UK's GM crop trials not relevant to us: CSIRO

The findings of a British study of the impact of genetically modified, herbicide-tolerant (GMHT) crops on farm biodiversity are critical to the future of GM crops in Britain, but have little relevance to Australia, CSIRO experts have concluded.

CSIRO Entomology plant ecologist Dr Mark Lonsdale, and Dr Mikael Hirsch, head of CSIRO's Biotechnology Strategy Group, reviewed the results of Britain's £5 million Farm Scale Evaluation (FSE) project, released two weeks ago by the Royal Society.

Lonsdale said the world's largest study of the effect of GM crops on biodiversity was established after a paper in Science several years ago predicted GMHT sugar beet would threaten Britain's skylark population by decimating its favourite food source, the common farm weed fat hen (Chenopodium).

Research has implicated the intensification of agriculture in the long-term decline of native bird populations.

The FSE project compared the impacts of GMHT sugar beet, maize and spring canola with those of their non-GM equivalents, on weed density and invertebrate populations on UK farms -- the results for a fourth crop, winter canola, have yet to be published.

Of the four crops, only GMHT spring canola is being grown in Australia, and only in small-scale experiments, because state governments have imposed an effective Australia-wide moratorium on GMHT canolas.

Lonsdale and Hirsch, who visited the UK to see the trials in progress, delivered a report on their analysis to the CSIRO executive this week.

"It was a fantastic experiment, that should inform future research," Lonsdale told Australian Biotechnology News. "The findings are critical to the future of GM cropping in the UK. But they can't be extrapolated to Australia."

Farm practices

Lonsdale said farm management practices in Britain were very different from those in Australia, and the ecological relationships between plants and animals were profoundly different.

"We trudged around a few paddocks, and it's immediately obvious that the UK's cropping systems are much more intensive," he said. "The weeds persist on beneath the crop canopy, and in the hedgerows."

Some 76 per cent of Britain's landscape is farmland, so weed populations on farms are the basis of biodiversity conservation in the UK.

Where the top 20 weeds in Australian crops are all exotic species, only one major weed of British crops is an alien -- Veronica persica.

Because Australian invertebrates and birds are adapted to native ecosystems and plant species, farm weeds are not essential to their survival, whereas in Britain, weeds in crops and hedgerows provide habitat and food for native fauna.

This integration of farming and conservation is not practised to the same degree in Australia. Many farms preserve areas of remnant vegetation that are havens for wildlife, Australia has much more land that is not under cropping, with substantial areas of native vegetation harbouring native fauna.

"In our report we likened the British situation to Australian field crops being havens for native plant species like Sturt's Desert Pea and waratahs, and the native animals that associate with them," Lonsdale said.

It was significant that while the UK project found that GMHT sugar beet and canola adversely affected biodiversity, GMHT maize actually had beneficial effects.

"Non-GM maize was by far the worst crop for its impact on biodiversity," he said. The reason is that farmers growing conventional maize control weeds with the pre-emergence of the herbicide atrazine, which has residual action -- it strongly suppresses all weeds. (Atrazine is being phased out in Britain, because of its adverse environmental effects.)

In contrast, the post-emergence, knockdown herbicide glyphosate, or Roundup, used on GM feed maize allows more weeds to survive in the crop because it does not prevent weed seeds germinating, and lacks residual activity.

"GM maize is actually improvement on conventional maize in terms of maintaining weed diversity," Lonsdale said.

"This tells us you can't look at GM crops in isolation -- you have to test the impact of the entire management system.

"Looking at the way the issue has been reported in the UK media, it's too simplistic to say that if you plant a GM crop, species X will drop out. The way the farmer manages the crop is most powerful influence on the environment. To really understand the consequences of GM crops for biodiversity, you need to do large, landscape-scale trials."

Knock-on effects

The UK trials showed that, in general, weed populations were initially higher in GM crops sprayed with broad-spectrum post-emergence herbicides.

While broad-spectrum herbicides reduced seed numbers available to foraging birds, they increased the amount of decaying plant material available to decomposer-invertebrates like collembola (springtails), with potentially beneficial effects on nutrient recycling and soil fertility.

Predictions that changes in weed and insect biodiversity would have knock-on effects on bird numbers and diversity should be treated cautiously, Lonsdale said. Researchers had concluded it was not possible to obtain meaningful data on bird numbers from the field trials - the predictions were extrapolations from numerical models.

Lonsdale said another key finding, largely ignored by the UK and international media, was that the trials showed that the farmer's choice of crop was the most important determinant of its impact on biodiversity, irrespective of whether it was a GM or non-GM variety.

In other words, a farmer's decision to grow maize instead of sugar beet would have a much greater impact on weed density and diversity than any decision to grow non-GM or GM canola.

"It's not just an academic point," Lonsdale said.

Lonsdale said herbicide-tolerant canolas developed by conventional breeding already accounted for 70 per cent of Australia's canola crop -- triazine-tolerant (TT) varieties account for 60 per cent; the other 10 per cent are Clearfield varieties, which are tolerant to the Bayer herbicide Liberty Link.

"If we want to take a conservative approach in Australia, we should probably consider what is happening in these conventional herbicide-tolerant canola crops," he said.