Wednesday, 24 March 2004

GM Crops and Birds

Among the trustees of the WLT we are fortunate to have Professor Renton Righelato, who is not only a keen naturalist, but a professional biologist with particular expertise in food technology. I am very please to include in this blog some of his comments on the current debate over GM crops. I think he adds a very important perspective to a complex and controversial issue:

GM Crops and Birds

As a biologist engaged in both nature conservation and food science, I sometimes feel beleaguered, faced with a plethora of unscientific arguments against GM and disingenuous justifications put forward by the supporters of the technology. I was involved in developing the current regulatory framework for safety evaluation of GM and other "novel foods" and I am confident that the scrutiny given to these foods ensures that they are at least as nutritious and safe to eat as their non-GM counterpart. I am less confident that we are assessing possible environmental impacts effectively.

The GM crops currently approved in Europe have been modified to be resistant to broad spectrum herbicides or to make a protein that kills several classes of insect pests. They make crops cheaper to grow by reducing the number of applications of chemicals to control weeds or insects. Depending on exactly how the crops are grown and treated with chemicals, they could be harmful or helpful to wildlife. In February 2004, the British Ornithologists' Union held a conference at the Royal Society to explore the implications for farmland birds. This is important because the crashing populations of many farmland bird species over the last 25 years have been the most obvious indicator of the damage to biodiversity resulting from intensification of farming.

To assess the impact of growing some of these crops, the UK government carried out farm-scale evaluations between 2000 and 2002. The trials were carried out with genetically modified, herbicide-resistant sugar beet, fodder beet, spring oilseed rape and fodder maize over three years, each at twenty or more sites. The GM planted plots were compared with conventional varieties and management practice in adjacent plots in the same fields. Throughout each year, the range of weed species, the seed produced, the seed bank (the seed accumulating in the soil) and the insects and other invertebrates in the plots were monitored – these represent the food that might be available to mammals and birds.

  • In sugar beet and oilseed rape, weed mass and seed rain in the GM plots were less than a third than the conventional plots.
  • With GM maize, there was almost twice as much weed mass and seed rain compared with conventional maize
  • Unsurprisingly, the invertebrates were affected in the same way as the weeds on which they rely.

Based on these results, the government has announced its intention to approve the use of the herbicide tolerant maize but not the beet or oilseed rape. But the use GM maize is unlikely to have a significant beneficial effect on bird populations, because both it and conventional maize are poor for weeds and their seeds. Moreover, the herbicide used in the conventional maize treatment, the persistent soil herbicide, atrazine, is shortly to be banned and alternative management regimes may well prove less damaging.

Genetic modification of crops may well have a role to play in ameliorating the loss of biodiversity caused by intensive farming, but not from the crops and management regimes so far tested in the UK.

The main take home message for me was that the differences in food available to birds in these trials was trivial compared with the ten fold or more decreases that have come about over the last 25 years from winter sowing, herbicide and pesticide use, more efficient harvesting and more complete use of the land for the crop. So, any substantive change in agricultural practice should be subject to as thorough an environmental impact assessment as these GM crops.

Had this principle been applied in the "green (a somewhat ironic description now!) revolution", we might have avoided the desecration of much of our landscape, the loss of many plant and insect habitats and the elimination of winter feeding for much of our wildlife –the legacy of our headlong rush into agricultural intensification we now struggle to ameliorate.

Renton Righelato

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