A review of scientific evidence on the environmental impacts of growing genetically modified herbicide tolerant crops relevant to the UK

Herbicide tolerant (HT) crops are not a new phenomenon – in fact, all crops are to some extent tolerant to herbicides. Many herbicides are dose-specific for particular plant groups, for example grasses, and these can be used on broad-leaved crops like potatoes and oilseed rape without causing unacceptable harm. This is the basis for most current agricultural practice in developed countries. Genetic modification, however, has enabled crops to be made resistant to concentrations of ‘broad-spectrum’ herbicides that have a mode of action that is lethal to all conventional crops and wild plants. Examples of broadspectrum herbicides to which GM plants have been made resistant are glyphosate and glufosinate-ammonium. These herbicides, particularly glyphosate, are already regularly used by farmers in the UK to ‘clean up’ weedy stubbles and to desiccate crops such as potatoes and oilseed rape before harvest.