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Balloons the Number 1 Marine Debris Risk of Seabird Mortality

A study by the Institute for Marine and Antarctic Studies (IMAS) and CSIRO has found that balloons are the highest-risk plastic debris item for seabirds – 32 times more likely to kill than the ingestion of hard plastics.

Researchers from IMAS, CSIRO and the Antarctic Climate & Ecosystems Cooperative Research Centre looked at the cause of death of 1733 seabirds from 51 species and found that one in three had ingested marine debris. The data showed that a seabird ingesting a single piece of plastic had a 20% chance of mortality, rising to 50% for nine items and 100% for 93 items.

The study, led by former IMAS-CSIRO PhD student Dr Lauren Roman and published in Scientific Reports (, found that although hard plastic accounts for the vast majority of debris ingested it is far less likely to kill than soft plastics such as balloons.

“Marine debris ingestion is now a globally recognised threat,” Roman said. “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. Although soft plastics accounted for just 5% of the items ingested they were responsible for more than 40% of the mortalities.

“Balloons or balloon fragments were the marine debris most likely to cause mortality, and they killed almost one-in-five of the seabirds that ingested them.

“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,” Roman said.

Although the study showed that soft items such as balloons are more dangerous, Roman added: “While hard plastics are less likely to kill than soft plastics they were still responsible for more than half of the seabird deaths identified in our study”.