Scientists and environmentalists have attacked a global campaign to ban plastic bags that 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 of London. They pose only a minimal threat to most marine species, including seals, whales, dolphins and seabirds.
British Prime Minister 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, and similar movements have spread across the United States.
But scientists, politicians and marine experts attacked the British government for joining a “bandwagon” based on poor science.
“The Government is irresponsible to jump on a bandwagon that has no base in scientific evidence," said Lord Taverne, the chairman of Sense about Science. "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.”