Introduction: Keeping Watch on Genetically Modified Crops
In May 1999, researchers at Cornell University made headlines with a report about genetically modified corn plants and monarch butterflies. The corn was of a type that had been modified to produce an insecticide known as Bt toxin to protect it from the depredations of the European corn borer. By virtue of this modification, Bt toxin is also produced in the pollen of the corn plants. Cornell scientists found that when monarch caterpillars were raised on leaves dusted with Bt-containing pollen, many of them died. Milkweed plants, the only food source for monarch caterpillars, often grow along the edges of cornfields, and the researchers speculated that genetically engineered corn might pose a danger to the beloved butterflies.
As this is written, there is still no proof that the caterpillars are or are not at risk. A number of ameliorating factors could intervene, such as removal of much of the pollen from leaves by wind and rain or the caterpillars' avoidance of the most heavily dusted leaves. Whatever its resolution, the episode has underscored two important points about genetically engineered plants. First, the introduction of transgenic crops or, indeed, of any new crop into an area can have unforeseen consequences for the surrounding ecosystem. Second, the public is particularly sensitive to damage or potential damage caused by genetically modified plants, as opposed to damage caused by plants created by traditional breeding methods.
It was more than 13 years ago that a National Academy of Sciences white paper examined the emerging field of genetic engineering and
offered a set of principles to serve as a starting point for the analysis of transgenic organisms and their possible effects on the environment. First, the paper concluded, the act of creating transgenic organisms itself carries no special threat. Second, the risks associated with placing transgenic organisms into an environment are of the same type as the risks associated with releasing any new organism—one brought in from another location, for example, or one that has been created by conventional breeding—into an environment. Third, to assess the risks posed by introducing a transgenic organism into an environment, one need consider only the characteristics of the organism and of the environment, not how the organism was produced. However, at the time these principles were drafted, there were no commercial releases of genetically modified organisms.
In the years since that white paper appeared, genetic engineering of plants has gone from a new and largely untested technique to common agricultural practice. Although genetically modified plants did not become commercially available in the United States until 1995, they now account for a major portion of the crops that American farmers plant each year. In 2000, some 70 million acres of transgenic crops were grown in the United States, including 25% of all corn, 54% of soybeans, and 61% of cotton (Reference: USDA's National Agricultural Statistics Service). Of those acres, 30 million were devoted to plants that have been genetically engineered to produce the Bt toxin, and much of the remaining area was planted with crops that have been engineered to resist wide-spectrum herbicides, such as Round-Up (manufactured by Monsanto). A field of such herbicide-resistant plants can be sprayed with the herbicide in question to kill all weeds and leave only the crop plants alive. Other, less widespread transgenic crops were also grown, such as plants that have been given resistance to particular viruses by having a gene from the virus inserted into their DNA. Although the current disfavor with genetically engineered plants in the European Union might slow their spread among American farmers, many of whom sell to Europe, it seems likely that transgenic crops will remain an important component of American agriculture.
As transgenic crops have become more widespread, so have concerns about their possible risks to human health or to the environment. Some people believe that the risks are no greater than those posed by traditional crops and expect the benefits of transgenic crops to outweigh any disadvantages. Others worry that the risks have not been properly assessed and that the crops will pose dangers that will not become clear until it is too late.
One of the natural responses to the controversy is to gather more information about genetically engineered plants and their effects. In April 2000, when a committee of the National Research Council released a report
on transgenic plants and regulation, Genetically Modified Pest-Protected Plants: Science and Regulation (National Academy Press, Washington, DC), many of the recommendations were for research to determine more precisely the potential of such crops to harm either human health or the environment. Although the report was careful to say that there is no strict dichotomy between the health and environmental risks that might be posed by transgenic and conventional pest-protected plants, the committee acknowledged that much is still not known about transgenic crops. 1
Against that backdrop, on July 13-14, 2000, the National Research Council held a workshop on Ecological Monitoring of Genetically Modified Crops. As the title suggests, the workshop specifically excluded monitoring aimed at detecting effects on human health. Its focus was on monitoring for effects that genetically modified crops might have on the surrounding ecosystems, including plants, animals, and microorganisms. The purpose was to lay out the issues surrounding such monitoring, to describe what was known, and to identify what needed further attention.
After 2 days of presentations and discussion, numerous workshop participants expressed the opinion that ecological monitoring of genetically engineered crops is warranted, and they discussed in detail many of the scientific and policy issues that will influence the success or failure of such monitoring. The following is a summary and synthesis of the presentations and discussions in that workshop.
1 The specific focus of the report was crops, such as Bt corn, that have been modified to resist pests, but it noted that many of its conclusions and recommendations applied to other types of genetically modified crops.