Series of blunders turned the plastic bag into global villain

Scientists and environmentalists have attacked a global campaign to ban plastic bags which they say is based on flawed science and exaggerated claims. The widely stated accusation that the bags kill 100,000 animals and a million seabirds every year are false, experts have told The Times. They pose only a minimal threat to most marine species, including seals, whales, dolphins and seabirds. 

Gordon Brown announced last month that he would force supermarkets to charge for the bags, saying that they were "one of the most visible symbols of environmental waste". Retailers and some pressure groups, including the Campaign to Protect Rural England, threw their support behind him. 

But scientists, politicians and marine experts attacked the Government for joining a "bandwagon" based on poor science. Lord Taverne, the chairman of Sense about Science, said: "The Government is irresponsible to jump on a bandwagon that has no base in scientific evidence. This is one of many examples where you get bad science leading to bad decisions which are counter-productive. Attacking plastic bags makes people feel good but it doesn't achieve anything." 

Campaigners say that plastic bags pollute coastlines and waterways, killing or injuring birds and livestock on land and, in the oceans, destroying vast numbers of seabirds, seals, turtles and whales. However, The Times has established that there is no scientific evidence to show that the bags pose any direct threat to marine mammals. They "don't figure" in the majority of cases where animals die from marine debris, said David Laist, the author of a seminal 1997 study on the subject. Most deaths were caused when creatures became caught up in waste produce. "Plastic bags don't figure in entanglement," he said. "The main culprits are fishing gear, ropes, lines and strapping bands. Most mammals are too big to get caught up in a plastic bag." 

He added: "The impact of bags on whales, dolphins, porpoises and seals ranges from nil for most species to very minor for perhaps a few species.For birds, plastic bags are not a problem either." 

The central claim of campaigners is that the bags kill more than 100,000 marine mammals and one million seabirds every year. However, this figure is based on a misinterpretation of a 1987 Canadian study in Newfoundland, which found that, between 1981 and 1984, more than 100,000 marine mammals, including birds, were killed by discarded nets. The Canadian study did not mention plastic bags. 

Fifteen years later in 2002, when the Australian Government commissioned a report into the effects of plastic bags, its authors misquoted the Newfoundland study, mistakenly attributing the deaths to "plastic bags". The figure was latched on to by conservationists as proof that the bags were killers. For four years the "typo" remained uncorrected. It was only in 2006 that the authors altered the report, replacing "plastic bags" with "plastic debris". But they admitted: "The actual numbers of animals killed annually by plastic bag litter is nearly impossible to determine." In a postscript to the correction they admitted that the original Canadian study had referred to fishing tackle, not plastic debris, as the threat to the marine environment. Regardless, the erroneous claim has become the keystone of a widening campaign to demonise plastic bags. 

David Santillo, a marine biologist at Greenpeace, told The Times that bad science was undermining the Government's case for banning the bags. "It's very unlikely that many animals are killed by plastic bags," he said. "The evidence shows just the opposite. We are not going to solve the problem of waste by focusing on plastic bags. "It doesn't do the Government's case any favours if you've got statements being made that aren't supported by the scientific literature that's out there. With larger mammals it's fishing gear that's the big problem. On a global basis plastic bags aren't an issue. It would be great if statements like these weren't made." 

Geoffrey Cox, a Tory member of the Commons Environment Select Committee, said: "I don't like plastic bags and I certainly support restricting their use, but plainly it's extremely important that before we take any steps we should rely on accurate information. It is bizarre that any campaign should be endorsed on the basis of a mistranslation. Gordon Brown should get his facts right." 

A 1968 study of albatross carcasses found that 90 per cent contained some form of plastic but only two birds had ingested part of a plastic bag. 

Professor Geoff Boxshall, a marine biologist at the Natural History Museum, said: "I've never seen a bird killed by a plastic bag. Other forms of plastic in the ocean are much more damaging. Only a very small proportion is caused by bags." Plastic particles known as nurdles, dumped in the sea by industrial companies, form a much greater threat as they can be easily consumed by birds and animals. 

Many British groups are now questioning whether a ban on bags would cost consumers more than the environmental benefits. Charlie Mayfield, chairman of retailer John Lewis, said that tackling packaging waste and reducing carbon emissions were far more important goals. "We don't see reducing the use of plastic bags as our biggest priority," he said. "Of all the waste that goes to landfill, 20 per cent is household waste and 0.3 per cent is plastic bags." John Lewis added that a scheme in Ireland had reduced plastic bag usage, but sales of bin liners had increased 400 per cent. 

`Sexed-up' numbers should not always be accepted as science

By Mike Hulme (Mike Hulme is a professor in the School of Environmental Sciences at the University of East Anglia)

In the recent flurry of moves to ban plastic bags a frequently cited statistic is that more than 100,000 marine mammals and sea turtles die each year from entanglement in, or ingestion of, plastic bags. The original scientific study upon which this estimate relied actually attributed these deaths to fishing tackle in the oceans, not plastic bags. Yet the terms "100,000 marine deaths" and "plastic bags" now circulate happily through our public discourse, solidified as established fact. 

But when is a fact a fact? Can facts change over time? And does it matter if they do? Science is instinctively referred to as the source and authenticator of facts such as the one cited above, and rightly so. Yet as this example shows, we need to be very careful about the veracity of the numbers we latch on to, and about what they signify. What may start out as a credible, yet qualified and provisional, scientific estimate may end up, either through distortion or mere negligence, enduring as an urban myth, apocryphal numbers - the modern equivalent of folklore. 

My own area of climate change offers plenty of such examples. In December 2005 a study in the journal Nature offered the observation that the circulation in the North Atlantic Ocean, which sustains the Gulf Stream, had weakened by up to 30 per cent over the previous few decades. This figure and its juxtapositioning alongside the melodrama of films such as The Day after Tomorrow were amplified through the cooperation of scientists and media to result in headlines such as "Alarm over dramatic weakening of Gulf Stream" ( The Guardian, Dec 1, 2005). The urban myth that emerged from this episode was that we were closer to a mini Ice Age in the UK than had previously been thought. Eighteen months later, however, and unremarked by the media, two studies in equally reputable journals pointed out that such a trend was within the range of natural variability and may signify nothing at all. 

A second example concerns the claim that, "by the end of this century, climate change will have killed around 182 million people in sub-Saharan Africa" (Christian Aid, May 2006). This number - 180 million African dead - has become one of the most widely cited numbers in the litany of doom that accompanies talk of climate change. In this case, however, the number 180 million was sexed-up science. Christian Aid took the worst-case climate scenario, the highest population scenario and the scenario with the least public health intervention and conjured the number into being. And here it has stayed, a number detached from its receding scientific origins in which assumptions were overlain on scenarios that captured uncertainties.

Whether through being lost in translation, through the premature citing of provisional science or through the purposeful sexing-up of deeply uncertain numbers, the facts of science are not always to be taken at face value. 

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