Plastic waste in oceans is causing $13 billion of damage each year, according to the UNEP report, and that figure could be much higher. Worldwide plastic production is projected to reach 33 billion tons by 2050, and plastic makes up 80% of litter on oceans and shorelines.
"Plastics undoubtedly play a crucial role in modern life, but the environmental impacts of the way we use them cannot be ignored," said UNEP Executive Director Achim Steiner in a press release.
Ten to 20 million tons of plastic end up in the ocean each year, from litter, runoff from poorly managed landfills, and other sources. Once it's in the water, plastic does not degrade but instead breaks into smaller pieces and swirls in massive ocean gyres, creating soupy surfaces peppered with the material
Scientists are especially worried about the growing prevalence of tiny microplastics which are smaller than 5 millimeters. These include microbeads, which are used in toothpaste, gels, facial cleansers and other consumer goods. Microplastics aren't filtered by sewage treatment plants, and can be ingested by marine animals with deadly effect.
It's expensive and ineffective to clean up existing marine debris. Picking trash off beaches or sweeping it from the ocean surface "does nothing to fix the problem at the source," said Doug Woodring, the co-founder of Ocean Recovery Alliance, the NGO behind the Plastic Disclosure Project.
"It's not just an ocean problem, it's a business and a municipal issue," Woodring said. "The ocean is just downstream of our activities. The real solution is upstream at the producer and user end."
Governments can help solve the problem by regulating the use of plastics and creating infrastructure to recycle them. For example, dozens of nations have banned plastic bags at supermarkets or restricted their use.
That's a "good start," said Ada Kong, a campaigner at Greenpeace. But they can go further, she said. "Governments should enforce laws to regulate the cosmetic manufactures to label the ingredients (of consumer goods), including all the microplastics."
The general public can also be conscious about their plastic footprint by simply purchasing goods without a lot of excess plastic packaging. People should also separate their plastic from other waste and recycle it, Woodring said.
From waste to resource
Companies that produce plastic goods have perhaps the biggest opportunity to make a difference, Woodring said. They can engage their customers with rebate or deposit programs, giving them incentives to bring back plastic for recycling.
"Everything from bottles to food packaging can be made from recycled plastic," Woodring said. "The technology is there today to reuse it."
His organization is hosting a "Plasticity Forum" in New York City on Tuesday featuring presentations about how to creatively reuse plastic.
Plastic isn't just waste -- it's "a valuable material, pound-for-pound worth more than steel, and we're just not capitalizing on it today," Woodring said.
The new reports come on the eve of the first-ever United Nations Environment Assembly in Nairobi, a forum for environmental ministers, scientists, and others to discuss strategies to combat climate change and other environmental problems. An ocean conference hosted by U.S. Secretary of State John Kerry in Washington, D.C. last week also focused on marine pollution.
Perhaps the greatest sign of the problem is the rapidly-growing Great Pacific Trash Patch, a massive sheet plastic and other debris that circles in a gyre across the ocean.