Dear Straight Dope: I have been reading about this floating garbage island in the Pacific on various news sites for years now. It's always the same information and never any pictures. I've looked all over Google Earth for this island of debris that's supposed to be as large as Australia by some accounts and nada, nothing, bupkus. Reports say that it's growing exponentially due to typhoons, littering, and maritime accidents and that thousands of birds are dead or dying on the surface, strangled after gorging on plastic water bottles. This means that someone has actually seen it up close or has lied through their lying teeth. Now they're saying that there's an Atlantic floating island and it's as large as Iceland. Or Greenland. Or Australia. Are the liars lying through their lying teeth, or are there really floating garbage islands bumping into the land masses of the Atlantic and Pacific Oceans? Worried About the Birds

SDStaff paperbackwriter replies:

Such areas of plastic debris accumulation do exist — as Cecil confirmed a couple of years ago — and there are people who have seen them up close. The idea, however, that you could prove or disprove their accounts by looking at Google Earth images is half-baked at best. Google doesn’t provide high-resolution imagery for the middle of the ocean. And even if it did, you wouldn’t be able to see the tiny particles that make up the garbage patches.

Calling these garbage islands is highly misleading, as they’re not solid expanses of plastic you can walk on. The plastic collected in the confluence of ocean currents called the North Pacific Central Gyre, for example, is in the form of very, very small pieces, almost invisible to the naked eye. One study of the gyre found 334,271 pieces of plastic per square kilometer of ocean surface, but these pieces weighed only 5,114 grams altogether — that’s about 11 pounds. The average piece of plastic they found weighed only about 15 milligrams, or about the weight of a grass seed. The great majority of these particles are less than 2.8 millimeters in diameter, or a bit more than a tenth of an inch. Mostly they’re shreds of plastic film, as from garbage and shopping bags, and bits of monofilament fishing line and nets.

The idea of a garbage island also implies there is a distinct edge to the area where the plastic debris is found. This is another misconception. As you sail west from the Pacific coast of the U.S. the density of particles increases until you reach an area that is roughly between 135° W and 155° W and 35° N and 42° N – the center of the gyre. This is as substantial as the garbage patch gets, but to the naked eye, it’s just an expanse of relatively calm water that the major currents in the North Pacific circle around. Even here the average density of particles is only 11 pieces of plastic per cubic meter. The only way to see a garbage island is by dragging a plankton net through it.

You’re right to be worried about the birds, and marine life in general, though. Eighty-two of 144 maritime bird species sampled in one worldwide study had plastic debris in their stomachs. In 1985 one scientist estimated that plastic debris ingestion and entanglement (i.e., in fishing nets or longline fishing gear) kills 100,000 marine mammals each year in the North Pacific alone. In some areas inorganic fragments make up a greater proportion of the plankton layer (by mass) than organic material does. This is especially bad for filter feeders – a group that includes shrimp and small fish as well as the baleen whales – which are ingesting plastic instead of plankton.

SDStaff paperbackwriter, Straight Dope Science Advisory Board

Send questions to Cecil via cecil@straightdope.com.

STAFF REPORTS ARE WRITTEN BY THE STRAIGHT DOPE SCIENCE ADVISORY BOARD, CECIL'S ONLINE AUXILIARY. THOUGH THE SDSAB DOES ITS BEST, THESE COLUMNS ARE EDITED BY ED ZOTTI, NOT CECIL, SO ACCURACYWISE YOU'D BETTER KEEP YOUR FINGERS CROSSED.