Giant Plastic Island: Fact or Fiction?
Have you heard of the giant plastic island in the Pacific Ocean? Several times in casual conversation, I've been told that mankind is ruining the oceans to such an extent that there are now entire islands of plastic waste. Daily Kos tells us that this "island" is twice the size of Texas!
This struck me as incredible, in the most literal sense of the word, so I decided to look into the claim.
First, we can do a quick feasibility calculation. The mass of polyethylene terephthalate (PET), the plastic from which most water bottles are made, required to create a two-Texas-sized island just one foot thick is 9 trillion pounds. That's 15 times more than the world's annual production of plastic. Even if a year's worth of the world's spent plastic bottles could be airlifted out over the ocean and directly dropped in one spot, this island could not be made.
That's a rough calculation, so I decided to look more into peer-reviewed research on plastic accumulation in the oceans. The global network of ocean currents will sweep up floating debris and push it towards certain locations. Around the earth, this debris accumulates in regions called gyres, where a current vortex will tend to push suspended matter into a central area and trap it. There are major gyres in the North and South Atlantic and Pacific and the Indian Ocean.
Outside of those five major gyre regions, plastic density is very low and sometimes effectively zero when measured.
Scientific studies measure the amount of plastic present in the gyres by trawling through with enormous nets. The method is painstaking and subject to variation due to differences in mesh sizes of nets, trawling speed of the boat, the diligence of the measuring researchers and other variables.
A well-known 2001 study measured the density of plastic debris in the world's largest gyre, in the North Pacific. They found roughly 5 kg of plastic per square kilometer. This abstract figure is easier to handle when you break it down into a more fathomable number. In an area the size of an Olympic regulation swimming pool, this amounts to roughly two bottle caps' worth of plastic.
A 2013 study conducted in the South Pacific gyre found that plastic density there was 100 times lower than the North Pacific. That's one plastic bottle cap in roughly 50 Olympic pools.
This bottle cap analogy is not entirely correct either. Most of the plastic is actually broken down into microscopic bits or films suspended in the seawater at varying depths. They are mostly invisible to the naked eye. It's like you took the bottle caps and ground them into particles finer than sand.
So, here are the facts. Much of the ocean contains little to no plastic at all. In the smaller ocean gyres, there is roughly one bottle cap of plastic per 50 Olympic swimming pools' worth of water. In the worst spot on earth, there is about two plastic caps' worth of plastic per swimming pool of ocean. The majority of the plastic is ground into tiny grains or small thin films, interspersed with occasional fishing debris such as monofilament line or netting. Nothing remotely like a large island exists.
Clearly, the scale and magnitude of this problem is vastly exaggerated by environmental groups and media reports. Some researchers in the field agree, explicitly pointing out that these scare-stories "undermine the credibility of scientists."