Monarch Butterflies and Bt Corn: How Big Is the Threat?

In the spring of 1999, researchers at Cornell University found that monarch caterpillars died in the laboratory after eating pollen from genetically engineered corn. The corn had been given a gene from the Bacillus thuringiensis bacterium (Bt) that produced a toxin that killed the European corn borer pest, an expensive threat to corn. Finding out just how much of a risk the biotech corn poses to wild monarch butterflies is the subject of ongoing studies and intense debate.

First, researchers had to set out and find whether monarch caterpillars would encounter Bt corn pollen. They found that most toxic pollen is shed within the cornfield, not outside it, which seemed to be good news for the monarchs. However, in the summer of 2000 ecologists at the University of Minnesota found that monarch caterpillars may live on milkweed in cornfields and therefore be at risk. Then other researchers failed to find a difference in survival rates for monarch caterpillars in normal cornfields and in Bt cornfields. Since only 2 to 5 percent of caterpillars make it to the adult stage because of natural predators, differences in survival rates might be hard to detect. So, some ecologists feel a larger study is needed before valid conclusions can be reached.

Who would pay for the cost of a larger study, which could be between $2 and $3 million? The public source of the money is the Department of Agriculture's Biotechnology Risk Assessment Research grants program, which typically finances $1 million in research per year. A spokesperson for a trade association representing biotechnology companies stated that the private sector should not be asked to foot the bill for this kind of research.

The ability of environmental scientists to predict potential risks from biotechnology products like Bt corn will continue to grow, but the value placed by policy makers on the study of risks and benefits will have to grow as well. Corn and monarch butterflies were already among the most studied organisms on earth; less studied organisms with more complicated ecological interactions pose even greater challenges to environmental scientists and policy makers.

Nash, J. Madeleine. 2000. "Grains of Hope," Time, July 31, pp.39-46.
Yoon, Carol. 2000. "What's Next for Biotech Crops? Questions," The New York Times, December 19, pp. D1, D5.