As if industrial agriculture wasn’t polluting water enough with fertilizers and manufactured chemical pesticides, now researchers have discovered that U.S. streams are also contaminated with insecticides genetically engineered into crops.
In 2009, 63 percent of the corn planted in the U.S. was genetically modified to include the Bt toxin, a bacterial protein that kills agricultural pests like the European corn borer. According to a study published last week in Proceedings of the National Academy of Sciences, the Bt toxin is finding its way into streams.
Based on a survey of 217 streams in Indiana, the study showed that 23 percent of the streams had the Bt toxin floating in the water. The streams were sampled six months after the corn harvest.
Leaves, stems, cobs, and other detritus from genetically modified corn routinely wash into the waterways of the Midwest. The researchers demonstrated that 86 percent of surveyed streams contained such crop waste.
All of the streams that were contaminated with the Bt toxin were located 500 meters or less from a corn field. Since the landscape of the Midwest is dominated by corn production, the sample streams from the study are representative of Midwest waterways. The researchers estimated that 91 percent of streams in Iowa, Illinois, and Indiana are within that distance from a corn field.
The researchers suspect that their finding might be an unintended consequence of “no-till” farming, a practice in which the unused portions of crop are left on the fields. Even though this tactic minimizes erosion, crop detritus still ends up in adjacent streams.
Since this study was a survey, not an actual experiment, the researchers were unable to say anything about the ecological impact of the Bt toxin on aquatic ecosystems.
Additional research will be necessary to determine how GMO by-products influence the health of these Midwest streams as well as the water bodies into which they drain: the Mississippi River and the Great Lakes.