GM corn polluting Midwest streams

Stream ecosystems are tightly linked to agricultural fields and should be considered when adopting new agricultural technologies

A new published study reveals that insecticidal proteins from genetically modified corn crops are entering streams throughout the Midwestern United States. The proteins enter streams through runoff and when corn leaves, stalks, and plant parts are washed into stream channels, and are being found even six months after harvest. The study’s authors say more research is needed to determine the impacts of the GM material on the streams’ ecosystems. The study was published in September in the Proceedings of the National Academy of Sciences (PNAS).

Genetically modified corn varieties accounted for more than 86% of the corn seed planted in 2010. Corn engineered to release an insecticide that wards off the European corn borer, commonly referred to as Bt corn, comprised 63% of crops. The tissue of these plants has been modified to express insecticidal proteins, one of which is commonly known as Cry1Ab.

GMOs persist 6 months after harvest

Following an assessment of 217 stream sites in Indiana, the paper’s authors found dissolved Cry1Ab proteins from Bt corn present in stream water at nearly a quarter of the sites, including headwater streams. Eighty-six percent of the sampled sites contained corn leaves, husks, stalks, or cobs in their channels; at 13% of these sites corn byproducts contained detectable Cry1Ab proteins. The study was conducted six months after crop harvest, indicating that the insecticidal proteins in crop byproducts can persist in the landscape.

Using US Department of Agriculture land cover data, and GIS modeling, the authors found that all of the stream sites with detectable Cry1Ab insecticidal proteins were located within 500 meters of a corn field.  Furthermore, given current agricultural land use patterns, 91% percent of the streams and rivers throughout Iowa, Illinois, and Indiana —some 159,000 miles of waterways—are also located within 500 meters of corn fields.

“Our study demonstrates the persistence and dispersal of crop byproducts and associated transgenic material in streams throughout a corn belt landscape even long after crop harvest,” said University of Notre Dame ecologist Jennifer Tank, and one of the authors of the study. “This suggests that corn crop byproducts and any associated insecticidal proteins may enter streams across the corn belt states.”

Dr. Emma J. Rosi-Marshall, a aquatic ecologist at the Institute of Ecosystem Studies and another one of the study’s researchers, said, “Our research adds to the growing body of evidence that corn crop byproducts can be dispersed throughout a stream network, and that the compounds associated with genetically-modified crops, such as insecticidal proteins, can enter nearby water bodies.”

This wasn’t the first time that GM materials have been found in Midwest streams.

In a 2007 PNAS paper, Tank and a group of researchers demonstrated that GM materials from corn (pollen, leaves, cobs) do, in fact, enter streams in the agricultural Midwest and can be subsequently transported to downstream water bodies.

Research needed on impacts of GMO on ecosystems

After corn crops are harvested, a common agricultural practice is to leave discarded plant material on the fields. This “no-till” form of agriculture minimizes soil erosion, but it also sets the stage for corn byproducts to enter nearby stream channels.

Rosi-Marshall concludes, “The tight linkage between corn fields and streams warrants further research into how corn byproducts, including Cr1Ab insecticidal proteins, potentially impact non-target ecosystems, such as streams and wetlands.” These corn byproducts may alter the health of freshwaters. Ultimately, streams that originate in the Corn Belt drain into the Mississippi River and the Great Lakes.

Negative impacts from GM corn on farm streams have already been documented. In 2007, a published study by researchers at Indiana University found that GM corn produced increased mortality and reduced growth in caddisflies, aquatic insects that are a food resource for higher organisms like fish and amphibians.

(Copyright The Organic & Non-GMO Report, November 2010)