Thursday, March 21, 2013

The Great Pacific Garbage Patch

How plastic is changing the ecosystem of the North Pacific Gyre

You’ve probably heard of the Great Pacific Garbage Island – a floating island of solid plastic and trash, somewhere out in the North Pacific.  Well, it doesn’t exist, at least not in the form that seems to have pervaded popular culture.

In the North Pacific Ocean, the northern jet stream and the opposite-moving southern trade winds create an oceanic gyre.  In the centre is a large area of relatively stationary water, while the steadily turning currents surrounding it create a flow much like a whirlpool.  This flow gathers floating garbage and debris, which builds up in the centre as it cannot escape the vortex once it enters it. This phenomenon, together with the world’s increasing reliance on, use, and (inappropriate) disposal of plastics, has created the so-called Great Pacific Garbage Patch.

It was predicted in 1988 in a scientific publication, and observed first-hand in 1997 by oceanographer and racing boat captain Charles J. Moore.  He was returning to California from a yachting race in Hawaii, when he encountered the floating trash:
Yet as I gazed from the deck at the surface of what ought to have been a pristine ocean, I was confronted, as far as the eye could see, with the sight of plastic.  It seemed unbelievable, but I never found a clear spot. In the week it took to cross the subtropical high, no matter what time of day I looked, plastic debris was floating everywhere: bottles, bottle caps, wrappers, fragments. 
The disturbing image these eloquent words portrayed attracted significant attention from the media, and variants on “the Great Pacific Garbage Island” have appeared in countless newspapers and magazines.  Unfortunately at some point – whether accidentally or on purpose to make the story more shocking – a picture of highly polluted Manila harbour was mislabelled as the Great Pacific Garbage Island.

NOT the Great Pacific Garbage Island, but Manila Harbour.
Since then, this highly evocative image has has become part of the myth of a solid island of garbage.   Despite efforts by scientists to bring a "reality check" to the discussion, the myth persists, as can be seen by the recent publication of two graphic novels portraying the garbage patch as a floating solid island of trash.

The Great Pacific by Joe Harris
Art from I’m Not a Plastic Bag, by Rachel Hope Allison
The reality is somewhat different.  While some large bits of debris can be found, most of the plastic pieces are are smaller than 1 cm cubed, and many can even be microscopic.  
The actual Pacific Garbage patch. Area of this photo is approximately 5′ by 10′.
Photo: Scripps Institution of Oceanography, 2009 SEAPLEX cruise.
This is not by any means to say that the garbage patch is not a problem.  Clearly, birds and fish often mistake the plastic for food, eat it, and, unable to digest it, can slowly starve to death.  Yet there are creatures that are positively thriving in this new "plastisphere" environment: water skaters, small crabs, barnacles, and bryozoans.  Some of these creatures are enjoying a veritable boom time - but this can lead to dramatic changes in the ecosystem of the ocean, especially when foreign creatures invade new areas previously inaccessible to them.  Apart from possibly doing damage themselves (like barnacles and bryozoans do to ships hulls), these new creatures also attract their predators, which can also compete for other food sources with the locals.  The plastisphere is "an ecosystem out of balance", and may pose a real threat to the long term health of the world-wide oceans.

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