Environmental Impact of Genetically Modified Organisms (GMOs)


The intensification of agriculture has provided cheaper more plentiful food, but has also caused declines in farmland wildlife. The introduction of genetically modified (GM) crops may exacerbate this, or offer new ways of mitigating anthropogenic impacts. The potential consequences of the introduction of GM crops have been studied for over a decade, since commercialization. Although the specific issues depend on the crop and transgenes involved, one common theme that emerges is that the biggest effects will arise from the way in which the GM crop will be managed. Herbicide‐tolerant GM crops may allow better weed control, and this is a risk to biodiversity that should be mitigated. However, even herbicide‐tolerant crops have some environmental benefits through reduced production and application of herbicides. Insect and disease‐resistant crops will have fewer impacts on nontarget organisms than conventional crops and their management, and so may offer direct environmental benefits.

Key concepts

  • Farmland biodiversity has been enhanced and maintained by agricultural land management over hundreds of years. Changes in the intensity of farming since the 1970s have caused its decline, and any future change may exacerbate or ameliorate this impact.

  • Global warming potential (GWP) is the potential of a gas produced by a product or a process to contribute to global warming. It is measured over a specific time period, and on a scale relative to carbon dioxide. Different agricultural practices will have different GWP.

  • Life cycle assessment is defined as an objective process to evaluate the environmental burdens associated with a product or a process by identifying energy and materials used and wastes released to the environment.

  • Meta‐analysis involves retrieving and combining data from a number of studies to obtain a quantitative estimate of the overall effect which can be statistically analysed.

  • Refuge strategy is the strategy employed to delay or prevent the build up of pests resistant to the GM crop. It involves a ‘refuge’ of approximately 20% of the crop in which susceptible individuals may survive, in contrast to the 80% of the crop in which the majority of the pest individuals fail to reach maturity. Any rare resistant individuals that do survive are then likely to mate with a susceptible individual and produce susceptible offspring.

  • Natural enemy release posits that natural enemies limit the growth or survival of plants. Resistance to these natural enemies could release a plant genotype from natural enemy regulation and lead to invasiveness.

  • Comparative sustainability assessment is a matrix‐based approach to assess comparative sustainability, benefits and risks of the introduction of any novel agricultural products or practices. The purpose is to develop a more objective and comprehensive approach towards agricultural and rural policy.

Keywords: GMOs; environmental impact; risk assessment; farmland biodiversity; pesticides

Figure 1.

The mean number of applications of herbicides (±SE) applied during the Farm Scale Evaluations. Data taken from Table 2 of Champion et al. . Figures include pre‐drilling applications and, for spring oilseed rape, desiccants.

Figure 2.

Star plots comparing biodiversity indicators across conventional and GMHT crops. For each indicator, the length of the star corresponds to the value relative to the maximum value found for that indicator in any of the six combinations of crop and treatment (e.g. the maximum values for bees and butterflies were found in conventional spring oilseed rape). The key shows which section of the star diagram represents which indicator. Reproduced from Firbank et al. . www.defra.gov.uk/environment/gm/fse/results/fse‐commentary.pdf. With permission of the Department of the Environment, Food and Rural Affairs.

Figure 3.

In bioremediation, plants and bacteria may work in consortia to degrade xenobiotics. Plants may take up the by‐products of metabolism of bacteria, they may also selectively support indigenous degrading bacteria in their rhizosphere. Reproduced from Macek et al. . With permission from Elsevier.



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Further Reading

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Hails RS and Morley K (2005) Genes invading new populations: a risk assessment perspective. Trends in Ecology & Evolution 20(5): 245–252.

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Hails, Rosemary S(Sep 2009) Environmental Impact of Genetically Modified Organisms (GMOs). In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0003255.pub2]