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A fourteen year study demonstrates an increase of herbicide usage among farmers with genetically modified crops due to growing weed resistance

The study followed 5000 soybean and 5000 maize farmers in the U.S. from 1998 to 2011 and found that farmers who grew genetically modified soybean plants containing a gene resistant to glyphosate (a chemical found in many herbicides) used 28% more herbicides than those who grew unmodified soybeans.


Economist Federico Ciliberto leading GMO research.
The study was conducted by four economists: Federico Ciliberto of the University of Virginia, Edward D. Perry of Kansas University, David A. Hennessey of Michigan State University, and GianCarlo Moschini of Iowa State University.

The four economists examined annual data from over ten thousand farmers in the U.S. to discover trends among farmers using genetically modified crops and create the largest study ever performed on widespread use of genetically modified crops and pesticide usage.

Lead researcher Ciliberto states, "The fact that we have 14 years of farm-level data from farmers all over the U.S. makes this study very special. We have repeated observations of the same farmers and can see when they adopted genetically modified seeds and how that changed their use of chemicals."

The increased dependence on genetically engineered soybean and maize crops show a decrease in insecticides but an increase in herbicides.

The genetically modified soybean crops in the study contained a glyphosate-resistant gene while the genetically modified maize contained both a glyphosate-resistant gene and an insect-resistant gene. This is indicative of the state of GMOs: since 2008, 80% of soybean and maize crops in the U.S. are genetically engineered with a glyphosate-resistant gene.

Because maize crops were modified to have a detrimental effect against insects, it was unsurprising to discover that among the farmers studied, there was a trend of lesser insecticide use. However, what causes the most concern is the fact that farmers who used genetically modified crops used 28% more herbicides.

A: Adoption of three types of genetically modified crops in the U.S.
B: Insecticide use in maize
C: Herbicide use in soybeans
D: Herbicide use in maize

The reasoning is that while the crops are engineered to be resistant to glyphosate, many weeds have also evolved to be resistant. Ciliberto explains, In the beginning, there was a reduction in herbicide use, but over time the use of chemicals increased because farmers were having to add new chemicals as weeds developed a resistance to glyphosate."

The future of GMOs will only become more controversial due to increases in herbicide usage, the general public's concern for safety, and advancements in technology

Another portion of the study was devoted to the environmental impacts of increased herbicide usage. Ciliberto and his colleagues used a measure called the environmental impact quotient (EIQ) and found that the adoption of genetically modified soybeans was related to a negative impact on the environment.

As farmers have to rely on more herbicides to kill glyphosate-resistant crops, local bodies of water are forced to uptake more chemicals, which in turn damages local ecosystems. Ciliberto stated that he "did not expect to see such a strong pattern."

A second unrelated study explains that this trend, along with a combined fear of the safety of GMOs may lead to an eventual decrease in genetic modifications of foods. The study states in its conclusion that, "The greatest concern expressed by the consumers of agricultural products addresses the safety of foods from transgenic crops. Science has not been able to successfully answer this concern, and the agricultural industry has not been effectively responsive to consumer fears."

video
A local consumer expressing her uncertain stance on GMOs.

Furthermore, as technology continues to expand at an incredible rate, the control scientists will have with handling genetic material will only increase. The future of GMOs remains uncertain.

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