It's been a big week for CBS television. Not only did the network air the grand finale of the popular Survivor, but CBS News broke news about the Monarch butterfly edition of Survivor.
The subject: How many butterflies will survive when plucked from their natural environment and forced to live on a toxic island?
"It is the first field study to show that America's favorite insect, the monarch butterfly, can die from the pollen of gene-altered corn," reported CBS News' Wyatt Andrews about a new study out of Iowa State University.
But Andrews overreacted. The new study is as much a "field study" — and as realistic — as Survivor. The alarm over biotech corn and Monarch butterflies started last year when Cornell University researchers reported pollen from so-called "Bt corn" killed Monarch larvae under laboratory conditions. Conditions that including forcing the Monarchs to eat toxic pollen — or not eat at all.
Bt corn has been genetically modified to carry a protein toxic to the European corn borer, a devastating pest. The protein is toxic to other moths and butterflies, but they don't eat corn pollen. Before Bt corn was approved, the Environmental Protection Agency concluded Monarch larvae would have little exposure to the pollen.
Amidst last year's media hysteria — "Engineered Corn Kills Butterflies, Study Says," was USA Today's headline — scientists said no evidence showed Monarchs in the wild would ever consume harmful amounts of the pollen. In the wake of that perspective and further research, the alarm subsided.
But since media sensationalism never goes out of style, the new study easily resurrected the butterfly scare.
Iowa State University researchers — led by a graduate student — again reported Bt corn pollen may be toxic to butterfly larvae. It's being called a "field study," but there was very little "field work" involved.
The researchers put potted milkweed plants, the main food of Monarch butterfly larvae, in and around Bt corn test plots. When Bt corn pollen fell on the milkweed leaves, the researchers removed the leaves to a laboratory where leaf sections about the size of a fingernail were placed in lab dishes. The researchers put a Monarch larva on each tiny section. Two days later, the researchers counted how many larvae died.
Some "field study." The larvae had no choice of food. They couldn't move to clean leaf surfaces. Rain couldn't wash the pollen away. The researchers placed the larvae on the top sides of the leaf sections when, in the wild, the larvae would most likely be hatched on the underside, away from pollen.
Even so, only 20 percent of the larvae died after two days.
Worse still, the Iowa State researchers used the type of Bt corn pollen most toxic to Monarch larvae. Called "Event 176," it is about 50 times more toxic than pollen from other Bt corn varieties. But it accounts only for about 2 percent of the Bt corn market and is being phased out by its producer, Novartis Seeds Inc. Scientists know from extensive research that Monarch larvae and other beneficial insects can withstand much higher doses of the pollen from the Bt corn that farmers usually plant.
Even so, the Iowa State researchers reported that beyond one meter from the cornfield, no sample of Bt corn pollen, including from around Event 176 fields, exceeded the dose that could harm the Monarch larvae.
Not surprisingly, the media overlooked these key facts — and it's not the first time.
Dr. Mark Sears of Canada's University of Guelph reported last February that levels of Bt corn pollen measured at the edge of cornfields had no effect on Monarch larvae. And Sears measured essentially no pollen five meters away from cornfields. His study received almost no media attention.
There was scant coverage of this summer's University of Illinois field study, which reported Bt corn pollen didn't harm black swallowtail butterfly larvae placed on host plants in and around Bt cornfields.
Little attention was paid to a recent EPA report reviewing the safety of Bt corn for non-target species. This report was so convincing that Greenpeace withdrew its lawsuit challenging the EPA's approval of Bt corn. The withdrawal, news by any standard, received no coverage.
There was some media coverage last November when 20 researchers from several universities met near Chicago to present the results of actual field studies of Monarch butterflies. None of those studies have been published yet. The researchers want to collect two summers' worth of data and will finish this summer. But at the meeting, heavily covered by the media, the researchers presented preliminary data indicating Monarchs aren't at risk from Bt corn, including:
—
The concentration of Bt corn pollen drops off very rapidly a short distance from the cornfield.
The pollen concentration found on milkweed leaves near cornfields generally isn't sufficient to harm Monarch larvae and other non-target moths and butterflies.
Monarchs apparently don't like Bt corn pollen and avoid it when possible.
Cornfields have very little milkweed.
Climatic conditions and other factors greatly reduce exposure to pollen in the wild.
New York Times'
She is technically correct by qualifying the study as "published." But did Yoon simply forget the trip she made to cover the November meeting?
Also overlooked (ignored?) was Dr. Anthony Shelton, professor of Entomology at Cornell's New York State Agricultural Experiment Station, who was very critical of the Cornell study even though it was conducted at his own university. Shelton says the Iowa State researchers make "conclusions that exceed their data and some of their statements are simply off the mark."
"They do not provide any evidence that [a toxic] dose would be encountered by Monarchs in the field because they lack ... the biological data on milkweed distribution and the occurrence of Monarchs," Shelton said. "More detailed and extensive field studies are being done by a group of independent scientists from the U.S. and Canada. So far, they have failed to see the effects predicted (by the Iowa State authors)," he added.
It seems Bt corn research only sees the light of day when researchers kill Monarch butterfly larvae through unrealistic conditions. It's not good science. But, like Survivor, it makes good television.
— Steven Milloy is a biostatistician, lawyer, adjunct scholar at the Cato Institute and publisher of Junkscience.com.
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