By Alex Kirby
BBC News website environment correspondent
Some genetically-modified crops can be managed in a way that is beneficial to wildlife, a UK research team believes.
The study says wildlife could gain (Image: John Robinson/English Nature)
Their work, published by the Royal Society, says there is "conclusive evidence" of benefits to wildlife from GM sugar beet crops.
They say their findings mean everyone involved in the debate about GM crops should rethink where they now stand.
But anti-GM campaigners say the work changes nothing, and are still opposed to any use of the crops in the UK.
The researchers are from Broom's Barn Research Station, part of Rothamsted Research, which specialises in the study of sugar beet.
The study, Management Of GM Herbicide-tolerant Sugar Beet For Spring And Autumn Environmental Benefit, was funded in 2001 and 2002 by a consortium of GM industry interests, the Association of Biotechnology Companies (ABC).
But the researchers say they accepted the support on condition that they could publish their work with no restrictions or reference to the ABC.
To help wildlife in spring, the researchers say, they improved the timing of herbicide application to maximise crop yields and the benefits from leaving weeds between crop rows.
Answering the doubters?
For the more important autumn environmental benefits (weed seeds for bird food and for recharging weed seedbanks), they say they developed a system giving maximum crop yield and increased weed seed availability (up to 16-fold).
This is by comparison with previous GM or conventional management systems tested in the government's recent Farm Scale Evaluation (FSE) trials.
The team says: "The new system is extremely simple: compared to the previous GM management system, it involves applying the first spray fairly early and omitting the second spray."
Lack of food is harming many farmland birds
The researchers say their new crop management approaches "could resolve legitimate concerns about indirect environmental effects of GM sugar beet on weeds, insects and birds".
Dr John Pidgeon, director of Broom's Barn, told the BBC: "We're scientists, and we go by the evidence. We think this is all about how you manage the crops, not whether they're genetically modified or not.
Beyond academic interest
"If you manage the crop differently and to benefit the environment, you get a different result. Perhaps all sides of the GM debate need to think again.
"Although the government has ruled out the growing of GM beet, this research could undoubtedly have a commercial application if anyone decides to take it up."
Campaigners say birds will still go hungry
But the Five Year Freeze Campaign said the research showed different management approaches would leave farmland wildlife short of food at some stage of the year.
It said Broom's Barn had used two techniques on the beet to increase weed cover or seed production, band spraying early in the season or delayed spraying. But only one technique could be used, it said.
The campaign's director, Pete Riley, said: "The choices offered by GM sugar beet cropping appear to offer farmland birds three options: insufficient food throughout the year, early season food or autumn food.
"We doubt that this last ditch attempt to save GM sugar beet will have much credibility with regulators or farmers."