To control weeds, American farmers apply vast amounts of herbicides to their fields each year. Glyphosphate is one of the most widely used herbicides; it’s effective at killing grasses, broadleaf, and woody plants. Crops tolerate it because they are genetically modified to be glyphosphate-resistant.
You may not like the idea of eating modified foods, but this combination of herbicides and transgenic crops has made U.S. cropland the most productive in the world. And, high yields on existing croplands save other lands for nature.
But natural selection is a powerful force. As in many cases of pesticide and herbicide use, resistant individuals appear after a few years. Such is the case with glyphosphate herbicides in much of the Midwest today. In separate studies in Missouri and Iowa, researchers reported more than 60% of the farm fields harbored resistant weeds.
In fact, some of these weeds are resistant to multiple pesticides, which makes it even more difficult for farmers to maintain their fields. The need to apply a cocktail of herbicides affects the farmer’s bottom line. And it worries environmental chemists, who realize that these chemicals can have adverse effects downstream and downwind of the point of application, both on humans and wildlife.
It is difficult to see how we will feed the 7 billion people on the planet today—let alone the 10 billion who will be here in 2050—without large-scale, industrial agriculture. But, already, cracks are appearing in a formula that has worked well for the past few decades.
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Web Links
“What happens when weed killers stop killing?” Science, September 20, 2013, p. 1329
http://www.sciencemag.org/content/341/6152/1329.summary
Photo, taken on October 26, 2010, courtesy of Oscar Paradela via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.