Glyphosate-resistant sugar beet production alters population densities of
some arthropods, significantly reducing the number of bees and butterflies
in beet fields.
Sugar Beet (Beta vulgaris).
CP4 EPSPS gene from Agrobacterium, which produces an
herbicide-resistant version of the enzyme targeted by the herbicide
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
Results of This Study:
For more information about the results of the UK Farm-Scale Evaluations,
go to http://www.defra.gov.uk/environment/gm/fse/index.htm
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).
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,
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.
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.
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.
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