Truth: The herbicides used with GM crops harm biodiversity
Myth at a glance
The UK government-funded Farm Scale Evaluations (FSEs) looked at the effects on farmland wildlife of the cultivation of four GM herbicide-tolerant crops, compared with non-GM crops grown under intensive chemically-based management.
The results for sugar beet and oilseed rape showed that GM herbicide-tolerant crop management reduced weeds and weed seeds and therefore would damage farmland wildlife.
For maize the results showed GM crop management to be better for wildlife than conventional chemically intensive management. However, the conventional weed control used the toxic herbicide atrazine, which was banned in Europe before the FSE results were published.
The outcome of the FSEs was that all but one of the GM crops tested was worse for biodiversity than non-GM crops grown under intensive chemically-based management. No GM crops were subsequently commercially planted in the UK.
In the late 1990s in the UK, concerns were expressed that the use of GM herbicide-tolerant crops might have an indirect impact on farmland biodiversity by reducing weeds in arable fields and field margins. Farmland birds, such as the skylark, were already badly affected by intensive arable production.
In the early 2000s the UK government decided to fund open field trials (the Farm Scale Evaluations or FSEs) to test the effects of GM crop management compared with conventional chemically intensive non-GM crop management. It appointed a consortium of research institutions to carry out the research over four years. The following GM crops were grown:
- Roundup Ready sugar beet and fodder beet
- Glufosinate ammonium-tolerant winter oilseed rape (canola)
- Glufosinate ammonium-tolerant spring oilseed rape
- Glufosinate ammonium-tolerant fodder maize (in which the whole crop was made into silage and fed to dairy cattle).1
The researchers investigated whether the changes in weed management associated with herbicide-tolerant GM crops would reduce weed levels and have wider impacts on farmland biodiversity.1 The direct toxic effects of herbicides on wildlife were not studied.
Each field was divided in half, with one half planted with a non-GM variety managed according to the farmer’s normal practice, and the other half planted with a GM herbicide-tolerant variety.
The results for beet and oilseed rape showed that GM herbicide-tolerant crop management significantly reduced weeds and weed seeds and therefore would further damage farmland wildlife.1,2,3,4,5,6,7,8,9
For maize the results showed GM herbicide-tolerant crop management to be better for wildlife than conventional chemically intensive management.1,2,3,4,5,6,7,8,9 However, this was because the conventional weed control used the highly toxic herbicide atrazine. Before the results of the FSEs were published, atrazine was banned in Europe.10
A more useful comparator for the GM herbicide-tolerant maize would have been maize grown in an organic or integrated pest management (IPM) system, which eliminate or reduce herbicide use. In the EU, this is not a purely idealistic notion. A 2009 European Directive asks member states to implement national plans to adopt integrated pest management and alternative approaches in order to reduce pesticide use.11
After the results of the FSEs were published the UK government announced that it would not approve the GM oilseed rape or sugar beet applications for commercial growing, but would approve the glufosinate-tolerant GM maize, known as Chardon LL. However, within a few weeks, the developer company Bayer (formerly Aventis) announced that it would not be commercializing this GM maize variety in the UK. The outcome was that no GM crops were approved for UK cultivation.10
“The commercialization of GM beet and oilseed rape could be disastrous for birds. The government is committed to reversing bird declines and has promised to ban GM crops if they damage the environment. The Farm Scale Evaluations show that two GM crops harm the environment and ministers now have no choice but to refuse their approval.”
– Dr Mark Avery, director of conservation at the UK’s Royal Society for the Protection of Birds (RSPB) and member of the UK government’s Science Review Panel12
The overall outcome of the FSEs was that the management of all but one of the GM herbicide-tolerant crops tested was more damaging to farmland wildlife than the management of non-GM crops grown under a conventional chemically intensive system. GM maize was only found better for wildlife because the non-GM comparator was grown with the toxic herbicide atrazine.
- DEFRA. Managing GM crops with herbicides: Effects on farmland wildlife. Farmscale Evaluations Research Consortium and the Scientific Steering Committee; 2005. Available at: http://bit.ly/P8ocOW.
- Hawes C, Haughton AJ, Osborne JL, et al. Responses of plants and invertebrate trophic groups to contrasting herbicide regimes in the Farm Scale Evaluations of genetically modified herbicide-tolerant crops. Philos Trans R Soc Lond B Biol Sci. 2003;358:1899-913. doi:10.1098/rstb.2003.1406.
- Roy DB, Bohan DA, Haughton AJ, et al. Invertebrates and vegetation of field margins adjacent to crops subject to contrasting herbicide regimes in the Farm Scale Evaluations of genetically modified herbicide-tolerant crops. Philos Trans R Soc Lond B Biol Sci. 2003;358:1879-98. doi:10.1098/rstb.2003.1404.
- Brooks DR, Bohan DA, Champion GT, et al. Invertebrate responses to the management of genetically modified herbicide-tolerant and conventional spring crops. I. Soil-surface-active invertebrates. Philos Trans R Soc Lond B Biol Sci. 2003;358:1847-62. doi:10.1098/rstb.2003.1407.
- Heard MS, Hawes C, Champion GT, et al. Weeds in fields with contrasting conventional and genetically modified herbicide-tolerant crops. II. Effects on individual species. Philos Trans R Soc Lond B Biol Sci. 2003;358:1833-46. doi:10.1098/rstb.2003.1401.
- Firbank LG. Introduction: The farm scale evaluations of spring-sown genetically modified crops. Phil Trans R Soc Lond. 2003;358:1777–1778.
- Bohan DA, Boffey CW, Brooks DR, et al. Effects on weed and invertebrate abundance and diversity of herbicide management in genetically modified herbicide-tolerant winter-sown oilseed rape. Proc Biol Sci. 2005;272:463-74. doi:10.1098/rspb.2004.3049.
- BBC News. Q&A: GM farm-scale trials. http://news.bbc.co.uk/2/hi/science/nature/3194574.stm. Published March 9, 2004.
- Amos J. GM study shows potential “harm.” BBC News. http://news.bbc.co.uk/1/hi/sci/tech/4368495.stm. Published March 21, 2005.
- Friends of the Earth. Press briefing: Government to publish the final results of the farm scale evaluations of genetically modified crops: Winter oilseed rape. London, UK; 2004. Available at: http://www.foe.co.uk/sites/default/files/downloads/government_to_publish_the.pdf.
- European Parliament and Council. Directive 2009/128/EC of 21 October 2009 establishing a framework for Community action to achieve the sustainable use of pesticides. Off J Eur Union. 2009:71–84.
- Brown A, Ross T. Two GM crops are “worse for wildlife.” The Independent (UK). http://www.mindfully.org/GE/2003/Trials-Threat-Wildlife16oct03.htm. Published October 16, 2003.