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Unintended Effects of Genetic Manipulation
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Glyphosate-resistant sugar beet production alters population densities of some arthropods, significantly reducing the number of bees and butterflies in beet fields.

Manipulated Organism: Sugar Beet (Beta vulgaris).

Inserted Transgenes: CP4 EPSPS gene from Agrobacterium, which produces an herbicide-resistant version of the enzyme targeted by the herbicide glyphosate (Roundup).

Goal of This Study: From 2000 to 2002, the British government sponsored a series of field trials (the "UK Farm-Scale Evaluations") to determine how the adoption of genetically engineered crops resistant to either glyphosate (Roundup) or glufosinate (Liberty) would impact the abundance and diversity of farmland wildlife. Glyphosate-resistant (GR) sugar beets were part of this study. Each field in the experiment was divided in two, with conventional sugar beets grown on one half and GR sugar beets on the other half.

Results of This Study:
  • The density of weed seedlings was initially four times higher in the GR crop because pre-emergent herbicides were used with the conventional sugar beets. Upon application of glyphosate to the GR sugar beets, however, weed density in the GR fields plummeted. As a result, the amount of weed seed produced in the GR sugar beet fields was three times lower than in the conventional crop.

  • These changes in the weed populations were observed to have significant impacts on some types of arthropods. Butterfly and bee counts were reduced by 25-50% in the GR sugar beet fields, most likely because there were fewer flowering weeds (which provide nectar and pollen) to attract them. Conversely, there were 50% more springtails in the GR sugar beet crop in August, most likely because of the large increase in rotting weeds following the application of glyphosate.

  • Although the impacts on birds were not directly studied, the scientists predicted that the decline in weed seed production observed in the GR sugar beet fields "would markedly reduce important food resources for granivorous farmland birds, many of which declined during the last quarter of the twentieth century" (Gibbons et al., p. 1927).
Additional Comments: For more information about the results of the UK Farm-Scale Evaluations, go to http://www.defra.gov.uk/environment/gm/fse/index.htm

Sources: Heard, M. S., C. Hawes, G. T. Champion, S. J. Clark et al. (2003). "Weeds in Fields with Contrasting Conventional and Genetically Modified Herbicide-Tolerant Crops. I. Effects on Abundance and Diversity," Philosophical Transactions of the Royal Society B vol. 358, pp. 1819-32.

Brooks, D. R., D. A. Bohan, G. T. Champion, A. J. Haughton et al. (2003). "Invertebrate Responses to the Management of Genetically Modified Herbicide-Tolerant and Conventional Spring Crops. II. Within-Field Epigeal and Aerial Arthropods," Philosophical Transactions of the Royal Society B vol. 358, pp. 1863-77.

Gibbons, D. W., D. A. Bohan, P. Rothery, R. C. Stuart et al. (2006). "Weed Seed Resources for Birds in Fields with Contrasting Conventional and Genetically Modified Herbicide-Tolerant Crops," Proceedings of the Royal Society B vol. 273, pp. 1921-28.

Author Affiliations: NERC Centre for Ecology and Hydrology, United Kingdom; Scottish Crop Research Institute; Broom's Barn Research Station, United Kingdom; Rothamsted Research, United Kingdom; RSPB, United Kingdom.

Funding: British Government.

Product Status: As a result of these studies, GR sugar beets were not approved for commercial production in the United Kingdom. Commercial production began in the U.S. in 2008.

Copyright 2009 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/sugarbeet_001.php

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