I am contributing a short piece on the environmental impact of GM plants in the context of the impact of conventional agriculture. I am a full-time scientist with 20 years of postdoctoral research experience in soil microbiology and ecology, including plant-microbe-soil interactions, at Rothamsted Research, an Institute sponsored by the BBSRC. I am a member of ACRE and I chair the subgroup on Soil Ecology - this contribution includes a link to our interim report, published on the Defra website.

Penny Hirsch
Dr Penny R. Hirsch
Agriculture and the Environment Division
Rothamsted Research
Harpenden, Herts AL5 2JQ, UK

Environmental impact of agriculture

Agriculture has had a major effect on the environment over millennia. Cultivation techniques such as ploughing and crop rotation, used to control weeds, suppress pests and diseases and maintain soil fertility, have been used in Europe for centuries and are well-established facets of conventional agriculture. Most crops grown are not native to the UK, some can "escape" from cultivated land and become established outside the agricultural environment, and many can cause weed problems due to seeds surviving in subsequent crops. However, most are unable to survive without the intervention of farmers to cultivate the soil, suppress weeds that would otherwise out-compete them, and provide fertilisers and irrigation where needed. Conventional plant breeding programmes produce lines that differ in many traits including disease susceptibility, and nutrient composition for food and fodder. Inadvertent changes in properties that might impact humans and the natural environment: increased levels of natural toxins, or improved seed survival, should be considered with any new line.

GM plants could have additional effects in several ways.

• Herbicide tolerant crops are subject to different regimes compared to conventional crops, allowing less herbicide to be used, later in the crop cycle. This may influence several factors; a herbicide tolerant crop selected and bred without GM would have a similar impact.
• Plants with novel GM traits e.g. the insecticidal Bt toxin, may provide new selective pressures on target and non-target insect pest populations. Effects on harmful and beneficial insect populations and insectivores may be different from that of conventional insecticides and should be considered in comparison.
• Future GM technology may allow cultivation of plant species currently unable to grow in the UK. Impacts will be similar to those due to the introduction of any novel plant species; the potential for harm such as becoming an invasive weed should be carefully considered.

The Advisory Committee of Releases to the Environment (ACRE) considers many factors, including those outlined above, when discussing the potential release of GM plants. A recent report by the subgroup on soil ecology, that considers potential GM crop impacts in the context of conventional agricultural practices, can be found at www.defra.gov.uk/environment/acre/soilecology/acre_soilecology_interim.pdf. Perhaps the introduction of novel crops, new varieties of existing crops, and also ornamental plants, should be subject to similar careful consideration. The main problems caused by invasive plants in the UK have been due to garden escapes of exotic ornamental plants, rather than agricultural crops.

Summary of key points

Conventional agriculture was developed to exploit the "natural" environment for crop production and consequently has significant impacts. GM crops may require different practices but their impact is potentially similar or less.