Experience with herbicide resistant plants and outlook

Study by Klümper and Quaim

Klümper and Quaim showed in a broad Meta-Analysis that in GM cultures the use of chemical pesticides can be reduced by 37%. This decrease of insecticides use is caused by insecticides resistant (IR) plants. The amount of herbicides in herbicides tolerant (HT) plants could not be reduced, there is even a statistically not relevant increase. This difference is evident because IR plants prevent damages from insects and make the use of chemicals against them unnecessary, HT plants on the other hand just have the benefit that several herbicides can be replaced by one different. A very interesting point in this paper is the fact that they showed that the results from independent studies does not much differ from studies paid by the industry.[1]

Study by Benbrook

In the study of Benbrook there are converse results. He found a total increase of pesticide use in GM cultures. He also quantifies an overall decrease of insecticide use and an increase of herbicide use, but in this study there is a plus in herbicide use in total.[2]

This difference between these two articles could be explained by the designs of the two papers. Klümper and Quaim compared studies from all around the world published since 1999 (see Table S1 of their paper). Benbrook in comparison used data from the United States and compared the different years. He found a constant increase in pesticides use because of resistant weeds and insects. Maybe this effect is not included properly in the Klümper and Quaim studies because they have older material and in other countries than the U.S. GM plants are not used for such a long time and resistances had no time to develop.

Debate around the Benbrook study

The study of Benbrook is criticised by several scientists and organisations. In an online article on geneticliteracyproject.org Graham Brookes of PG Economics said, Benbrook made some subjective estimations about his data.[3] In the same article it is written that Brookes has made his own study with the same data with contradicting results. But this study is made with data from all around the world and so there is the same problem with resistant weeds and insects mentioned in the last paragraph.[4] This is not good researched or intended false information by this site. Another point that makes me sceptical about this issue is the massive critic on PG Economics because of their close bounds to the industry. (See my comment in Bettinas first blog)

Conclusion

Working on this blog showed me again what a controversy theme GM plants and that there is lot of biased and false information on the web and even in scientific papers. Not only from the industry with their financial interests but also from the Anti-GM movement. I think this is a sign that science got a massive problem with independency especially in a field like biotechnologies where a lot of money is needed to conduct studies. For future work on this topic I will use sources very thoughtful and always check the authors’ background.

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[1] Klümper, W., Qaim, M. (2014). A Meta-Analysis of the Impacts of Genetically Modified Crops. PLoS ONE 9(11)

[2] Benbrook, C.M. (2012). Impacts of genetically engineered crops on pesticide use in the U.S. - the first sixteen years. Environmental Sciences Europe 24.

[3]Entine, J.: Scientists challenge organic backer Benbrook claims that GM crops increase pesticide spraying. Found the 13. April 2015 on: http://www.geneticliteracyproject.org/2012/10/scientists-journalists-challenge-organic-scientist-benbrook-claims-that-gm-crops-increase-pesticide-spraying-harm-the-environment/

[4]Brookes G., Barfoot, P. (2012). GM Crops & Food. Biotechnology in Agriculture and the Food Chain

3(2).