Genetically engineered corn may harm stream ecosystems

October 10, 2007

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."
-end-


National Science Foundation

Related Corn Articles from Brightsurf:

Making sense of a universe of corn genetics
A new study details the latest efforts to predict traits in corn based on genomics and data analytics.

Redefining drought in the US corn belt
As the climate trends warmer and drier, global food security increasingly hinges on crops' ability to withstand drought.

Speedy recovery: New corn performs better in cold
Around the world, each person eats an average of 70 pounds of corn each year, with even more grown for animal feed and biofuel.

US corn yields get boost from a global warming 'hole'
The global average temperature has increased 1.4 degrees Fahrenheit over the last 100 years.

Genetic discovery may improve corn quality, yields
Researchers may be able to improve corn yields and nutritional value after discovering genetic regulators that synthesize starch and protein in the widely eaten grain, according to a Rutgers-led study.

Pollen genes mutate naturally in only some strains of corn
Pollen genes mutate naturally in only some strains of corn, according to Rutgers-led research that helps explain the genetic instability in certain strains and may lead to better breeding of corn and other crops.

Fungal mating: Next weapon against corn aflatoxin?
Native fungi combinations show promise against aflatoxin.

Scientists discover new 'architecture' in corn
New research on the US's most economically important agricultural plant -- corn -- has revealed a different internal structure of the plant than previously thought, which can help optimize how corn is converted into ethanol.

Breeding corn for water-use efficiency may have just gotten easier
With approximately 80 percent of our nation's water supply going towards agriculture, it's fair to say it takes a lot of water to grow crops.

Changing temperatures are helping corn production in US -- for now
Increased production of corn in the US has largely been credited to advances in farming technology but new research shows that changing temperatures play a significant role in crop yield.

Read More: Corn News and Corn Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.