Long-term trends in the intensity and relative toxicity of herbicide use

“Weeds are a fact of life for farmers around the world,” writes Kniss in this analysis of herbicide-use trends. He stresses the limitation of reports that measure only the weight of herbicides used, as there is tremendous variation in the toxicity of different herbicides. He shows that although herbicide use intensity has risen,  for many crops both chronic (accumulating) and acute (leading to death) herbicide toxicity has decreased. He discusses the contribution of the widely-used but lower-toxicity glyphosate to this trend, as well as the impact of glyphosate-resistant GM crops on herbicide use. Nature Comms. 10.1038/ncomms14865