The six-year programme of monitoring several GM oilseed rape crops ended in 2000. While several of its findings have previously been publicised, the final report drums home the message that with a promiscuous and widely grown crop like oilseed rape it is inevitable that modified genes will be transferred to conventional rape or related crops or weeds through pollen transfer by insects or wind.
The study by the National Institute of Agricultural Botany found "a number of unpredictable factors that may influence levels of outcrossing in agricultural systems." In two GM crops in Lincolnshire and Oxfordshire, unexpectedly high cross-pollination levels into conventional crops were observed up to 200 metres away.
The researchers propose several factors to explain this, including disturbance of air currents by a copse in the middle of a field, or impurities in the conventional crop which made it more susceptible to cross-pollination. More bizarre possibilities were contamination of the supposed conventional crop seed by GM material prior to import, and even accidental transfer of GM material by anti-GM demonstrators who destroyed much of the Oxfordshire site.
The study found that "varietal association" varieties of oilseed rape, which contain some male sterile plants and therefore generate less pollen of their own, are much more susceptible to contamination. Separation distances for these may need to be reviewed, it recommends.
The report concludes that "more data from large-scale plantings are needed to assess patterns of gene flow between varieties of oilseed rape under agricultural conditions." These should include an assessment of the influence of factors such as environmental conditions, geographical locations and cropping patterns.
In a recommendation likely to be central to the current debate about the possible commercialisation of GM crops in the UK, it adds: "Only when such studies have been carried out will it be possible to establish the most effective isolation distances between transgenic oilseed rape crops and conventional crops in order to keep contamination within defined limits."
The study also pinpointed practices which tend to increase cross-contamination risks. These include inadequate cleaning of farm machinery such as combine harvesters and mixing of seed during transport to processing plants. Such practices, it concludes, mean that it is "not practicable" to prevent contamination of conventional seed sources by GM varieties.
The study established for the first time that oilseed rape crossbreeds with weedy wild turnip populations in England, making transfer of GM genes likely. The extent of this will depend on local circumstances and cropping practices. Perversely, the researchers suggest, a more effective weed control regime leaving fewer wild turnips in a field may increase the risk of gene transfer due to competitive advantage. Further studies are needed, they conclude.
The Advisory Committee on Releases to the Environment published a brief opinion of the NIAB research on Christmas Eve, saying it was consistent with its own risk assessment of the release of GM rape.
ACRE said it "has always assumed some gene flow will occur and that this does not in itself constitute a risk to human health and the environment." It considered that "the extent of gene flow observed in the monitoring between GM oilseed rape and adjacent crops, feral oilseed rape and wild relatives was entirely within expectations."
Environmental groups believe that ACRE has made up its mind that GM crops will be commercialised and that the consequent risks may have to be minimised but will have to be borne. Friends of the Earth accused the Committee of playing down the significance of the findings.
GM campaigner Pete Riley accused ACRE of being "more interested in defending their earlier advice than listening to the science. Such complacency is completely unacceptable." He argues: "The report shows there are still big holes in the science of cross-pollination....Surely the only sensible course is to abandon GM and instead help British farmers get off the agrochemical treadmill by investing in sustainable farming."
Such reactions to NIAB's report neatly encapsulate the dilemma facing the Government as it enters a critical year of decision-making on the costs and benefits of commercialising GM crops.