The delicate black and orange monarch butterfly stands as a symbol of
the environmental movement.
Referred to as "the Bambi of the
insect world," the attractive butterfly is listed as a threatened
species in Canada, and has been used by lobbying groups to call
attention to the frailties of the natural environment for everything
from diminishing habitats to pesticide use.
But despite earlier findings, recent research has struck genetically modified corn from the list of potential threats to the species.
"In most cases, there was no effect whatsoever," said Mark Sears, a University of Guelph entomologist who conducted a two-year study on the butterflies.
Sears was one of several researchers from Canada and the United States who investigated what threat genetically modified corn varieties may pose to monarch butterflies. They found that the current commercial hybrids have little or no effect on the butterfly.
Very high concentrations of the pollen from the transgenic corn can be harmful to the insects in the larval stage, but are unlikely to be found in nature. "It would take a lot of pollen for any caterpillar to succumb to it," said Sears. "Each grain is not very toxic."
A 1999 study published in the scientific journal Nature raised alarm worldwide that the very existence of the popular butterfly was in jeopardy from the pollen of transgenic corn varieties currently being produced in the United States and Canada.
"It was a landmark event," said Sears of the original research, "especially in environmentalists' eyes."
Early Concerns
Experiments looked at Bt (Bacillus thuringiensis) corn that had been modified to incorporate a gene making the plant tissue toxic to a common pest, the European corn borer.
Although the corn plant is harmless to humans, researchers studied its impact on other non-target organisms that consume it—specifically, whether the modified crop could be lethal to the larvae of the monarch butterfly.
Sears estimates that nearly 20 percent of corn grown in the corn belt in the United States and Canada is of a transgenic variety.
