Science - Based Risk Assessment for the Approval and Use of Plants in Agricultural and Other Environments

T he use of plants as crops to produce food, fiber, and other products has an amazing record of environmental safety. The greatest risk with any plant deliberately introduced into a new environment is its potential for inva-siveness beyond the planted area—to become a weed—but even here crop plants have an outstanding record of safety. Crop plants typically must be managed as " weedy " volunteers after harvest, and some varieties of crop plants are more prone than others to carry over in the field after harvest. I am not aware, however, of a crop plant having become an invasive weed because of plant breeding. This remarkable record of safety for crop plants would indicate that either (1) the risks to the environment presented by crop plants are low; (2) the extensive field testing prior to commercial use and the institutional assessments and decisions on which plants or varieties to grow as crops have been sound; and/or (3) the management practices in place have been adequate to mitigate any risks inherent with plants. Of the " risks " that have been associated with plant-based agriculture, virtually all are the consequence of the management practices needed to grow crop plants and keep them healthy. The environmental risks include soil erosion because of tillage used to form a seedbed and control weeds, nitrates left unused in the soil because of overfertilization (or underutilization because of disease), nontarget effects of pesticides on beneficial insects, and smoke from burning crop residue. These are just some of the more important environmental impacts associated with the growing of crops. Genetic modification of crop plants is unquestionably the best route to mitigation of these risks, but must be accomplished without introducing new risks. In spite of the safety record, there is public concern worldwide that plants with genes introduced from outside their normal range of sexual com-patibility—the so-called " genetically improved " plants (GIs)—might present new risks to the environment. Some of the more frequent claims expressed in the popular press or on the many websites established for the express purpose of raising concerns, include: virus-derived genes used as a source of virus resistance in crop plants will lead to new viruses with potential to kill native plants; the use of genes from Bacillus thuringiensis (Bt) as a source of resistance to insect pests will lead to super pests; the antibiotic-resistance genes used as selectable markers will …