Canadian ‘super weeds’ undermine European GM safeguards

A UK government agency has expressed deep concern that the European Community’s recently proposed GM seed threshold is too high to prevent the creation of ‘super’ GMO weeds that are herbicide-tolerant, and that current separation distances for GM crops need to be revised upwards.


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English Nature is warning of the increased environmental risks associated with the accumulation, or ‘stacking’ of modified genes from separate GM varieties in plants that grow from seed spilled at harvest, known as volunteer plants. This follows the publication of a UK government funded study led by the agency – of GM herbicide-tolerant oilseed rape crops in Canada – which confirms fears raised two years ago over the discovery of triple-tolerant oilseed rape. In Canada farmers are already resorting to more intensive use of herbicides to eradicate these so-called ‘super weeds’ from field margins and uncropped habitats, which can be important refuges for wildlife.

English Nature is now particularly concerned that the recent EC proposed 0.7% GM threshold for non-GM crop seed, might be a recipe for gene stacking. GM plants from a seed batch could be made up of several varieties that would inevitably hybridise, giving ‘volunteer’ plants in the next season with multiple GM traits.

Also, it has highlighted the difficulty in policing seed batches. This follows the opinion of the EC Scientific Committee on Plants, which has already advised that the proposed thresholds will be difficult, if not impossible, to achieve, particularly as the global area of GM crops continues to grow.

The study also indicated that the Canadian system of voluntary guidelines advising farmers to leave a separation distance of 175 metres between different GM varieties seems to have broken down, and ‘gene stacking’ is now widespread in Canada. The UK’s GM industry group, SCIMAC (Supply Chain Initiative for Modified Agricultural Crops) code of practice recommends a 50 metre separation distance for GM oilseed rape.

Dr Brian Johnson, English Nature’s biotechnology advisor said “Our report shows that the SCIMAC code is probably inadequate to prevent gene stacking happening in Britain, if these crops were commercialised. The consequences for farmers could be that volunteer crops would be harder to control and they might have to use different, and more environmentally damaging, herbicides to control them.”

English Nature has been pressing the GM industry to explain how to deal with these issues before GM crops are released widely. The Agency says it will be working with DEFRA and the Advisory Committee on Releases to the Environment (ACRE), to ensure that risks from possible gene stacking are properly addressed, to avoid the mistakes that have been made in Canada.

This latest GM alert follows two others in recent days focussing on food safety issues, from the French food agency and the Royal Society. While not doubting the safety of foods made from GM ingredients, a Royal Society report warned that safety assessments should be improved before a greater variety of GM-based foods are declared fit for human consumption. The report called for a tightening of regulations for all novel foods, particularly with respect to allergy testing and the nutritional content of infant formulae.

Also recommended was that the methods for comparing GM food with conventional counterparts, by applying the principle of ‘substantial equivalence’, should be made more explicit and objective during safety assessments, and harmonised across Europe.

Professor Jim Smith, who chaired the working group, said: “The rather piecemeal approach to the regulation of GM foods in the UK and EU in general, means that there may be some important gaps and inconsistencies… But the legislation must not be so restrictive that it removes any incentive for introducing new food products that are potentially beneficial to society.”

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