In August 1999, television viewers across the country tuned in to CBS Evening News heard correspondent Wyatt Andrews say, “This growing concern over biotechnology in the food chain is also reflected in a new study, the first field study to show that America’s favorite insects, the Monarch Butterfly, can die from the pollen of gene-altered corn.”
Andrews’ statement was gross hyperbole, if not an outright misrepresentation of the research he reported.
In an effort to be the first to report important, “breaking” news, media outlets typically extract such stories from press releases issued before a scientific study is released. Press releases, aimed at getting media coverage, highlight a few “red meat” issues and attempt to simplify the findings of complex research. The studies themselves are steeped in technical terms and weighted down with statistical data—hardly attractive fare for the general public or the media that serve it.
Out of such pandering to the public interest, unnecessarily frightening stories are born.
The truth about Bt corn
A careful review of the Iowa State study Andrews was reporting, “Field Deposition of Bt Transgenic Corn Pollen: Lethal Effects on the Monarch Butterfly,” by Hansen and Obrycki, suggests the analysts reached conclusions far different from what was represented in the press release and subsequent media reports.
First, suggesting as Andrews did that the work was a “field study” is highly misleading. In fact, the only field-related activity Hansen and Obrycki undertook was to place potted common milkweed plants inside and outside plots of Bt and non-Bt corn. The researchers then counted the grains of corn pollen deposited on the milkweed leaves. The average of all samples at three meters (10 feet) was close to 10 grains of pollen/cm2 of leaf surface. At a distance of 10 meters (33 feet), the leaf samples average one grain of pollen/cm2 of leaf surface.
The second part of the experiment was a “laboratory simulation” of caterpillars grazing in the field. The caterpillars grazed on the milkweed samples for 48 hours. From this part of the experiment, the researchers found:
- 20 percent higher mortality, plus or minus 3 percent, for caterpillars grazing on the straight-up Bt corn pollen. In other words, seven caterpillars died, give or take one. The “significance of this research,” Hansen and Obrycki write, “is that seven caterpillars died.”
- When caterpillars grazed on 73 milkweed samples washed of their Bt pollen, the researchers reported a 3 percent increase in caterpillar mortality. Two caterpillars out of 73 died. Given that the experiment’s non-Bt control sample had only 36 caterpillars in it, if just one caterpillar had died of natural causes in that control, it would have had the same 3 percent sample mortality as “washed samples.”
- Hansen and Obrycki also find that “mortality was not correlated with the number of pollen grains on the leaf or the plant location.” While there were not enough samples to describe those relationships, it appears that the relationship was measured, but showed no correlation.
Force-feeding can be lethal
The third part of the Hansen and Obrycki experiment consisted of force-feeding 234 caterpillars greenhouse plants coated with field-collected pollen, on 18 different treatments. The caterpillars were given no food without pollen, so they had no choice but to eat it. The 1,300 grains/cm2 leaf concentration is nearly 100 times the concentration of pollen measured three meters (10 feet) from the field.
Not surprisingly, that level of pollen proved lethal to 70 percent of the young caterpillars and almost 60 percent of the older caterpillars.
The lesson learned from all of this? When you force-feed caterpillars high concentrations of Bt pollen, they die.
True field studies show less risk
In November 1999, a panel of researchers met in Chicago to present the results of actual field studies of Monarch Butterflies. From preliminary data, they concluded Monarchs are not in fact at risk from Bt corn because:
- Bt corn pollen concentrations fall off very rapidly a short distance from the cornfield.
- Pollen concentrations on milkweed leaves near cornfields generally aren’t high enough to harm Monarch larva and other non-target moths and butterflies.
- Monarchs apparently do not like Bt corn pollen and avoid it when possible.
- Cornfields contain very few milkweed plants. (“That’s why farmers cultivate and use herbicides, to kill weeds.”)
- Climatic conditions and other factors greatly reduce exposure to pollen in the wild.
The reliability of the Iowa State study was discussed by Anthony Shelton, associate director of research at Cornell University, where another flawed Monarch Butterfly study received widespread coverage about a year earlier. Shelton had been very critical of the Cornell study, even though it was conducted at his own university.
Shelton said the Iowa State researchers came to “conclusions that exceeded their data, and some of their statements are simply off the mark.” Moreover, “they did not provide any evidence that (a toxic) dose would be encountered by Monarchs in the field because of the lack . . . of biological data on milkweed distribution and the occurrence of Monarchs.” More detailed and extensive field studies are being done by a group of independent scientists from the United States and Canada. “So far, they have failed to see the effects predicted (by the Iowa State authors),” Shelton noted.
Truth fares poorly in the press
The Environmental Protection Agency has been monitoring Bt corn research since the corn was first approved for sale in the United States. Noted Stephen Johnson, EPA Deputy Assistant, “Based on what we’ve seen so far, we’re not seeing any impact on any of the non-target organisms, particularly the Monarch Butterfly.”
The media’s crusade against Bt corn was launched by a single study, poorly designed, poorly implemented, and reporting results that were not statistically significant. Score a big victory for misleading media hype, and a disappointing loss for truth and reality.
Terry Francl and Mark Jenner are policy analysts with the American Farm Bureau Federation.