90 percent of seabirds are eating plastic

Few people would be surprised to hear that there’s lots of plastic in the oceans, and that this is a bad thing. But while phenomena like the Pacific Garbage Patch, a dense accumulation of plastic and other debris in the subtropical North Pacific, are well known, the effect of ocean plastic on wildlife hasn’t been studied much at a global scale. And according to a comprehensive new study, plastic poses a risk to seabirds that is much more serious, and more widespread, than we have realized.

A team of Australian researchers modeled the distribution of plastic throughout the world’s oceans and compared these patterns with the ranges of 186 seabird species. They also combed the scientific literature for studies that looked for plastic ingestion by seabirds, which have identified plastic in the guts of 81 seabird species so far.

Both the number of seabird species in which plastic has been found and the percentage of individuals with plastic in their guts have increased over time, the researchers reported yesterday in the Proceedings of the National Academy of Sciences. Based on these trends they calculate that on average 90 percent of individual seabirds across all species likely contain plastic today.

Projecting this model into the future yields even starker statistics. By 2050, the researchers say, plastic is likely to be found in 95 percent of birds within 99.8 percent of all seabird species. That is, by mid-century nearly every individual seabird on the planet will have plastic in its body.

Eating plastic can harm seabirds by taking up space in the stomach, blocking the digestive tract, or exposing the birds to toxic chemicals. Plastic itself contains such chemicals, and it’s also frightfully good at grabbing onto toxins from the surrounding seawater and then releasing them once inside a warm-blooded creature’s body.

The impact of ocean plastic depends on the amount of debris in the water and the number of seabird species found in an area. This sounds like common sense, but actually it means that plastics are a bigger problem in more parts of the ocean than scientists have previously thought.

The researchers’ map of ingestion risk shows that seabirds are at greatest risk from ocean plastic in a band around the northern boundary of the Southern Ocean, particularly in the Tasman Sea between Australia and New Zealand and in the southwestern corner of the Indian Ocean.

In the past, scientists have considered the Southern Ocean to be relatively free from human influence, but the new analysis makes clear that so much plastic has been entering the ocean for so long that significant amounts of it have reached even these remote waters.

The Southern Ocean does not have as high a concentration of plastic as some other areas. But it is a hotspot of seabird diversity, and there is enough plastic there to make this form of pollution a serious concern.

More plastic in the ocean means more plastic ingestion by seabirds, and until now more plastic production by humans – the amount we make is doubling every 11 years – has meant more plastic in the ocean. This also sounds like common sense, but it doesn’t have to be this way.

The researchers note that their model could also calculate the effects on seabirds of waste management practices that reduce the amount of plastic entering the ocean, and mention that plastic ingestion by northern fulmars has decreased in recent years, presumably because manufacturers in northern Europe have been taking greater care not to spill so many plastic pellets into the water. This, once again, sounds like common sense, but in this case there is no “but.” – Sarah DeWeerdt | 1 September 2015

Source: Wilcox C. et al. “Threat of plastic pollution to seabirds is global, pervasive, and increasing.” Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1502108112

Header image: Cape petrels (Daption capense) photographed near Antarctica. The species is widely distributed throughout the Southern Ocean, an area of high seabird diversity and high risk from plastic pollution. Credit: Liam Quinn via Flickr.

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