Guest Post by Willis Eschenbach
I read a paper today that said that there are no less than 270,000,000 kilograms of plastic in the ocean, which is about half a billion pounds plus of plastic. So … is this a big number or a small number?
The story is at the Guardian, and they’ve illustrated it with the following picture:
Regarding the story, as usual the Guardian doesn’t disappoint—it hypes the danger of the half-billion pounds of plastic. Hey, good news doesn’t sell newspapers, so I can’t fault them. In any case, they say:
More than five trillion pieces of plastic, collectively weighing nearly 269,000 tonnes, are floating in the world’s oceans, causing damage throughout the food chain, new research has found.
Now, I suppose that the good folks at the Grauniad think that with their picture they are showing the “damage throughout the food chain” that they claim plastics cause in the ocean … but look at the picture and think about it for a moment.
Does it look like a) that chunk of plastic is inimical to sea life … or does it look like b) that chunk of plastic is acting a substrate upon which abundant sea life is living and serving as fish food? Call me crazy but I’m going for Choice b), you can see the little striped fish chowing down. Now I know that not all plastic is good for sea life … but that plastic certainly is.
However, I started out with the question about whether 270,000,000 kilogrammes is a big number or a small number. Looking at the extent of the ocean gives us a very different picture … because it turns out that the 270,000,000 kilograms of plastic works out to 200 grams of plastic per cubic kilometer of the ocean. Or in old-school measurements, that’s just under two pounds of plastic per cubic mile of seawater. (Some commenters have noted that most of the debris is at or near the surface, so if you prefer, it’s about 900 grams of plastic per square kilometer of ocean surface.)
Now, I’m willing to agree that there are some kinds of plastic that are likely inimical to sealife. Nylon fishing nets that have been lost and gone adrift, for example, continue to kill fish. But the fish aren’t wasted, they’re eaten in turn by a combination of larger and smaller fish until the net washes ashore. So the nets are just another predator. Not saying I like that, I don’t, particularly when they catch whales and other sea mammals … but it’s not the end of the ocean.
And as for the other small pieces of random plastic … well, I just can’t get all that passionate about the dangers of 200 grams of plastic for every BILLION tonnes of sea water, or if you prefer, the dangers of 900 grams of plastic for every square kilometre of ocean surface (1 cubic km = one billion tonnes).
Now, I can hear you thinking, but Willis, what about the great Pacific Gyre, where the plastic collects? First, it’s not like most people think, where you could walk on the plastic and there are islands and such. The density is much higher than the global average, but it’s still only about 2-3 kg per cubic kilometre, or about 5 kg/square km.
However, as a long-time fisherman, I’d bet big money that there is MORE sea life in the Gyre than in equivalent blue-water ocean near the Gyre. The blue water is a desert, in part because there’s nothing for life to grow on. Many kinds of sea life require a “substrate”, something solid to attach to so it can grow. As a result, anything that floats, and I mean anything, will rapidly attract life, just as in the Guardian’s “scary” picture above.
In closing, I don’t like plastic in the ocean, and I’m very, very conscious about it when I’m at sea. I never throw plastic into the ocean. However, as an ocean problem, it’s way, way below things like overfishing and pollution. Those are the real dangers, not a couple hundred grams of plastic in each billion tons of sea water. That’s a small number.
Best to all,
PS—If you disagree with someone, please QUOTE THEIR EXACT WORDS so everyone can be clear just what your objection might be.