning and starvation, and petrels are especially vulnerable because they cannot easily regurgitate plastic.
In the breeding season, they often inadvertently feed their chicks plastic. Plastics can also contain toxic chemicals harmful to seabirds.
Petrels are a poorly studied but vulnerable group of marine species that play a key role in oceanic food webs. The extent of its distribution throughout the ocean makes them important “sentinel species” when assessing the risks of plastic pollution in the marine environment.
“Ocean currents cause large eddies of plastic garbage to accumulate far from land, out of sight and beyond the jurisdiction of any country. We have found that many species of petrels spend a lot of time feeding around these ocean gyres, which that puts them at high risk of ingesting plastic debris,” explains Lizzie Pearmain, a PhD student in the Department of Zoology at the University of Cambridge (UK) and British Antarctic Survey, and a co-author of the study.
“When petrels eat plastic, it can get stuck in their stomachs and feed their chicks,” he explains. This leaves less room for food and can cause internal injuries or release toxins.”
Petrels and other species are already threatened with extinction due to climate change, bycatch, competition with fisheries, and invasive species such as mice and rats in their breeding colonies. The researchers claim that exposure to plastics may reduce the resistance of birds to these other threats.
The northeastern Pacific, south Atlantic, and southwestern Indian oceans have ocean gyres littered with plastic debris, where many species of threatened seabirds feed.
“Even species at low risk of exposure have been found to eat plastic. This shows that plastic levels in the ocean are a problem for seabirds around the world, even outside of these high-exposure areas,” adds Dr. Bethany Clark, BirdLife International Seabird Science Officer and co-author of the study.
“Many species of petrels are at risk of being exposed to plastic in the waters of various countries and on the high seas during their migrations,” he continues. “Due to ocean currents, this plastic debris often ends up far from its original source. This puts highlights the need for international cooperation to tackle plastic pollution in the world’s oceans”.
The study also found that the Mediterranean Sea and the Black Sea together account for more than half of the global plastic exposure risk for petrels. However, only four species of petrels feed in these closed and crowded areas.
The study was led by a partnership between the University of Cambridge, BirdLife International and the British Antarctic Survey, in collaboration with Fauna & Flora International, the 5 Gyres Institute and more than 200 seabird researchers from 27 countries.
To obtain their results, the researchers overlaid global location data, taken from tracking devices attached to birds, to pre-existing maps of distribution of marine plastics. This allowed them to identify bird migration and feeding areas where they are most likely to encounter plastics.
The species received a “exposure risk score” to indicate your risk of encountering plastic during your stay at sea. Several already threatened species scored highly, including the critically endangered Balearic shearwater, which breeds in the Mediterranean, and the Newell’s shearwater, endemic to Hawaii.
Another endangered species, the Hawaiian petrel, also scored high for plastic exposure risk, as did three species classified by the IUCN as vulnerable: the Yelkouan shearwater, which breeds in the Mediterranean; the Cook’s petrel, which breeds in New Zealand, and the spectacled petrel, which breeds only on an extinct volcano called Inaccessible Island, part of the Tristan da Cunha archipelago, a British Overseas Territory.
“Although the population-level effects of plastic exposure for most species are not yet known, many petrels and other marine life are already in a precarious situation. Continued exposure to potentially hazardous plastics adds to the pressures,” says Professor Andrea Manica, from the Department of Zoology at the University of Cambridge and co-author of the study.
“This study is a big step forward in understanding the situation, and our results will inform conservation efforts to try to address the threats to seabirds,” he concludes.
