How bad is the ocean's plastic problem? What sea birds tell us.

Nearly 90 percent of all seabirds alive today have plastic in their stomachs – including remnants of bags, bottle caps, and plastic fibers from synthetic clothes, which have washed out into the ocean from urban rivers, sewers and waste deposits – scientists estimate.

The researchers from Australia's the Commonwealth Scientific and Industrial Research Organisation and Imperial College London looked at published studies since the early 1960s, and found that the number of seabirds – including albatrosses, shearwaters, and penguins – that have ingested plastic has increased significantly since 1980.

In 1960, less than five percent of seabirds had plastic in their stomachs; they put that number at 90 percent today.

"We predict, using historical observations, that 90 percent of individual seabirds have eaten plastic. This is a huge amount and really points to the ubiquity of plastic pollution,” said Dr. Chris Wilcox, study leader and senior research scientist at CSIRO Oceans and Atmosphere in a news release.

Birds ingest the material at such high rates because they often confuse the brightly colored items floating on surface waters with food and “this causes gut impaction, weight loss, and sometimes even death,”  the researchers said.

According to the study, that figure is set to increase. Last December, research found that, more than 5 trillion pieces of plastic, weighing nearly 269,000 tons, are littering the world's oceans.

The study, which was published Tuesday in the Proceedings of the National Academy of Sciences, indicates that plastics will have the greatest impact where most seabirds are found, which is in the Southern Ocean, near Australia, South Africa, and South America.

But simple measures could curb the trend, such as finding ways to reduce plastic waste getting into the oceans, the researchers say.

"Because exposure to plastic turns out to be a strong predictor of how much plastic the birds have in them; that is, the more plastic they're exposed to, the more they ingest – this implies that if we reduce the amount of plastic going into the oceans, you would expect all these species to essentially respond,” Dr. Wilcox explained to BBC.

"And this makes this problem different from something like climate change. It ought to be relatively easy to fix."

Jenna Jambeck from the University of Georgia, an expert on plastic waste issues notes the link between basic waste management practices on land and the impacts being felt by seabirds.

"It illustrates that if we implement solutions to reduce plastic input into the oceans, we can reduce impacts to individual seabirds," Professor Jambeck told the BBC.

"Solutions include improving solid waste management where it is lacking, and also working upstream on product redesign and materials substitution moving towards a more circular system," Jambeck said.