FEARS about genetically modified foods are back on the agenda. But the idea that genetic modification is in itself harmful now appears to be a minority viewpoint.
Next month, California votes on Proposition 37, which would require the labelling of all foods containing GM ingredients (see 鈥�Not on the label鈥�). In the run-up, one prominent study claimed that GM technology is bad for health.
However, major reports in the US and Europe have concluded that the technology is a lot more benign than is generally assumed to be the case. There is even evidence that transgenic crops are beneficial in ways we are only beginning to appreciate.
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It can seem almost impossible to find reliable information on GM crops. Even peer-reviewed scientific studies can trigger a storm of controversy.
Last month, Gilles-Eric S茅ralini of the University of Caen in France reported that rats became more susceptible to cancer when fed GM maize with inbuilt resistance to the herbicide glyphosate (Food and Chemical Toxicology, ).
Other GM researchers were quick to point out flaws in the study, including the fact that many of the control mice on a non-GM diet also developed cancer. S茅ralini鈥檚 paper did not include the necessary statistics to assess whether the differences between control and test mice were significant. On 4 October, the announced that the paper was of 鈥溾��.
Aside from such health fears, government agencies are unconvinced that GM technology poses an environmental threat.
In 2010, for example, the US , and concluded: 鈥済enerally, GM crops have had fewer adverse effects on the environment than non-GM crops produced conventionally鈥�. The same year, a , saying GM crops 鈥渁re not per se more risky鈥�.
鈥淕enerally, transgenic crops have had fewer adverse effects on the environment than conventional ones鈥�
Even conservationists are coming around to the same view. In 2004, the , but by 2007 it had saying there was 鈥渘o conclusive evidence of direct negative impacts on biodiversity of GMOs that have been commercially released鈥�.
That鈥檚 largely because studies claiming that GM crops are environmentally harmful are difficult to back up.
Most of these studies focus on one type of transgenic crop 鈥� those that are resistant to herbicides, meaning they can be liberally sprayed without harm. It鈥檚 easy to imagine how herbicide-resistant crops might encourage farmers to spray their fields 鈥� and a study published last month suggests there is truth to the claim.
Charles Benbrook of Washington State University in Pullman, concluded that herbicide-resistant crops caused an extra 239 million kilograms of herbicide to be sprayed in the US between 1996 and 2011 ().
But those figures are based on a number of assumptions, says of PG Economics, a consultancy firm in Dorchester, UK, that examines the impact of new technology on agriculture.
Brookes says there are few studies comparing herbicide use in GM and non-GM crops, and comparison is becoming increasingly difficult because of the popularity of transgenic crops 鈥� for instance, 94 per cent of soya planted in the US in 2011 was genetically modified.
Benbrook鈥檚 figures on herbicide use came from the US , but the database does not distinguish GM and non-GM crops. He had to estimate how much herbicide per hectare was used on each, by assuming from the type of herbicides whether the crops in a given area were transgenic or not.
Brookes has taken a different approach. Supported by biotech industry funding, he surveyed industry specialists to estimate how much farmers would spray if they were not using herbicide-resistant GM crops.
His results suggest that, between 1996 and 2010, GM crops may actually have reduced worldwide herbicide and insecticide use by 9.1 per cent compared with a GM-free scenario ().
There is an explanation, says Brookes. Traditional herbicides don鈥檛 work on all weeds and so farmers must spray their fields several times. Glyphosate, which attacks most weeds, can be sprayed fewer times for the same effect, so glyphosate-resistant crops need less spraying.
Both Brookes and Benbrook agree that a second technology has firm green credentials, though. Some GM crops produce chemicals that kill insects, fending off pests without the need for insecticide. A 2006 study by of the University of Arizona in Tucson showed that insect-resistant cotton harms biodiversity less than conventional cotton sprayed with insecticides () . By 2000, the rise of glyphosate-resistant crops had cut the use of older herbicides, which in the environment and were more toxic to animals ().
Still, these improvements are a double-edged sword. According to the , 22 weed species are now resistant to glyphosate. Some insect-resistant crops are also losing their effectiveness.
Critics blame GM for resistance. Hartmut Meyer of the European Network of Scientists for Social and Environmental Responsibility says biotech companies produce GM crops resistant to a small range of pesticides, limiting farmers鈥� choice and overexposing pests to the same chemicals, encouraging them to evolve resistance.
鈥淏iotech firms produce GM crops resistant to a small range of pesticides, encouraging resistance鈥�
Such problems reflect the way GM crops have been marketed rather than underlying flaws in the technology, though. Producing a wider range of GM crops could reduce the likelihood of resistance emerging by allowing farmers to switch the chemicals they use before pests evolve resistance.
Not on the label
Next month, voters in California are likely to approve , which requires all genetically modified food to be labelled as such, and prohibits it from being marketed as 鈥渘atural鈥�. A recent LA Times poll found that . Campaign group argues that people have a right to know what is in their food, and (see main story) in its campaign materials.
An opposition group, , argues that the law would cost over $1 million per year. The No campaign is funded by a range of major biotech and food companies, and has received , according to a report by research organisation MapLight.
Proposition 37 has some key limitations that mean consumers would often be . GM crops are often used as animal feed in the US, but meat from such animals would not have to be labelled. Nor would alcoholic drinks or processed foods containing genetically engineered enzymes.
The US Department of Agriculture regulates the production of GM crops, but companies are now using techniques that do not fit the USDA鈥檚 definitions (). For instance, rather than inserting new genes, some companies inject proteins to alter existing genes. Some of these techniques would also slip through Proposition 37鈥檚 net.
