Plastic trash isn't just accumulating in oceans around the planet. It's also increasingly piling up somewhere even more vulnerable: inside the stomachs of seabirds, from albatrosses to penguins, that confuse the indigestible garbage with food.
In 1960, fewer than 5 percent of individual seabirds had evidence of plastic in their stomachs. That soared to 80 percent in 2010, and now it's up to 90 percent.
This is according to a new study, led by researchers from Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO), that analyzes the risk based on distribution patterns of marine debris, the ranges of 186 seabird species, and studies of birds' plastic ingestion conducted between 1962 and 2012.
Not only does the study suggest 90 percent of all seabirds alive today have eaten plastic of some kind, but based on current trends, it predicts 99 percent of seabird species on Earth will be plagued by plastic ingestion within 35 years.
"For the first time, we have a global prediction of how wide-reaching plastic impacts may be on marine species — and the results are striking," lead author and CSIRO scientist Chris Wilcox says in a press release. "We predict, using historical observations, that 90 per cent of individual seabirds have eaten plastic. This is a huge amount and really points to the ubiquity of plastic pollution."
Floating pieces of plastic resemble food to soaring seabirds like this wandering albatross. (Photo: Ben/Flickr)
The plastic being eaten by seabirds runs the gamut from bags, bottle caps and cigarette lighters to plastic fibers from synthetic clothes, the researchers say, much of which ends up at sea after washing through urban rivers, sewers and waste deposits.
But why are seabirds eating it? Since they rarely have time to examine their seafood before it gets away, many seabirds have evolved to rapidly grab meals from the water as they fly or swim by. This eat-first-and-ask-questions-later strategy had few risks for most of their history, but the past 60 years have brought a sea change to Earth's oceans by peppering them with specks of stomach-clogging plastic.
The problem is especially evident among Laysan albatrosses, which hunt by skimming the surface with their large beaks. They end up eating lots of plastic this way, some of which they later regurgitate for their chicks on land. But while adults can throw up inedible trash they've accidentally eaten, their chicks can't. Depending on the debris, too much might tear a chick's stomach or just cause it to starve despite feeling full. Evidence of such misfortune has become surprisingly common in some places, documented in heartbreaking photos like this one from Midway Atoll:
This albatross chick's parents unwittingly fed it a fatal diet of plastic debris in 2009. (Photo: Chris Jordan/USFWS)
Bottle caps and cigarette lighters are among the debris often found in seabird stomachs. (Photo: Trevor Leyenhorst/Flickr)
Although plastic pollution affects seabirds worldwide, the researchers say it has the most devastating impact in places with high biodiversity. And according to their study, ocean plastic's worst effects occur in the Southern Ocean, specifically a band around the southern edges of Australia, South Africa and South America.
"We are very concerned about species such as penguins and giant albatrosses, which live in these areas," says co-author Erik van Sebille, an oceanographer at Imperial College London. "While the infamous garbage patches in the middle of the oceans have strikingly high densities of plastic, very few animals live [there]."
This research helps illuminate another recent study, which reported that Earth's monitored seabird populations have fallen by 70 percent since the 1950s — the equivalent of about 230 million birds in just 60 years. As the authors of that study explained in a statement, this isn't just a problem for seabirds, since the winged predators are like canaries in a coal mine for their entire ecosystem.
"Seabirds are particularly good indicators of the health of marine ecosystems," said Michelle Paleczny, a researcher at the University of British Columbia. "When we see this magnitude of seabird decline, we can see there is something wrong with marine ecosystems. It gives us an idea of the overall impact we're having."
An adult Laysan albatross rests at sunset on Midway Atoll. (Photo: Brenda Zaun/USFWS)
Fortunately, that impact may still be reversible. While plastic doesn't truly break down as biodegradable substance do, and removing it from the sea is generally impractical, recent research suggests it doesn't linger in surface waters for long.
An estimated 8 million metric tons of plastic now enters the oceans every year, fueled by explosive growth of commercial plastic production — an output that has roughly doubled every 11 years since the 1950s. Just by reining in that flood of plastic, researchers say we might be able to slow the global decline of seabirds.
"Improving waste management can reduce the threat plastic is posing to marine wildlife," says CSIRO researcher Denise Hardesty, a co-author of the new study. "Even simple measures can make a difference, such as reducing packaging, banning single-use plastic items or charging an extra fee to use them, and introducing deposits for recyclable items like drink containers."