[Editor’s note: Dr. Andrew Kniss is a weed scientist at the University of Wyoming. He co-authors the Weed Control Freaks blog. This excerpt is from his study of a 15 year dataset on herbicide use in the United States, published in the PeerJ Preprints, a non-peer reviewed venue for early communication and feedback before peer review and publication.]
Herbicide use is among the most criticized aspects of modern farming operations, especially in response to widespread adoption of genetically-engineered (GE) herbicide-resistant crops. Many previous analyses of herbicide use have relied on flawed metrics in an attempt to evaluate trends in herbicide intensity and toxicity. Here, it is shown that herbicide use intensity has increased over the last 25 years in corn, cotton, rice, and wheat.
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Herbicide area-treatments increased at a faster rate in rice and wheat compared to the glyphosate-resistant crops, so the claim that glyphosate-resistant crops are the primary driver of increasing herbicide use is at odds with the emprical data. The broader problem of herbicide-resistant weeds (rather than the artificially narrow focus on glyphosate) may certainly have played a role in increasing herbicide use for all of the crops in this analysis. The most likely explanation, though, is probably a combination of inter-related factors and is far more complex than any single scapegoat.
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Glyphosate has a lower chronic toxicity than 90% of all herbicides in this analysis, but it falls much further from the median chronic toxicity value compared to acute toxicity. Therefore, displacement of glyphosate by other herbicides is more likely to have a negative impact on chronic toxicity.
The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion and analysis. Read full, original post: Relative toxicity of herbicide use in the United States 1990 to 2015