Report Backs Modified Crops

The introduction of genetically modified crops has had a positive impact on farm sustainability, according to a new report by the National Research Council (NRC). But the evolution of herbicide-resistant weeds could erase the effectiveness of the most common engineered crop traits, the council warns.

“It is important to emphasize that genetically engineered crops—specifically soy, corn, and cotton—have provided multiple benefits to farmers,” said David E. Ervin, chair of the report committee, at a panel discussion in Washington, D.C., this week to introduce the findings. Ervin is a professor of environmental management at Portland State University.

The report compared farms planted with genetically engineered crops with those following conventional agricultural practices. It found that farmers who planted seeds engineered for resistance to glyphosate applied that single herbicide instead of more toxic herbicides. They were also more likely to use glyphosate in place of tilling as a means of managing weeds. Low- or no-till farming reduces soil loss from erosion and can improve soil quality and moisture retention. The report also pointed out that less tilling helps prevent runoff from fields.

In addition, because farmers have adopted seeds engineered with the Bacillus thuringiensis (Bt) toxin for insect resistance, the application of insecticides has decreased, the panel said. The broad-spectrum insecticides commonly used against pests also kill beneficial insects such as honeybees and the pests’ natural enemies.

Critics of genetic engineering took issue with the panel’s generally positive findings. “In the end, NRC makes too much of short-term benefits of certain genetically engineered crops and fails to appreciate the inherent unsustainability of the pesticide-promoting technologies,” said Andrew Kimbrell, executive director of the Center for Food Safety.

NRC also investigated the economic effects of farmers’ use of genetically engineered seeds. It found that herbicide-resistant seeds did not substantially increase yields but did decrease the cost of production through more cost-effective weed control. And in places where insects can cause high losses, seeds with the Bt trait can preserve yields and save money on insecticides.

The panel found that the biggest risk in using engineered seeds is the possible evolution of resistant pests. Although the panel did not find evidence of significant insect resistance to the Bt toxin, eight or nine weed species have evolved resistance to glyphosate in parts of the U.S. In his remarks, Ervin said that researchers must “document the emerging weed problem and develop long-term strategies.” He warned, “The problem is growing; it’s real, and it’s going to get worse.”