Increased environmental impact of toxic pesticides
10 April 2021 / Expectations that the cultivation of transgenic plants would lower the impact of pesticides on the environment have failed to materialise. This failure was confirmed in a recent study published in the magazine, Science, based on official data from the US. The experts compared volume and toxicity of pesticides applied in fields with genetically engineered (GE) plants to fields with conventional agriculture. The conclusion: in recent years there has been a strong increase in pesticides impacting the environment, with and without transgenic plants.
Most of the plants cultivated in the US produce insecticides and are resistant to herbicides such as glyphosate. The environmental impact due to pesticides has increased in both variants.
One reason is a growing number of weedy species that have adapted to glyphosate. Transgenic plants are also a crucial driver in this context since GE is used to make plants glyphosate-resistant, e.g. soybeans, maize, cotton, oilseed rape and sugar beet. The crops are subsequently intensively sprayed with the herbicide. Whereas all weeds were susceptible to glyphosate prior to the introduction of transgenic plant cultivation, meanwhile in the US, more than 15 weedy species have become glyphosate-resistant. The current study uses GE soybeans as an example to show that the volume of sprayed herbicides has strongly increased.
Similar effects have been observed in insecticidal plants. They produce a toxin (Bt) which occurs naturally in soil bacteria (Bacillus thuringiensis). Meanwhile, pest insects, such as the root worm, have adapted to the toxins to such a degree that the cultivation of Bt plants has been restricted in the US. Maize plants engineered to produce a specific insecticidal RNA have also not brought the expected breakthrough. The current study shows there was no reduction in the use of controversial insecticides, i.e. neonicotinoids used against corn borer, in fields where the insecticidal GE maize is grown.
The new publication highlights an overall trend in the US: while over the years there has been a reduction in the volume of insecticides sprayed on fields, the insecticides currently applied are much more toxic. Consequently, there has been a significant increase in the environmental impact due to pesticides, with and without GE plants.
Industry and experts close to industry claim there has been a reduction in pesticides ascribable to the cultivation of transgenic plants. However, as has also been shown in other publications, this is not the case.
Christoph Then, email@example.com, Tel + 49 (0) 151 54638040