Plastic Pollution harming seabird populations, not just individual birds
Plastic pollution is now being linked to changes in a wild seabird population, with new research showing that even small amounts of swallowed plastic can reduce the chances of young birds surviving to reproduce.
The study followed sable shearwaters from Lord Howe Island, a remote Australian breeding site, using 15 years of data. These seabirds spend several years at sea after leaving the colony before returning as adults to breed.
The findings show that plastic eaten during the chick stage can have consequences long after the birds leave the island. A chick consuming just 0.5 grams of plastic has a 12% lower chance of eventually returning to the colony to breed. Around one in five chicks consumes at least one gram.
At higher levels, the outlook becomes considerably worse. Birds that ingest more than two grams are unlikely to return to the breeding colony, while chicks fed more than five grams of plastic are likely to die at sea before reaching adulthood.
Sable shearwaters are particularly vulnerable because adult birds can mistake floating plastic for food and carry it back to their chicks. Previous research has linked plastic ingestion in these birds to serious physical damage, including a condition known as plasticosis.
The new study moves the issue beyond individual injuries and mortality. Because fewer young birds survive to become breeding adults, plastic ingestion can affect the ability of the wider colony to replace itself.
That matters because the Lord Howe population is already declining slowly. The birds’ long lifespans can mask the consequences of poor juvenile survival for years, meaning the full population impact of plastic pollution may take time to become visible.
Dr Alex Bond, Principal Curator of Birds at the Natural History Museum and a co-author of the research, said the findings demonstrate that plastic pollution can influence population change in wild animals.
The research paper, Ingested plastics reduce recruitment and survival of an Australian seabird, was published in Proceedings of the National Academy of Sciences.
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