Environmental Effects

One of the most commonly expressed concerns about possible envi­ronmental effects of GM foods is that genes inserted into a modified plant might escape into the surrounding environment and be taken up by wild relatives of the engineered crop plant. Such a possibility exists, some experts say, because of the close taxonomic relationship among some crops plants and weedy relatives. Sunflowers, sorghum, canola, and squash are commonly cited examples of crop plants that have weedy relatives capable of cross-breeding with them. If such interbreeding did happen, weeds would develop the same resistance to herbicides that had been bred into the crop plant, resulting in "superweeds" that might make control efforts even more difficult than they are now. A possible consequence of such gene transfers is that farmers would have to use even stronger pesticides—and more of them—than they use today, increasing the overall risk to the en­vironment.

A study conducted by the environmental group English Nature in late 2001 bears out this risk. The group's research showed that herbicide-resistant genes inserted into certain rapeseed oil crops in Canada had escaped into surrounding areas, resulting in the growth of weeds that also contained the genes. According to Brian Johnson, the organization's adviser for biotechnology, the conse­quences of using modified seeds could be "that volunteer crops would be harder to control and [farmers] might have to use dif­ferent, and more environmentally damaging, herbicides to control them."

Chemical companies that have developed such products pres­ent different views. For example, representatives from the German chemical company AgrEvo (Hoechst Schering AgrEvo GmbH) have said, for example, that pollen from engineered plants is unlikely to spread more than about 30 feet (10 m) from the parent plant. If gene transmission does occur, they say, the weeds affected will not become superweeds but will inherit a resistance to only a single her­bicide, the one for which the engineered crop plant was developed. Besides, they argue, such events do not really change the problem facing farmers, since weeds need to be controlled anyway, no matter how that control is achieved.

One of the strongest arguments for the use of GM foods is that they may lead to substantial reductions in the amount of pesticides used in agriculture. If a gene can be inserted into a crop plant that is lethal to some pest, then a pesticide does not need to be sprayed on that crop. And the overuse of pesticides in agriculture throughout the world has long been one of the most serious concerns among environmentalists about the way in which crops are grown today. A study reported by Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) in August 2003, for ex­ample, showed that cotton farmers in that country had been able to reduce their use of pesticides by 50 percent through the use of a bioengineered cotton called Bollgard II, developed by Monsanto. Bollgard II was designed to provide resistance to some of the most serious pests that attack cotton crops, including bollworms, army-worms, and loopers.

Critics of GM foods are not convinced by this argument. They point out that the use of an engineered pesticide, such as Bollgard II, eventually results in the rise of new members of a pest population that are stronger and more resistant to the pesticide being used. As a result, larger amounts of the pesticide are needed to keep the pest under control during each growing season. Proponents of GM pest control counter that this pattern is true any time a pesticide is used, whether it is sprayed on a plant or engineered into the plant's genome. With genetic engineering, at least other risks of pesticide use (such as the risks to workers who have to handle and dispense the chemical) are reduced or eliminated.

In the controversy over GM foods, a handful of research stud­ies have been published that have raised significant concerns about such foods and aroused widespread public opposition to the engi­neering of foods. One such study was reported in 1999 by a team of researchers from Cornell University led by John Losey. Losey's team fed monarch butterfly caterpillars the leaves of a milkweed plant that had been dusted with pollen from an engineered corn devel­oped by the Swiss chemical company Novartis. Researchers found that nearly half of the caterpillars died and those that did survive did not develop properly. Almost as soon as the study was published in the prestigious English scientific journal Nature, both consumer groups and scientists not involved in the study began to denounce GM plants. Two of the United Kingdom's largest supermarket chains, Sainsbury's and Iceland, announced that they were removing all GM foods from their shelves.

Other scientists quickly criticized this knee-jerk reaction. They pointed out that Losey's study provided only preliminary infor­mation and that, by comparison, far more monarch butterflies are killed by truck traffic in agricultural areas and as a result of habi­tat destruction in Mexico than would be destroyed by engineered corn. In November 2000 at a conference in Chicago, entomologists met to analyze the research on engineered corn and monarch but­terflies in more detail. They came to the general conclusion that there was no significant difference in the survival rates of monarch butterflies in areas where GM corn had been planted and where it was absent. As one attendee noted, "If there are any differences, they are not very profound." Another study reported by researchers at the University of Maryland concluded that monarch butterflies actually have a much better survival rate in the presence of GM crops than in the presence of crops that have been sprayed with pesticide.

Micropropagation. Cereal plants being grown in test tubes from tissue cultures. (Rosenfeld Images Ltd./Photo Researchers, Inc.)

Thus far, the question of possible environmental effects from the use of GM crops has not been resolved. Reasonable arguments to worry about such effects have been set forward. But thus far little scientific evidence is available to support such concerns.