A boy collects plastic materials near a polluted coastline to sell in Manila, April 9, 2008. Reuters/Cheryl Ravelo

In his book “The World Without Us,” American journalist Alan Weisman describes the Great Pacific Garbage Patch as “a sump where nearly everything that blows into the water from half the Pacific Rim eventually ends up.” This region of spinning debris — most of which, quite unsurprisingly, is plastic — is located in the Northern Pacific Ocean, stretching from the West Coast of North America to Japan.

The exact size of this wind-driven, swirling gyre of flotsam is hard to glean, with estimates ranging from 0.4 percent of the size of the Pacific to a staggering 8 percent of the ocean. However, as the U.S. National Oceanic Atmospheric Administration explains, the use of the word “patch” to describe the region can be a bit misleading — conjuring images of a large and clearly visible island of litter.

“While higher concentrations of litter items can be found in this area, along with other debris such as derelict fishing nets, much of the debris is actually small pieces of floating plastic that are not immediately evident to the naked eye,” the NOAA says.

The Great Pacific Garbage Patch — a wind-driven, swirling gyre of flotsam in the Northern Pacific Ocean. NOAA

Now, the first-ever aerial survey of the region has revealed that the density of rubbish in the heart of the garbage patch is far worse than previously believed. The survey, carried out by the Ocean Cleanup — an organization that is partly funded by the Dutch government — also threw up a disturbing find — a large chunk of the trash in the region is now composed of visible garbage such as fishing nets and plastic containers, suggesting that the concentration of large debris may have been “heavily underestimated.”

“This first-ever aerial survey of floating ocean plastic provided confirmation of the abundance of plastic debris sized 0.5 metre and up. While the flight plan took us along the Northern boundary of the patch, more debris was recorded than what is expected to be found in the heart of the accumulation zone,” the Ocean Cleanup said in a statement. “Initial estimates of the experienced observer crew indicate that in a span of 2.5 hours, over a thousand items were counted.”

According to a 2014 estimate, more than five trillion pieces of plastic — collectively weighing nearly 270,000 tons — are currently floating in the world’s oceans. The problem is plastic does not decompose the same way organic material does. Instead, it breaks down into ever smaller “nurdles” — microplastics that are then ingested by zooplanktons living in oceans, and eventually by fish and humans.

Even large pieces of plastic, before they can break down into smaller fragments, pose a serious threat to marine life, with “ghost nets” — discarded fishing nets usually made of nylon and polyethylene — ensnaring sea life and ship propellers.

“The Aerial Expedition - our final reconnaissance mission - brings us another step closer to the cleanup of the Great Pacific Garbage Patch,” Boyan Slat, CEO and founder of the Ocean Cleanup, said in the statement. “The initial findings of the expeditions again underline the urgency to tackle the growing accumulation of plastic in the world’s oceans.”