Plastic waste sickens and weakens foraging seabirds

Photos of seabirds with their necks and legs hopelessly entangled in plastic waste have become commonplace online in a testament to the devastating impacts of plastic pollution.

So have images of the plastic contents in the stomachs of dead birds that succumbed after ingesting plastic objects by mistaking them for food.

A study published in March confirmed that these incidents, rather than being isolated, indicate an alarming trend. “Using cause of death data from 1,733 seabirds of 51 species, we demonstrate a significant relationship between ingested debris and a debris-ingestion cause of death (dose-response),” its authors explain.

“There is a 20.4% chance of lifetime mortality from ingesting a single debris item, rising to 100% after consuming 93 items,” they elucidate. “Obstruction of the gastro-intestinal tract is the leading cause of death. Overall, balloons are the highest-risk debris item; 32 times more likely to result in death than ingesting hard plastic.”

Now a new study paints an equally troubling picture. Even when seabirds do survive after ingesting plastic bits, they often end up suffering a variety of severe health problems as a result, its authors say.

The researchers, who work at the University of Tasmania, discovered this after analyzing blood samples from flesh-footed shearwaters on Lord Howe Island in Australia. They found that many of birds had several severe health conditions, including high levels of cholesterol. They also grow to be considerably smaller and weaker than specimens on a normal diet.

“Flesh-footed Shearwaters populations are declining across the south west Pacific Ocean and Western Australia’s south coast,” explains Dr. Jennifer Lavers, a marine eco-toxicologist who led the study. “Our study found that birds which ingested plastic had reduced blood calcium levels, body mass, wing length, and head and bill length.”

In addition, the birds’ kidney function was likewise impaired with a higher concentration of uric acid. “Our data did not show a significant relationship between the volume of plastic ingested and the health of individuals, suggesting that any plastic ingestion is sufficient to have an impact,” the scientist elucidates.

“Until now there has been scant information on the blood composition of seabirds in the wild, many of which have been identified as threatened species,” she says. The fear, she adds, is that sickened seabirds will face much higher mortality rates, which could be a further threat to species already facing various challenges from habitat loss to climate change.