Pollen From Genetically Altered Corn Threatens Monarch Butterfly, Study
Finds
By CAROL KAESUK YOON
ll around the country, farmers are about to finish sowing millions
of acres of a genetically altered form of corn that protects itself from
pests by producing a toxin in its tissues. But researchers report on
Thursday that this increasingly popular transgenic plant, thought to be
harmless to nonpest insects, produces a wind-borne pollen that can kill
monarch butterflies -- a species that claims the corn belt as the heart of
its breeding range.
Researchers said that the laboratory study, conducted by a team from
Cornell University, provides the first evidence that pollen from a
transgenic plant can be harmful to nonpest species. As such, the study
is likely to become part of the growing debate about whether genetically
engineered crops may have unforeseen effects on the environment.
Transgenic crops have proven tremendously popular with American farmers
in recent years. This season the new pest-resistant corn, introduced by
seed companies just three years ago, is being planted on an estimated 10
million to 20 million acres out of an 80-million-acre corn crop
nationwide. Known as Bt corn, it carries a gene derived from a bacterium,
Bacillus thuringiensis, that produces the Bt toxin, killing corn borer
pests that try to eat the plant.
The researchers fed monarch caterpillars leaves of milkweed, their only
food, which had been dusted with Bt corn pollen, regular corn pollen or no
pollen. Half of those fed Bt corn pollen died within four days, while all
those fed regular corn pollen or no pollen survived. The study, published
on Thursday in the journal Nature, was written by Dr. John E. Losey, an
entomologist, Dr. Linda S. Rayor, a behavioral ecologist, and Maureen E.
Carter, a biologist.
The Bt toxin itself is already known to be lethal to many butterflies and
moths. Researchers said this suggests that butterfly or moth species other
than the monarch could be affected by the transgenic plant, particularly
those that live on plants like milkweeds that are often found in and
around corn fields and could be dusted by Bt corn pollen. But researchers
note that the effect of Bt corn pollen on populations of wild insects is
unknown.
Academic researchers praised the study as a first step toward
understanding a previously unsuspected risk.
"Nobody had considered this before," said Dr. Fred Gould, insect
ecologist at North Carolina State University. "Should we be concerned?
Yes."
Dr. John Obrycki, an entomologist at Iowa State University, called the
new study "solid" and said: "You now have a novel means of distributing
Bt toxins in the environment. This is a technology that's being promoted
and we haven't really considered all the consequences."
Representatives from Novartis Agribusiness Biotechnology, Monsanto and
Pioneer Hi-Bred International Inc., the top sellers of Bt corn, challenged
the significance of the findings for monarch caterpillars, also known as
larvae, outside the laboratory. Researchers estimate that Bt corn is a
product worth hundreds of millions of dollars annually.
Taking issue with the methods and conclusions of the study, Rich
Lotstein, vice president of public affairs for Novartis Agribusiness
Biotechnology, said, "Even if Dr. Losey's results are real, which they
could be, the exposure is still minimal, and the impact is extremely
small, if any."
Researchers, including the authors, said it is still unknown how much of
an impact Bt corn pollen is having on wild monarch populations.
"I would be very surprised if there are no monarch larvae being killed,"
Losey said. But he added, how many are being killed, "that's the big
question."
Researchers said they do know from a study published last year that it is
the corn belt, which includes such states as Iowa, Illinois, Indiana and
Ohio, that produces about half of the monarchs that migrate each year to
Mexico.
And across that geographic expanse, said Dr. Karen Oberhauser, an
ecologist at the University of Minnesota, there was certainly potential
for corn pollen and monarch caterpillars to cross paths. "There are a lot
of monarch larvae around in July and August and that's when pollen is
being shed," she said. "The timing is exactly wrong."
How much milkweed is close enough to corn fields to be at risk of
receiving a dusting of pollen is unknown. But as Dr. Marlin Rice,
entomologist at Iowa State University, put it, in many heavily farmed
states, "if you're a monarch, odds are you're going to be close to a
cornfield."
Monarchs are not considered endangered, but Dr. Lincoln Brower, a
monarch biologist at Sweet Briar College in Sweet Briar, Va., said the
butterfly faces a growing number of pressures. The No. 1 threat, he said,
is still logging in the butterfly's winter resting grounds in Mexico.
Other threats include roadside mowing and the use of herbicides on
milkweeds.
Whatever level of threat Bt corn pollen turns out to pose, it is almost
certainly less damaging to monarchs and insect diversity in general than
the spraying of insecticides. But Obrycki said that in many areas of the
country, farmers do not typically spray for corn borer.
Still others viewed the new study as a broader sign of the danger of
transgenic crops and the need for tighter regulation.
Dr. Margaret Mellon, director of the agriculture and biotechnology
program at the Union of Concerned Scientists, said: "Why is it that this
study was not done before the approval of Bt corn? This is 20 million
acres of Bt corn too late. This should serve as a warning that there are
more unpleasant surprises ahead."
Dr. Phillip O. Hutton, chief of the microbial pesticides branch at the
Environmental Protection Agency, which regulates the commercial
availability of Bt corn, declined to comment on the new study, saying the
paper had not yet gone through the agency's scientific review. In addition
to Bt corn, the EPA has approved Bt potatoes and Bt cotton, both of which
are commercially available.
For the farmers, losses of monarch butterflies -- which neither help nor
hurt crops -- may be hard to measure against the gains from this powerful
new product. Previously, farmers had to scout their crops diligently for
signs of the corn borer and spray at just the right time in an
infestation to kill them. Now they can plant Bt corn and let the
internally produced toxins do all the work.
"It's an amazing technology," said David Linn, a corn and soybean farmer
in Correctionville, Iowa, who plants Bt and regular corn. "Does it kill
more monarchs or not? That's so far down on the list of things we have to
decide about."
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