By Peter Fimrite
The giant mass of floating plastic that has imperiled birds and wildlife between San Francisco and Hawaii contains 1.8 trillion pieces of trash covering an area nearly four times the size of California — significantly bigger than previously thought — and it is growing, a study published Thursday concluded.
A team of scientists from the Ocean Cleanup Foundation, based in the Netherlands, said the debris field, known as the Great Pacific Garbage Patch, covers about 618,000 square miles of deep ocean and weighs 80,000 metric tons.
It is the largest accumulation of ocean plastics on Earth, and a serious threat to both marine animals and people, according to the three-year mapping study published Thursday in the journal Scientific Reports. That’s because eating plastic, which contains several harmful chemicals, can be toxic, so the birds and fish that eat it and the humans who in turn eat them can suffer health problems.
It is a particularly difficult problem to stop because the discarded plastic collects algae that smells to birds like seafood, according to a 2016 UC Davis study. Other studies have shown that as many as 90 percent of seabirds have plastic in their guts.
“It is important to quantify it, to understand it and to monitor it to see how it has moved over time,” said Laurent Lebreton, a French scientist and lead author of the study, which he contends is the most comprehensive analysis ever done of the garbage patch. “Marine life is eating that, so all of this is going up the food chain … and ending up on our plates in some aspect.”
The amount of detritus found — which also includes chemical sludge, fishing nets and other floating rubbish — was four to 16 times greater than shown in the two previous studies, which estimated the quantity of debris using different methods of measurement.
Taken together, the debris in the North Pacific would weigh as much as 500 jumbo jets. And if all of those floating bits of trash were divvied up, they would provide every human on the planet with 243 variously shaped chunks of junk, Lebreton’s study said.
The plastic ranges in size from large buoys to bottle caps to microscopic particles, and it is trapped in the upper water column — meaning near the surface of the ocean — by the swirling currents known as the North Pacific Gyre, where fish, whales, sea turtles and sea birds feed.
Conservationists have long worried about microplastics, the tiny bits that have been found in the stomachs of seabirds, including many petrels, auklets and gulls that live along the California coast.
But the researchers at Ocean Cleanup found that, although there are billions of pieces of plastic in the Pacific patch, 92 percent of its mass consists of larger objects. Those heavier pieces should be removed before they break down, scientists said.
“We were surprised by the amount of large plastic objects we encountered,”said Julia Reisser, an expedition scientist. “We used to think most of the debris consists of small fragments, but this new analysis shines a new light on the scope of the debris.”
The new study is based on two exploratory expeditions.
The first was in 2015, when a 30-boat armada used booms and 652 fine mesh nets to scoop out 1.2 million samples of plastic, which were classified and analyzed by lab technicians over the next two years. The second happened in 2016, when a C-130 Hercules aircraft out of Moffett Field took 3-D scans of the patch using infrared and high-resolution cameras and a laser sensor known as lidar.
Analysis of the debris field and surrounding water during the 2015 boat voyage, which stretched for 30 days, found a steady inflow of plastic into the patch. Researchers said that will continue to grow exponentially unless drastic measures are taken to reduce the proliferation of plastic garbage and litter back on land, and to prevent it from flowing out storm drains into waterways that lead to the ocean.
The huge sprawl of junk is particularly vexing to environmentalists in San Francisco and other eco-friendly population centers in California, where much of the debris probably originated. Mariners also don’t like it because the debris can foul up ship propellers.
In an effort to attack the problem, scientists with the Ocean Cleanup program have designed a floating 2,000-foot-long crescent-shaped barrier that uses a hollow plastic scoop jutting several feet under water to capture bits of plastic. The barrier, which slowly collects the debris as it drifts, is being assembled at the former Alameda Naval Air Station.
It is expected to be ready for a trial in a couple of months, officials said.
“These results provide us with key data to develop and test our cleanup technology, but it also underlines the urgency of dealing with the plastic pollution problem,” said Boyan Slat, the founder of Ocean Cleanup and co-author of the study. “Since the results indicate that the amount of hazardous microplastics is set to increase more than tenfold if left to fragment, the time to start is now.”
Peter Fimrite is a San Francisco Chronicle staff writer. Email:Twitter: pfimrite
“Marine life is eating that, so all of this is going up the food chain … and ending up on our plates.”
Laurent Lebreton, study’s lead author