"The only thing wrong with scientists is that they don't understand science. They don't know where their own institutions came from, what forces shaped them, and they are wedded to an anti-historical way of thinking which threatens to deter them from ever finding out."
Eric Larrabee

Effects of Bt pollen in aquatic ecosystems

02 Nov 2007

Below is the relevant NSF press release:

Toxins in transgenic crop byproducts may affect headwater stream ecosystems E. J. Rosi-Marshall, J. L. Tank, T. V. Royer, M. R. Whiles, M. Evans-White, C. Chambers, N. A. Griffiths, J. Pokelsek, and M. L. Stephen PNAS 2007 104: 16204-16208

Ecological impacts of genetically engineered corn are particularly important because
of increased corn demand created by biofuels production

A new study indicates that a popular type of genetically engineered corn--called Bt
corn--may damage the ecology of streams draining Bt corn fields in ways that have
not been previously considered by regulators. The study, which was funded by the
National Science Foundation, appears in the Oct. 8 edition of The Proceedings of the
National Academy of Sciences.

This study provides the first evidence that toxins from Bt corn may travel long
distances in streams and may harm stream insects that serve as food for fish. These
results compound concerns about the ecological impacts of Bt corn raised by previous
studies showing that corn-grown toxins harm beneficial insects living in the soil.

Licensed for use in 1996, Bt corn is engineered to produce a toxin that protects
against pests, particularly the European corn borer. Bt corn now accounts for
approximately 35 percent of corn acreage in the U.S., and its use is increasing.

"As part of the licensing process for genetically modified crops, the U.S.
Environmental Protection Agency (EPA) was responsible for testing and identifying
potential environmental consequences from the planting of Bt corn," says Jennifer
Tank, who is from the University of Notre Dame and is a member of the team studying Bt corn.

"To fulfill this requirement, EPA completed studies that assumed that plant parts
would remain in fields without being carried away by streams draining agricultural
lands" says Tank. In addition, EPA only tested the impacts of Bt corn on small lake
organisms that are typically used to test the impacts of chemicals on aquatic
ecosystems.

The agency did not evaluate the impacts of Bt corn on organisms that live in
streams--even though Midwest agricultural lands where Bt corn is grown are heavily
intersected by streams draining the landscape. But despite the limitations of its
tests, EPA concluded that Bt corn "is not likely to have any measurable effects on
aquatic invertebrates."

To more comprehensively evaluate the ecological impacts of Bt corn than did the EPA, the research team did the following:

- Measured the entry of Bt plant parts--including pollen, leaves and cobs--in 12
streams in a heavily farmed Indiana region. The research team's results demonstrate that these plant parts are washing into local steams. Moreover, during storms, these plant parts are carried long distances and therefore could have ecological impacts on downstream water bodies, such as lakes and large rivers.

- Collected field data indicating that Bt corn pollen is being eaten by caddisflies,
which are close genetic relatives of the targeted Bt pests. Todd V. Royer, a member
of the research team from Indiana University, says that caddisflies "provide a food
resource for higher organisms like fish and amphibians."

- Conducted laboratory tests showing that consumption of Bt corn byproducts
increased the mortality and reduced the growth of caddisflies. Together with field
data indicating that the caddisflies are eating Bt corn pollen, these results
"suggest that the toxin in Bt corn pollen and detritus can affect species of insects
other than the targeted pest," Tank said.

Royer says that "if our goal is to have healthy, functioning ecosystems, we need to
protect all the parts. Water resources are something we depend on greatly."

"Overall, our study points to the potential for unintended and unexpected
consequences from the widespread planting of genetically engineered crops," Tank
said. "The exact extent to which aquatic ecosystems are, or will be, impacted is
still unknown and likely will depend on a variety of factors, such as current
ecological conditions, agricultural practices and climate/weather patterns."

James Raich, a National Science Foundation program director, adds that "increased
use of corn for ethanol is leading to increased demand for corn and increased
acreage in corn production. Previous concerns about the nutrient enrichment of
streams that accompany mechanized row-crop agriculture are now compounded by toxic corn byproducts that enter our streams and fisheries, and do additional harm."

The Bt corn researchers stress that their study should not be viewed as an
indictment of farmers. "We do not imply that farmers are somehow to blame for
planting Bt corn, nor are they responsible for any unintended ecological
consequences from Bt corn byproducts," Tank said. "Farmers are, to a large extent,
required to use the latest technological advances in order to stay competitive and
profitable in the current agro-industrial system."