The Great Pacific Garbage Patch is back in the news — the 3.5-million-ton swamp of plastic debris twice the size of Texas that prevailing winds have gathered in an out-of-the-way part of the Pacific Ocean north of Hawaii. The quickie version is at the San Francisco Chronicle; a readable and more thorough feature by Susan Casey can be found at Best Life. (Hat tip to Whet.)

The Chronicle story leans heavily on the idea that using canvas shopping bags instead of plastic will help. But it seems likely the problem is more insidious than that. The story claims that a recent Greenpeace report (“Plastic Debris in the World’s Oceans” PDF) “found that 80 percent of the oceans’ litter originated on land.” Bad journalism — actually, Greenpeace was more equivocal: “The United Nations Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP) estimated that land-based sources are responsible for up to 80% of marine debris,” citing a 2005 paper by Seba Sheavly of the Ocean Conservancy (PDF) — who’s actually citing a 1991 GESAMP report. The Garbage Patch has grown a lot since then, and even if it hadn’t, “up to 80%” can mean almost anything.

I lost the trail of references there because Sheavly’s paper never would finish uploading. Inexact figures poorly quoted doesn’t show there’s no problem — that non sequitur is the main tool of right-wing disinformation experts — but that the solution is going to have to be more drastic than declining one conspicuous use of plastic. Greenpeace’s useful list of citations includes a technical article from Marine Pollution Bulletin. In 1999 the authors actually collected and sorted samples from the Garbage Patch. Most of it was unidentifiable fragments, thin plastic film, and monofilament line.

But there’s worse news. It’s not just that more than 200 species of seabirds, marine mammals, fish, and turtles ingest plastic or are choked by it. As in the case of smog, the tiniest particles are the worst, as an article just published in Environmental Science & Technology (PDF) shows. From the American Chemical Society’s press release: “Researchers exposed several different types and sizes of microplastics to phenanthrene, a major marine pollutant, and used a model to predict their effects on a group of sediment-dwelling marine worms (lugworms). The scientists found that addition of just a few millionths of a gram of contaminated microplastics to the sediments caused an 80% increase in phenanthrene accumulation in the tissues of the worms. Since lugworms are at the base of the food chain, phenanthrene from microplastics would be passed on and biomagnified in other marine animals.

More research is needed, but meanwhile it’s not too early to start thinking what an economy would look like that required the full costs of plastic to be included in the price of grocery bags, computers, Saturns, and monofilament line.