Counterintuitive Finding Shows Herbicide Use In Genetically Modified Crops Has Actually Increased
The promise by Monsanto and producers of genetically modified crops was that farmers could use less chemicals and produce a greater yield. That’s about as true as honesty in politics. A study published this week by Washington State University research professor Charles Benbrook finds that the use of herbicides in the production of three genetically modified herbicide-tolerant crops — cotton, soybeans and corn — has actually increased.
This counterintuitive finding is based on an exhaustive analysis of publicly available data from the U.S. Department of Agriculture’s National Agriculture Statistics Service. Benbrook’s analysis is the first peer-reviewed, published estimate of the impacts of genetically engineered (GE) herbicide-resistant (HT) crops on pesticide use.
It is confirming earlier US government data showing that in the US, GM crops have produced an overall increase, not decrease, in pesticide use compared to conventional crops. Not only that promises of greater yields are also unfounded.
GM crops have not increased the yield potential of any commercialised crops. In fact, studies show that the most widely grown GM crop, GM soya, has suffered reduced yields.
A report that analyzed nearly two decades worth of peer reviewed research on the yield of the primary GM food/feed crops, soybeans and corn (maize), reveals that despite 20 years of research and 13 years of commercialization, genetic engineering has failed to significantly increase US crop yields. The author, former US EPA and US FDA biotech specialist Dr Gurian-Sherman, concludes that when it comes to yield, “Traditional breeding outperforms genetic engineering hands down.”
In the USDA study, which appeared in the the open-access, peer-reviewed journal “Environmental Sciences Europe,” Benbrook writes that the emergence and spread of glyphosate-resistant weeds is strongly correlated with the upward trajectory in herbicide use. Marketed as Roundup and other trade names, glyphosate is a broad-spectrum systemic herbicide used to kill weeds. Approximately 95 percent of soybean and cotton acres, and over 85 percent of corn, are planted to varieties genetically modified to be herbicide resistant.
Atrazine is the second-most widely used herbicide in the U.S. More than 75 million pounds of it are applied to corn and other crops, and it is the most commonly detected pesticide contaminant of groundwater, surface water and rain in the U.S.
Men exposed to high amounts of the substance are far more likely than men with less contact to have diluted or deformed and sluggish sperm. Each of the semen problems can reduce the ability of sperm to reach and fertilize an egg and could make conception harder.
“Resistant weeds have become a major problem for many farmers reliant on GE crops, and are now driving up the volume of herbicide needed each year by about 25 percent,” Benbrook said.
Data from the US Department of Agriculture indicate that the use of glyphosate on major crops went up by more than 15 fold between 1994 and 2005. The EPA estimated in 2000-2001 that 100 million pounds of glyphosate are used on lawns and farms every year, and over the last 13 years, it has been applied to more than a billion acres.
It did not take long for glyphosate-resistant weeds to appear, just as weeds resistant to every herbicide used in the past had appeared. The Weed Science Society of America reported nine weed species in the United States with confirmed resistance to glyphosate; among them are strains of common ragweed (Ambrosia artemisiifolia), common waterhemp (Amaranthus rudis), giant ragweed (Ambrosia trifida), hairy fleabane (Conyza bonariensis), horseweed (Conyza canadensis), Italian ryegrass (Lolium multiflorum), johnsongrass (Sorghum halepense), rigid ryegrass (Lolium rigidum), and palmer pigweed (Amaranthus palmeri).
The annual increase in the herbicides required to deal with tougher-to-control weeds on cropland planted to GE cultivars has grown from 1.5 million pounds in 1999 to about 90 million pounds in 2011.
Herbicide-tolerant crops worked extremely well in the first few years of use, Benbrook’s analysis shows, but over-reliance may have led to shifts in weed communities and the spread of resistant weeds that force farmers to increase herbicide application rates (especially glyphosate), spray more often, and add new herbicides that work through an alternate mode of action into their spray programs.
About the Author
Natasha Longo has a master’s degree in nutrition and is a certified fitness and nutritional counselor. She has consulted on public health policy and procurement in Canada, Australia, Spain, Ireland, England and Germany.
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