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Union of Concerned Scientists
August 1999 |
Monarch Update
Posted August 6, 1999
Bt Corn/Monarch Study Halts Approvals in Europe and Japan
Both the European Commission and the Japanese government suspended approvals of Bt corn in the wake of a Cornell University report that the crop may threaten monarch butterflies. Though Europe has only a small population of monarchs (in Spain) and Japan has none, the government actions reflected worries that native moths and butterflies may be at risk.
The report prompted the European Commission to halt the review process for both Pioneer Hi-Bred and DeKalb/Monsanto Bt-corn varieties. Approvals given earlier to Novartis and Monsanto varieties were unaffected by the suspension.
At the same time, the Japanese Ministry of Agriculture, Forestry and Fisheries (MAFF) froze reviews of Bt crops pending development of new criteria for assessing ecological risks. This freeze is the first Japanese regulatory decision on engineered crops based on environmental concerns. Previously, the government had focused on risks to humans. A MAFF committee is expected to release protocols for evaluating ecological risks by the end of the year.
The report also provoked a response in Mexico where huge masses of monarch butterflies overwinter. Greenpeace and other activists called on the government to ban Bt corn.
Sources: A. Saegusa, "Japan tightens rules on GM crops to protect the environment," Nature 399:719, June 24, 1999; S. Malcolm, Western Michigan University, personal communication, May 1999; "Bt maize and monarch butterflies," AgBiotech Reporter 16 (6):1-2, June 1999.
Herbicide-Resistant Crops--Another GE Threat to Monarchs?
Like engineered Bt corn, herbicide-resistant crops may take a toll on monarch butterfly populations, but for different reasons, according to Dr. O.R. Taylor, a University of Kansas entomologist. Taylor, who also coordinates a monarch conservation network called Monarch Watch, was interviewed in the April Environmental Review. He explained that the rapid adoption of engineered herbicide-resistant corn and soybeans may seriously decrease the milkweed population in fields, which, in turn, may lead to a decline in monarchs, as milkweed is the sole food source for the butterfly caterpillars.
Traditional weed-control regimes are not as great a threat because large numbers of milkweeds typically survive the herbicides applied to corn and soybeans. This is one of the problems that Monsanto and other companies set out to solve by engineering crops to resist herbicides, like glyphosate (Roundup). With the new crops, farmers can use broad-spectrum weed killers to rid fields of milkweed and other recalcitrant weeds which sprout after the crop has started to grow. Without engineered resistance, glyphosate can only be used to kill weeds before planting. As more and more herbicide-resistant crops replace traditional ones--nearly half the soybean crop is expected to be herbicide-resistant this year--milkweed stands could well decline, followed by a decrease in the monarch population.
This possibility takes on a more ominous dimension in light of new information on monarch breeding. The Midwest is an important breeding ground for the adult monarchs that migrate south every year to spend the winter roosting in forests in Mexico where they await a signal to begin their annual northern migration. Canadian scientists have recently found that a substantial portion, roughly 50 percent, of the monarchs that overwinter in Mexico originate from a relatively small area between Nebraska and Ohio--the heart of US corn and soybean production--and the site of rapid adoption of herbicide-resistant crops.
Sources: B. Hartzler, "Monarch butterflies and herbicide resistant crops," Iowa State University, www.weeds.iastate.edu/weednews/monarchs.htm; "Monarch butterflies may be threatened in their North American range," Environmental Review 6(4):1-9, April 1999; "Monarchs and their roots," Science 283:171, January 8, 1999; L. Wassenaar and K. Hobson, "Natal origins of migratory monarch butterflies at wintering colonies in Mexico: new isotopic evidence," Proceedings National Academy of Sciences 95:15436-39, December 1998; Monarch Watch at www.monarchwatch.org.
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