Big bugs you can hug

If you’re wondering what to get the science punk in your life for Christmas, how about these adorable plush toys modelled after the great and the grisly of the microbial world? Nothing says “Season’s Greetings!” like a 7-inch flesh-eating Streptococcus pyogenes bacterium.

Giant Microbes Homepage

Add comment November 24th, 2006

The Red Herrings of Greenpeace

It must be hard for Greenpeace. Once tackling the world’s great environmental threats meant throwing yourself in front of a harpoon gun, or having your ship blown up by French spies. Today’s concerns are far more pedestrian, and it’s not easy to get people worked up about litter in the ocean. That must be why Greenpeace decided to issue a press release warning of the PACIFIC TRASH VORTEX. According to them, this swirling whirlpool of doom is collecting our garbage and concentrating it into “an area the size of Texas”, poisoning marine life and killing baby seals. They’ve got a lovely animation of the PACIFIC TRASH VORTEX which can be seen here.

Let’s have a look at a couple of the statements made in the Greenpeace press release, as reported by Reuters.

The Greenpeace report, “Plastic Debris in the World’s Oceans” said at least 267 species — including seabirds, turtles, seals, sea lions, whales and fish — are known to have suffered from entanglement or ingestion of marine debris.

Plastic pollution is a problem in all the world’s oceans, the Greenpeace report said, but underlined the issue in the Pacific by sailing through the floating garbage dump and capturing images of wildlife interacting with plastic.

Okay, firstly, I don’t believe that Greenpeace single-handedly counted 267 different species in trouble. And more to the point, sea lions are coastal, so I don’t think they’ll be hanging out in the middle of the largest ocean on Earth. Something is amiss. Secondly, I can’t find any pictures of this PACIFIC TRASH VORTEX, despite their claims. If there really is a carpet of filth coating the North Pacific, I want to see it.

The next step is to find the source of all these statements. That would be Greenpeace’s report “Plastic Debris in the World’s Oceans“, written by Michelle Allsopp, Adam Walters, David Santillo, and Paul Johnston. The first thing we notice is: this is a literature review. There’s no evidence that any of these authors have ever been to the PACIFIC TRASH VORTEX. In fact, the words “PACIFIC TRASH VORTEX” do not appear anywhere in this paper. What’s going on?

This isn’t a bad paper - something your average undergraduate would be proud of. For the most part it details various published papers that have reported the negative effects of marine pollution, and says very little about a giant swirling vortex of garbage. Then I found the following table:

Now, Wikipedia tells me that the North Pacific Gyre lies roughly between the equator and 50 degrees north. So, according to Greenpeace’s own report, the average amount of debris found here is less than one piece per square kilometer. That makes the PACIFIC TRASH VORTEX cleaner than the Arctic, North Atlantic, English Channel, Mediterranean, Southern Atlantic, Ambon Bay and the Southern Ocean. In fact, there isn’t a single area on the table with less trash than the North Pacific Gyre. So where the heck did Greenpeace get their PACIFIC TRASH VORTEX idea from? Page 28 reveals:

The North Pacific central gyre is an area of convergence where clockwise ocean currents act as a retention mechanism and prevent plastic debris from moving towards mainland coasts. A study in this region reported exceptionally high densities of plastic debris (Moore et al. 2001). Using nets to collect debris, the abundance of floating plastic averaged 334,271 pieces/km2, (range 31,982 to 969,777 pieces/km2). The results of floating plastic debris from this study cannot be directly compared with most other studies on floating debris in which debris is quantified by a different method, namely visual inspection of the ocean surface.

Now, let’s remember that phrase “cannot be directly compared with most other studies“, while we look to page 7:

Floating marine debris: studies on different areas of the marine environment reported quantities of floating marine debris that were generally in the range of 0-10 items of debris per km2. Higher values were reported in the English Channel (10-100+ items/km2) and Indonesia (more than 4 items in every m2). Floating micro debris has been measured at much higher levels: the North Pacific Gyre, a debris convergence zone, was found to contain maximum levels, that when extrapolated represent, near to a million items per square kilometre.

So, which is it? Does the North Pacific contain one piece of garbage per square km? Or one million? You’d think with Steve Smith “finding a lot of stuff out here, floating by” and with “inflatable boats dispatched from the ship to collect samples”, Greenpeace might be able to narrow down the garbage density to ooh, say, a power of 10 or so. Of course, that might meaning telling the truth: there is a lot of garbage out there, but it’s spread over 34 million square kilometers. The environmental problems that Greenpeace highlighted are happening, but for the most part, not in the North Pacific (well, it beats living in Ambon Bay, put it that way). This is because Greenpeace, though good at getting headlines, aren’t very good at science. Until they find another harpoon gun to jump in front of, expect more sensationalistic press like this from our errant eco warriors.

32 comments November 24th, 2006