October 10, 2009

TIME for Kids – the Plastic Vortex

Filed under: Uncategorized — tommoriarty @ 1:59 am
Tags: , ,

I don’t know if it is naive credulity or sinister complicity, or some combination of them both, that allows writers to so easily echo  environmental hyperbole.   The September 25 issue of TIME for Kids (TIME Magazine’s version of the “Weekly Reader”) had and article by TIME’s Bryan Walsh called “The Big Garbage Patch.”

Walsh tells fifth and sixth grade readers about the “Plastic Vortex,”

“an accumulation of plastic debris swept into the Pacific.  The garbage comes directly from beaches or flows out of rivers.  It is carried by ocean currents in a swirling pattern to a spot between Hawaii and the mainland United States”

The Big Garbage Patch 2
I first heard about this article when my 10-year-old son came home from school and asked if it was true “that there is enough plastic floating in the Pacific Ocean to cover Texas twice?”  After he explained the article to me, I assured him that he must have misunderstood, and I asked him to bring the article home so I could read it myself.  Sure enough, Walsh tells the kids…

“Plastic bags, bottles and toys end up in the vortex.  Some scientists estimate it to be twice the size of Texas. ‘it’s huge,’ notes Doug Woodring, an ocean conservationist.  But ‘unfortunately the ocean is a big place,and once [the garbage is] out of sight, it’s out of mind.'”

So there you have it.  Nothing subtle about that “twice the size of Texas” claim. 

A little more research into the subject reveals the “Plastic Vortex” was discovered by Charles Moore in 1997.  How something “twice the size of Texas” had stayed hidden until Moore stumbled upon it is a mystery to me.   Mr Moore, who subsequently founded the Algalita Marine Research Foundation, is widely quoted as claiming 100 million tons of plastic flotsam are circulating in the region.

Let’s see, Texas is about 700,000 km2.  So twice that is 1.4 million km2.   So on average there must be about 70 tons of plastic per km2*   I am wondering if that is just a wee bit of an exaggeration, because roughly speaking, that is about a pound of plastic for every 9 foot by 9 foot patch of the ocean in “Plastic Vortex.”**

Curiously increased estimates

I’m thinking Mr. Moore has ratcheted up his estimates slightly in the last few years.  Back in 1999 Mr. Moore actually published a paper that had a reasonable approach to making an estimate of the amount of plastic in this region.

Basically, he pulled a kind of small net net, called a manta trawl, through the area of the vortex with the highest density of plastic.  The holes in the net were 333 microns wide (or 1/3 mm).  This net was dragged repeatedly for three days with runs ranging from 5 to 19 kilometers.  After each run all the debris in the net was recovered and saved.  All the gunk was fixed in formalin and then soaked in 50% isopropyl alcohol.  Finally, all the plastic was separated from the biological material that was also trapped in the net. 

Moore and his colleagues counted 27,698 pieces of recovered plastic.  But they were pretty small pieces – their total mass was only 424 grams (0.93 pounds).  His net only sampled about 1/12 km2,  so he calculated about 5.1 kg of plastic per km2 (or about 11 pounds of plastic per km2).  

Somehow in the last 10 years Moore’s claims for the amount of plastic in the vortex has gone from a measured value of 11 pounds per km2  to an estimated 140,000 pounds per km2.

A plastic bag every square meter?

If there were, indeed, 100 million tons of plastic in the Plastic Vortex, from where did it possibly all come?  We are told that some of the largest components are from disposable plastic bottles and plastic grocery bags.  Lets just play along for a moment and say that 10% of this massive amount of plastic, or 10 million tons, is from plastic grocery bags.  

I went to my local grocery store a few days ago and weighed a bundle of plastic grocery bags.  The 80 bags in the bundle weighed 0.85 pounds.  Thats about 100 bags per pound.  So those 10 million tons of plastic bags would be equivalent to two trillion bags.***  Where could all these bags come from?  Those nasty litterers in the United States?  Not likely, since the wind that would carry this torrent of plastic blows primarily toward land on the western shores of the US, not toward the sea.

Lets keep playing along for moment and suppose the 54 million people living in California, Oregon, Washington State and British Columbia ARE responsible for two trillion plastic bags in the Plastic Vortex.  That works out to about 40,000 bags per person.  Those folks on the west coast must be buying a lot of groceries.

One more point about the plastic bags:  These 2 trillion bags spread out over and area twice the size of Texas would work out to more than one bag per square meter!!****  And that is just 10% of the supposed 100 million tons of plastic!!  

Why the preposterous exaggeration?

I think you can see my point.  The claim that there are 100 million tons of plastic in the Plastic Vortex is simply ridiculous.  Moore and company are using claims designed to influence the innumerate.  Why?  They have probably found the wilder they make their claims, the more funding and contributions they get.  What impresses you, the potential donor, more: 5.1 kilograms of plastic pre km2, or 100 million tons of plastic?

Why does TIME for Kids go along with this nonsense?  It may be that the article’s author, Bryan Walsh, is innumerate, or a lazy journalist, or the people at the magazine think that environmental guilt is good for your kids.


* 100,000,000 tons of plastic / 1.4 million km2 = 70 tons of plastic per km2 

** 1 million m2 / 140,000 pounds = 7.1 m2  per pound = (2.7 m)2 / pound = (8.9 ft) 2  / pound

***  10 million tons is 20 billion pounds.  2o billion pounds x 100 bags per pound = 2 tillion plastic bags

**** twice the size of Texas = 1.4 million km = 1.4 trillion m2.  2 trillion bags / 1.4 trillion m= 1.5 bags / m2.



  1. you missed an important part in the article that you quoted:

    Plankton abundance was approximately
    five times higher than that of plastic, but the mass of plastic
    was approximately six times that of plankton.

    more plastic than plankton. sounds like a serious issue to me…

    Comment by sod — October 20, 2009 @ 8:16 am | Reply

  2. Dear Sod,

    You are correct. The ratio that you mention has been widely echoed on the internet. It sounds alarming…but it isn’t.

    The natural density of plankton in the mid-oceans is very low. This fact has nothing to do with the amount of plastic present. Plankton thrives near the coastlines and over the continental shelves where the proper nutrients are plentiful. You can see this for yourself. In the mid-ocean, where the “plastic vortex” resides, those nutrient are not present, so there is naturally very little plankton

    This is grinding 5 kilograms of plastic in to dust and spreading over a square kilometer of the Sahara Desert. Then you could say “the mass density of plastic is maybe 100 times greater than the mass density of grass.” So what?

    It sounds alarming…but it isn’t.

    Best Regards,

    Comment by Tom Moriarty — October 22, 2009 @ 5:11 pm | Reply

  3. Hi Tom,

    Thanks for the research. I would love for Mr. Moore to break down his own in such a manner.

    As is, he hasn´t, which has indeed led to mischaracterization by at times irresponsible media. The linked article from the Independent is absurd. This article (http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/10/30/MNT5T1NER.DTL&type=printable) from 2007 in the SF Chronicle has a more modest number of 3 million tons, also called ¨an estimate¨ of Mr. Moore´s. It shows two things: (a) that Mr. Moore is not in fact widely claiming this 100 million ton number, and (b) that PR at Algalita is something of a joke and contributing to bogus media coverage that hurts the cause, sensationalizing the issue and desensitizing the concerned public.

    My concern, Tom, is that you got desesitized. The Sahara analogy regarding plankton density in the ocean is really interesting, and relevant to Algalita´s ratio claims. But the fact of the matter is that more and more plastic is entering our ocean, it´s not going anywhere, and it´s affecting the ecosystem (check out the lantern fish analysis at AMRF Annual Report: http://www.algalita.org/pdf/amrf-annual-report-2008.pdf).

    I´m all about holding researchers, media, and educators accountable, but I also hope your son is on board with reusable bags and water bottles. It´s not about guilt, it´s about responsibility.


    Comment by Matt — October 28, 2009 @ 10:30 am | Reply

  4. For everyday people it becomes harder and harder to seperate the science from the pseudoscience and if you think about what our children are inheriting they are the ones that have to make changes to their way of life, because – sure as eggs- adults won’t. If adults are so quick to defend the status quo, then how can we expect children to dicern the truth? As soon as someone like Mr Moore comes along and gives the public a reason to doubt they latch onto it and worse, malign the very people trying to expose the truth.
    In terms of plastic, there is more and more. Most notably – clingwrap around every stack of product boxes on a crate, silage and hay wrap, (same thing cling wrap around every hay bail or silage), every part of the interior of a car, bundles of newspapers, it just goes on.

    Comment by teresa rudgley — February 2, 2010 @ 12:50 am | Reply

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