The impacts of genetically modified crops on pesticide use and toxicity

As of 2020, genetically modified (GM) crops dominate the production of corn, cotton and soybean in the United States. This new crop technology has been widely adopted, largely driven by farmers' expectations of lower pesticide costs and savings in management time. Despite the private benefits associated with GM crops, this technology may indirectly impact the environment through externalities such as incentivizing the use of new or different levels of agrochemicals. In this paper, I study this relationship by estimating the causal impact of GM crop adoption on pesticide use and toxicity relative to non-GM crops in the United States. To overcome data limitations, I use a novel approach to estimate GM crop adoption at the county level which also addresses the concern that GM crop adoption may be correlated with farm characteristics that could affect outcomes directly. More specifically The study indicates that the adoption of GM crops has diverse effects on pesticide use and toxicity. Specifically, GM corn adoption leads to a significant decrease in herbicide use and toxicity, while GM cotton adoption results in an increase, primarily due to glyphosate. No change was observed with GM soy, largely due to a shift from non-glyphosate to glyphosate herbicides. Insecticide use and toxicity showed statistically insignificant decreases for GM corn and cotton. Furthermore, further analyses suggest that over time, the effects of GM crop adoption on pesticide use and toxicity tend to diminish across all crops and traits. These findings suggest a need for continuous monitoring and management strategies to sustain the benefits of GM crops while mitigating potential negative impacts on the environment and human health. It also highlights the importance of considering the dynamic nature of these effects over time.