Petrels are a group of migratory seabirds that play an important role in oceanic food chains. However, scientists have already warned of the possible extinction of many petrel species due to climate change, bycatch and other threats. Now we know that plastic pollution is also a serious threat to these birds.
A team of researchers from Cambridge University has found that plastic litter poses a health risk to petrels and can exacerbate other threats they already face. Because of their distribution in the world’s oceans, these birds are important “indicator species” in assessing the risks of plastic pollution in marine ecosystems.
The study used global tracking data to identify where petrels are most likely to encounter plastic during their migrations and food searches. Each species was assigned an “exposure risk score” indicating the likelihood of encountering plastic debris.
Analysis of the data showed that plastic pollution threatens marine life not only near shore, but also offshore. One-quarter of all plastic impacts occur on the high seas. This is due to the presence of gyres – systems of rotating ocean currents, where huge accumulations of plastic, fed by waste from various countries and boats, are formed.
Seabirds, including petrels, often mistake small pieces of plastic for food or swallow them along with their prey. This can lead to injury, poisoning and starvation. Petrels are particularly vulnerable to the toxic substances in plastic during the breeding season, as they inadvertently feed their chicks with plastic.
“We have found that many petrel species spend a lot of time near mid-ocean cycles where plastic debris accumulates. This puts them at high risk of ingesting plastic,” said Lizzie Pearmein, one of the study’s co-authors.
The hotspots of plastic pollution that host large numbers of endangered petrels are in the northeast Pacific, South Atlantic and southwestern Indian Ocean. Mid-ocean cycles filled with plastic waste form in these areas.