As a keen supporter of the environment myself, one of the biggest problems with the environmental movement is a tendency to exaggerate. One of the worst examples of this right now surrounds Project Karsei, an expedition to the "Great Pacific Garbage Patch" or the "Pacific Trash Vortex," the uncritical reporting of which tends to be riddled with questionable science and statistics.

Judging by the experience of other writers tackling this subject, I'm probably going to get some flak for this, so I'll metaphorically duck behind senior Greenpeace scientist David Santillo, who has said:

"The problem with superlative statements that this is somehow a huge floating mass of plastic is that they inevitably lead to desensitizing people when they learn the truth of it."

And the superlatives come thick and fast. The Ocean Voyages Institute ludicrously talk with almost religious fervour of...

...the plastics which are converging in the Pacific ocean and forming an 8th continent. Never heard of it? You need to help us. This is a rescue mission designed to save the Pacific by mining plastic. This 8th Continent has been identified northeast of Hawaii in the Pacific. Sailors and scientists, fishers and individuals have watched with horror, as this new continent comprised of human discards, primarily plastic garbage, has grown and expanded exponentially over the last few years. Also called the plastic vortex, this 8th continent is currently twice the size of Texas and growing.

Environmentalist David Suzuki talks of "a massive, expanding island of plastic debris 30 metres deep and bigger than the province of Quebec", while Greenpeace themselves - no stranger to exaggeration - describe "one of the world’s largest floating garbage dumps." Newspaper reports sourced talk of there being six-to-eight times more plastic than plankton.

Some of these claims are obviously absurd - an 8th continent?! - but as John Zhu has eloquently pointed out, journalists reporting on the "trash vortex" have failed to really challenge the people they're reporting on, or draw on research to add context to their efforts.

In particular, a debate has sprung up recently around the reporting of Lindsay Hoshaw, a Spot.us community-sponsored journalist whose report on Project Karsei - an environmentalist research project sailing in the region - ended up in the New York Times.

The Spot.us community paid Lindsay Hoshaw $10,000 to visit the region, but appear to have received little in the way of incisive journalism for their money, with the result coming across as a fairly uncritical travel blog (an excellent criticism of which can be found here, or here). Should they have sent her in the first place? Zhu makes the following excellent point:

"Maybe instead of paying for someone to go take pictures of the patch, that $10,000 should go to paying for a reporter to sit in a room somewhere, sift through reams of research data on the subject, visit fisheries, interview scientists, doctors, policy makers … It’s not as exciting as a trip to the garbage patch and certainly lacks that “once-in-a-lifetime” appeal, but it may be the better route toward actually getting good journalism on the subject."

Exactly.

Which brings me neatly to the science itself. I'm not an ocean scientist, but I do have some experience of ocean modelling, and many of the claims being made ring alarm bells.

Let's take the comparison with plankton first. When somebody makes the claim that there is x times more plastic than plankton, the obvious first question any journalist should ask is "well how much plankton is there?"

The image below shows concentrations of Chlorophyll A in the ocean, measured by satellite, the level of which can be used as a proxy for the amount of plankton in the water (through Ocean Color algorithms beyond the scope of this blog post). Below it I've reproduced the colour scale, courtesy of NASA.

Chlorophyll A

All you need to know is that the purplest areas have 0.01mg/m³ of chl-A, while the green areas have 1mg/m³ and the reddest areas have about 50-60mg/m³. In other words, some areas of the central Pacific have almost 100x less plankton than, say, the North Atlantic does, and as much as 5,000x less than parts of the Baltic sea or English channel.

Plankton don't generally live in great quantities inthe middle of oceans, so saying that there are 'x' lbs of plastic vs 'x' lbs of plankton is a bit like seeing a washing machine dumped in the middle of the Sahara and returning home to announce that washing machine parts outnumber grass in parts of the desert.

There are (comparatively) sod-all plankton in the mid-Pacific, and six times sod-all is still sod-all, a point starkly made by Greenpeace's own data, when they compile a table of the relative plastic content of the world's seas and oceans (Figure 4.15, on P30) (HT: Science Punk):

It should be noted that these are figures from visual inspection, and the amount of plastic that can be caught by nets may be far higher, but the point remains that there are other places with a far greater quantity of surface plastic than the North Pacific, making it frankly puzzling that just so much attention has been devoted to surface plastic in this area. Indeed, we can look at lot closer to home, at the English Channel, to find far more concerning levels of contamination that are orders of magnitude higher.

This is not to say that regions of high plastic contamination don't exist in the Pacific. Indeed, the NOAA describe two areas in the pacific, the North Pacific Subtropical High and the North Pacific Subtropical Convergence Zone (STCZ) (media reports generally refer to the former). The size of these areas though is highly variable, and unknown, meaning that guesstimates by activists should be taken with a pinch of salt.

It is therefore not at all clear that these patches are growing, and Hoshaw's assertion that the Texas-sized trash vortex "doubles in size every decade" is at best unevidenced and at worst made-up.

In the Atlantic, attempts to measure growth have been inconclusive. The Sea Education Association have got 22 years' worth of data on the North Atlantic and Carribean, centering on a high plastic concentration at about thirty degrees north. The interesting thing from their data is that the quantity of plastic found hasn't increased in the 22 years they've been measuring it. That doesn't mean there isn't more there somewhere, but certainly something curious is happening to it.

Researchers with that group describe the phenomenon as a "plastic soup", a much more appropriate description and in some ways more alarming: "It’s much worse. If it were an island, we could go get it. But we can’t, because it’s a thin soup of plastic fragments."

Even the effects of the plastic on life are not as clear-cut as reports would suggest. We know that many animals ingest small particles of plastic, but the end result of this is unclear and probably depends on the species. It is easy to post a photo of a dead chick with plastic in its stomach, and claim that the plastic was the cause of death; but far harder to back this up with evidence. Indeed, studies of albatross chick mortality in Hawaii in the late-1980s found no evidence of plastic related mortality.

It's additionally worth bearing in mind the vagueness about where these photos were taken, and the lack of experimental rigour inherent in surveying contents by taking random photos. Personally I do believe plastic is likely to poison or kill some life, but we need more information about the precise extent. As shocking as these images are, they add little to our scientific knowledge of the problem.

It's difficult to cover this problem without being accused of anti-environmentalism. That isn't the case - plastic contamination in the oceans simply shouldn't be there, and there's no doubt that this is a problem that needs to be taken seriously. However, by attempting to spin tales of plastic "continents", environmentalists risk shooting themselves in the foot. People have little patience for such easily debunked claims, and there's a real danger of being the boy who cried wolf.

What we need aren't publicity stunts and travel blogs, but comprehensive research to understand the true extent of the problem, and what we can do about it. Feeding myths to the media doesn't aid this understanding, it simply misleads the public, and ultimately undermines those of us trying to pitch a rational, environmentalist message.

You don't need to invent an eighth continent to persuade people that plastic in the oceans is a problem.