Benefits to biodiversity are 'reduced but not eliminated'

The benefits to wildlife of growing genetically modified maize - the only GM crop to demonstrate environmental advantages - will not be as great as predicted, a study published today has found.

The benefits to wildlife of growing genetically modified maize - the only GM crop to demonstrate environmental advantages - will not be as great as predicted, a study published today has found.

Scientists studying the effect of the ban of a highly toxic weedkiller which comes into effect next year have found that the advantages of growing GM maize will be "reduced but not eliminated".

When the results of the field-scale trials of three GM crops were published last year, only GM fodder maize seemed to benefit the wild flowers, insects, butterflies and other wildlife living with the crops.

This was because the herbicide used with non-GM maize, called Atrazine, was so persistent and toxic that it was more effective than the weedkillers used with GM maize.

The scientists involved with the farm-scale trials found that there were about two or three times as many weeds, seeds and invertebrates living in the fields of GM maize than in the fields of non-GM maize sprayed with Atrazine.

Environmentalists said that these findings would be invalid once Atrazine and other related herbicides are banned following a European directive which comes into force in 2005.

The scientists compared the wildlife living in GM maize fields with fields of non-GM maize sprayed with more benign weedkillers than Atrazine.

About a quarter of the non-GM maize in the field trials was sprayed with non-Atrazine weedkillers and the scientists, led by Professor Joe Perry of Rothamsted Research in Harpenden, Hertfordshire, found they harboured more wildlife than the non-GM fields sprayed with Atrazine - but still not as much as the GM fields.

Their study, published in the journal Nature, found that the amount of wildlife living in fields of GM maize was about 1.5 times higher than in those fields of conventional maize sprayed with non-Atrazine weedkillers - about a third less than previously stated.

"The environmental benefits of growing GM maize will be reduced but not overturned once Atrazine is taken off the market," Professor Perry said.

"This supports the previous conclusions that there is unlikely to be an adverse effect of growing GM maize in terms of biodiversity," he said.

Part of the problem with growing fodder maize - corn-on-the-cob for animal feed rather than for human consumption - is that it needs a lot of weedkiller to prevent it being strangled by native weeds.

Non-GM maize is best grown by first spraying the field with Atrazine to kill off the weeds in the crucial days when the seedlings start to grow. Unfortunately this persistent herbicide is too effective in terms of killing off wildlife.

GM maize, on the other hand, can be sprayed with broad-spectrum herbicides at different points in the crop cycle, in effect allowing some weeds to persist over the winter months, providing food for insects and birds.

Brian Johnson, a GM specialist at English Nature, said that on the grounds of biodiversity it would be better for farmers to grow GM maize than non-GM maize even when they use herbicides other than Atrazine.

"It is better for biodiversity because it allows farmers to leave a weedy stubble at the end of cultivation," Dr Johnson said.

The issue of whether to allow the commercial cultivation of GM fodder maize depends on wider issues such as the possible cross-pollination with organic crops and the problem of legal liability if anything went wrong, he said.

"Most important, if there is no market for this crop, it will not be grown, and many supermarkets have said that they will not buy meat from animals fed on GM maize," Dr Johnson said.

The Government's decision on whether to back the commercial cultivation of genetically modified crops in the UK will be formally announced next week.