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Assessing the environmental impact of GE crops: report on UK trials

24.oct.03, Food Safety Network backgrounder,

Given the continuing political and philosophical debate surrounding the use of genetic engineering (GE) in crop production, the October 16/03release of results from what’s been described "the biggest GM crop trials in the world"was sure to be met with a broad range of reactions and interpretations. Those involved with the trials were well aware of the potential risk. Both the Scientific Steering Committee charged with overseeing the trials and the editor of the scientific journal (Philosophical Transactions of the Royal Society) in which the results were published, issued stern cautions that the results should not be over-interpreted and could not be extrapolated beyond the studies’ very specific and limited objectives.
Caveats aside, reaction to the studies’ release has been swift, definitive and highly contradictory, including everything from calls for immediate bans on anything GE to assertions that GE crops ‘will save the planet." And each claims that the ‘proof’ provided by the UK studies supports their position. Although the studies, and the resulting conclusions, provide no such definitive answers, they do make a significant addition to the growing body of knowledge regarding the environmental implications not just of GE crops, but also of various farm management practices and even of agriculture itself.

...Although the studies, and the resulting conclusions, provide no such definitive answers, they do make a significant addition to the growing body of knowledge regarding the environmental implications not just of GE crops, but also of various farm management practices and even of agriculture itself.

Purpose of the Studies
The environmental impact of agricultural production, in general terms and more specifically on wildlife populations, is an issue of growing concern in many jurisdictions. As agricultural production has increased in efficiency, bringing the benefits of better food, improved yields and lower production costs, the variety and abundance of weeds in and around productive agricultural lands has declined. Despite the benefits, there is concern in some quarters that more efficient agricultural production has resulted in the loss of food sources and habitats for wildlife.
Although the movement towards increased efficiency has advanced steadily since the 1960s, the advent of genetically engineered (GE) crops has brought new questions about the broad-ranging environmental impacts of food production, including potential effects on wildlife populations.
As part of its effort to develop sound overall policies on the production and use of GE crops, the UK government appointed an independent Scientific Steering Committee in May, 1999, to oversee ecological studies that would assess the impact of the production of genetically engineered herbicide tolerant crops on farmland wildlife.
Field-scale evaluations of three herbicide-tolerant genetically engineered crops – maize [corn], beet and spring oilseed rape [canola] – were conducted over a three-year period. Trials on a fourth crop – winter oilseed rape – have recently been concluded and will be the subject of a report expected in mid-2004.
The trials involved the production of the GE herbicide tolerant varieties and their conventionally produced equivalents. Crops were managed by standard protocols, with researchers conducting comparative studies to assess the effects of the management of the GE crops on ecological groups such as insects and weeds.
In total, the study involved 273 trial fields in England, Scotland and Wales, at a total cost of close to ?6 million (over $13 million Cdn).
The chosen crop varieties, while not yet released for commercial production in the UK, were approved for use in the trials by the Advisory Committee on GM Releases to the Environment (ACRE), the UK government’s statutory advisory committee. ACRE believed that use of these crops would pose no threat to human health or the environment. Crops produced in the trial were destroyed after harvest.
The studies, overseen by the Scientific Steering Committee and conducted by a consortium of independent contractors working in conjunction with UK farmers, were designed to answer the question of how growing herbicide tolerant GE crops might affect farmland wildlife as compared to growing non-GE, non-herbicide tolerant varieties of the same crop. Implications of the study will be reviewed by the UK and other EU member states for consideration on current and pending applications for GE crop approvals.

Each of the Field Scale Evaluation trials studied – and ultimately rejected – the hypothesis that the abundance and diversity of wildlife is unaffected by the management of herbicide tolerant GE crops as compared to their conventional alternatives. In each case, researchers found differences in wildlife populations between the GE crop fields and the conventional crop fields.
Researchers stressed that the differences resulted from the manner in which the crops were managed, not from the fact that they were developed through GE technologies: herbicide tolerant crops give farmers new weed control options that ultimately affect wildlife populations. They suggested that the differences found in wildlife populations between the GE crops and the conventional crops could be similar to those that would occur when farmers changed from growing one crop to another. Farm management decisions – whether in GE or conventional crop production – will inevitably have some impact on wildlife populations. To date, that impact has not been comprehensively assessed.
In general, researchers found that insect populations and weed populations were closely related - the more weeds in a field, the more insects there were.
In maize [corn] crops, the GE herbicide tolerant variety provided better refuge for wildlife than the conventional variety. Researchers found that there were more weeds in and around the herbicide tolerant GE maize crops, more butterflies and bees at certain times of the year, and more weed seeds, which can be important in the diets of some birds. Most farmers growing the conventional maize crop used the herbicide atrazine before or just after the weeds started to grow. This herbicide prevents most weed seeds from terminating and developing, thus reducing the potential of the fields as foraging grounds for insects. In the GE herbicide tolerant maize, herbicide is not applied until much later in the crop’s development, thus allowing for the growth and development of weeds in the earlier stages.
In beet and rapeseed [canola] crops, fields planted with GE herbicide tolerant varieties had fewer weeds and fewer weed seeds than fields planted with conventional varieties. Researchers believe that the broad-spectrum herbicides used on these crops were more effective at killing weeds than the specific herbicides used on conventional crops. There were fewer bees and butterflies in such fields because there were fewer weeds available to provide food and cover. Some species of soil insects that feed on decaying and dead weeds were more abundant in the GE crop fields. Although farmers producing conventional beet and spring rapeseed crops also often used pre-emergence herbicides to prevent weed development and growth, these herbicides provided less effective control than the atrazine used by the maize farmers.

Next Steps
Following the October 16, publication of the results in Philosophical Transactions, the study’s Scientific Steering Committee will hold public meetings to present findings and answer questions. ACRE – the UK government’s statutory advisory committee on the release of GMOs – will review the findings and provide further advice to governments on potential regulatory implications. A report on the coexistence of GE and non-GE crops is also soon to be published. Along with this study and the forthcoming report on the production of GE herbicide tolerant winter oilseed rape, the work will provide further areas for consideration in the environmental assessment of new crop varieties. Results will also be shared with, and considered by, other EU member states.

The comprehensive field-scale evaluations conducted in the UK successfully achieved their goal, that is, “to examine the effects of the management of selected GE crops on specified species within distinct geographical confines and time limits.” As such, they provide one piece of the puzzle in determining the safety and applicability of genetically engineered crops in agricultural production systems.
Researchers point out that management protocols, not the manner in which new crops are developed, are the determining factor in wildlife abundance and diversity.
Although researchers point out that the production of GE crops can result in broader environmental and production benefits, delineating such benefits was not within the scope of the study.
As a result, considerations cited by farmers who choose GE crops in countries where such crops are approved – including higher yields, reduced pesticide use (in GE pest-resistant crops), lower natural toxin levels and improved production efficiencies – could not be weighed against the studies’ findings. The responsibility for such risk-benefit analyses and decisions must lie with regulators, not scientists.


Baldock: UK GM trials prove caution way to go. United Future Media Release. 17 October 2003.

British Broadcasting Corporation (BBC). GM tests show danger to wildlife. 16 October 2003.

“Case not proven.” Leader. The Guardian. 17 October 2003.,3604,1064722,00.html

Department for Environment, Food and Rural Affairs. “Farm-scale Evaluation Results: Important New Evidence on GM Crops.” News release, 16 October 2003.

Department for Environment, Food and Rural Affairs. “Background Note for Journalists on the Farm Scale Evaluations of GM Crops: Publication of the Results and the Way Ahead.” 13 October 2003.

Dickson, David. “No easy answers on GM crops.” Scidev.Net. 20 October 2003 fuseaction=readEditorials&itemid=92&language=1

The Farm-Scale Evaluations of spring-sown genetically modified crops. Philosophical Transactions: Biological Sciences Series B Volume 358 Issue 1439 29 November 2003.

Gallen, Angela. Bird charity joins call for ban on GM crops. Dorset Echo. 17 October 2003.

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Major British studies find some GM crops harm wildlife. ABC News Online. 16 October 2003.

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Scientific Steering Committee for the GM crop farm-scale evaluations. “Final Advice to Ministers.” 16 October 2003.

“Value in a GM Crop”. Editorial. Globe and Mail. 20 October 2003.

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