Balloons the biggest risk to seabirds
Soft plastics mistaken as food cause fatal obstructions, research shows. Nick Carne reports.
Balloons are 32 times more likely to kill seabirds than hard plastics, Australian research shows.
A study of 1733 seabirds from 51 species found that while balloons and other soft plastics accounted for only 5% of plastics ingested, they were responsible for more than 40% of mortalities.
And one in three of the 1733 had ingested some form of marine debris.
“As similar research into plastic ingestion by sea turtles has found, it appears that while hard plastic fragments may pass quickly through the gut, soft plastics are more likely to become compacted and cause fatal obstructions,” says research leader Lauren Roman.
The collaborative study was led by Australia’s Institute for Marine and Antarctic Studies (IMAS), with input from the CSIRO and the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC).
The findings are reported in a paper in the journal Scientific Reports.
Data analysis shows that a seabird ingesting a single piece of plastic has a 20% chance of mortality, but this rises to 50% for nine items and 100% for 93 items.
“Marine debris ingestion is now a globally recognised threat,” Roman says. “However, the relationship between the amount or type of debris that a seabird ingests and mortality remains poorly understood.
“Among the birds we studied the leading cause of death was blockage of the gastrointestinal tract, followed by infections or other complications caused by gastrointestinal obstructions.”
Co-author Chris Wilcox says the approach taken was developed for turtles before being applied to seabirds.
“These two applications are the first time there has been a robust estimate of the impact of plastic ingestion on free living marine species,” he said. “This is a critical step in triggering action to address plastic pollution.”
Seabirds, the authors note, are the world’s most threatened birds, with nearly half of all species experiencing population declines and 28% threatened globally.
Half of the world’s seabird species ingest marine debris, with the greatest expected adverse effects occurring in Australasia, at the Southern Ocean boundary of the Tasman Sea, where the highest global seabird biodiversity occurs.
Procellariiformes, including albatrosses and petrels, are particularly at risk as they mistake floating debris for food.
“All balloons in this study were ingested by species that eat squid, suggesting these squid-feeding species are likely to have higher mortality rates,” the researchers note in their paper.
“We suggest that reducing the presence of balloons and balloon fragments in the ocean would directly reduce seabird mortalities resulting from marine debris ingestion, and would have eliminated the 23% of confirmed KD [marine debris ingestion] deaths in this study for which balloons were cause.”