The National Academy of Sciences published a major report today (February 21) on the environmental effects of genetically modified plants. Deborah Letourneau, a professor of environmental studies at the University of California, Santa Cruz, and a leading authority on this controversial new technology, contributed to the NAS report and coedited another just-published volume on genetically engineered organisms.
As an expert on the academy's 12-member National Research Council Sub-Committee on Environmental Consequences of Genetically Modified Plants, Letourneau contributed to the new book, Environmental Effects of Transgenic Plants: The Scope and Adequacy of Regulation (Washington, D.C.: National Academy Press, 2002). Letourneau's focus was to examine how well the U.S. government is regulating transgenic crops to avoid any negative effects.
In the other new book, Genetically Engineered Organisms: Assessing Environmental and Human Health Effects (Boca Raton, Fla.: CRC Press, 2002), Letourneau and coeditor Beth Burrows, president and director of the Edmonds Institute in Edmonds, Washington, present worrisome gaps in knowledge about the long-term effects of genetic engineering and call for more extensive and rigorous examination of the potential impacts of genetically modified plants and other organisms. Contributions by prominent researchers showcase the many unanswered questions that weaken assessments of biosafety.
"There is a disjuncture between the people creating the products of genetic engineering and the knowledge of evolutionary biologists and ecologists," said Letourneau. "Like many ecologists, I've been trying to inform the public about the effectiveness and possible environmental and human-health impacts of genetically engineered organisms."
For several years, Letourneau has put aside her own work on insect-plant interactions to lead the call for more research on genetic modification of plants and other organisms. Letourneau is hopeful that more research will stimulate a fuller evaluation of the benefits and risks of genetic modification.
Among the issues discussed in Genetically Engineered Organisms are:
- New research that indicates how potentially misleading it can be to use average distances to estimate hybridization rates between transgenic crops and their wild relatives. "We're underestimating possible risk by concentrating on the average hybridization distances," said Letourneau.
- New evidence suggests that genetically modified, or transgenic, plants might hybridize at higher rates than "equivalent" nontransgenic plants that were conventionally bred for herbicide resistance. The U.S. Department of Agriculture seeks "equivalent" products, but these findings point out a significant difference between transgenic and nontransgenic plants.
- Unintended consequences of genetic modification could include local extinction of some species. For example, transgenic salmon that are made to grow faster by expression of a growth-hormone gene might be more attractive to predators, and the species could be vulnerable to a population crash.
- More needs to be known about the "driver mechanisms" of genetically modified organisms before the technology is widely introduced. Introduction of a transgenic malaria-resistant mosquito in an area plagued by an epidemic, for example, would help tremendously in the short run but could have potentially devastating unintended public-health consequences if human immunity levels fall, as would be expected, and the driver mechanism of the transgenic mosquito subsequently fails.
Despite such broad gaps in current knowledge, commercial application of genetically engineered plants has become widespread in the United States and other countries. According to Letourneau, transgenic corn accounts for about 26 percent of worldwide corn production. Transgenic corn contains the toxin of the Bacillus thuringiensis (Bt) soil bacterium, which disrupts the digestive system of a caterpillar. Cotton and potatoes have also been modified to produce Bt toxin, while other crops, such as soybeans, have been modified to resist the herbicide Roundup.
Marketed to farmers as tools to ensure higher yields, transgenic crops are being touted as a breakthrough strategy to help feed the world's fast-growing population. But ecologists worry about potential unintended effects of genetic engineering, such as the nontarget impact Bt corn pollen was found to have on Monarch butterflies. In 1999, Cornell University researchers reported Monarch caterpillars that were fed milkweed dusted with pollen from Bt corn grew more slowly and suffered higher mortality rates than those fed milkweed dusted by pollen from untransformed corn or milkweed free of pollen. The wider implications of such nontarget effects are discussed by the Cornell researchers in a chapter of the new book.
Regulatory agencies and companies developing genetically modified organisms have a responsibility to be accountable to the public, said Letourneau, but companies are held to a lower research standard than are peer-reviewed academic researchers. In addition, industry findings are often protected as proprietary information, which makes it impossible for Letourneau and other outside scientists to evaluate the quality and scope of in-house research.
"U.S. regulatory agencies typically rely almost entirely on data submitted by the companies themselves," said Letourneau. "Even when I've been asked by the U.S. Department of Agriculture to review the findings, I can't get access to them. Companies may be doing a good job, but it's hard to tell."
"People don't know the in's and out's of genetic engineering, but they remember the Ford Pinto," she said. "Credibility is really important, and companies and regulatory agencies need to build it."
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Editor's Note: Deborah Letourneau is available for interviews. She may be reached by calling (831) 459-2860 or sending e-mail to dletour@cats.ucsc.edu.
