Fewer wild bees were observed in glyphosate-resistant canola fields.
anola (Brassica napus).
Resistance to the herbicide glyphosate (Roundup) has been engineered into
canola with a combination of two genes: (1) a gene from Agrobacterium
strain CP4 that produces a resistant form of the EPSPS enzyme targeted by
glyphosate, and (2) a modified glyphosate oxidase gene from the bacterium
Ochrobactrum, which accelerates the degradation of glyphosate.
Goal of This Study:
Investigate bee abundance and activity in organic, conventional (non-GM),
and GM canola fields in western Canada.
Results of This Study:
Across the three farming systems, a negative correlation was observed
between bee abundance and "pollination deficit," defined as the
improvement in seed set for hand-pollinated flowers compared with
naturally pollinated flowers. The most bees were collected in the organic
fields (342), which also had the lowest average pollination deficit (7%
more seeds per pod by hand-pollination). The lowest number of bees were
found in the GM canola fields (101), where hand-pollination improved
seed set by 33%. In the conventional canola, 230 bees and an average
pollination deficit of 21% were observed.
A complicating factor in this study was the fact that the canola in the
"conventional and GM fields were different varieties, and therefore
the greater seed deficit in GM fields could have been due to a higher
dependence on pollinators for pollen transfer and seed set than the
conventional variety examined. However, from our data, it seems
unlikely that the conventional canola variety had a lower requirement
for pollinators because at collection sites with low bee abundance,
pollination deficit values were comparable to pollination deficit values
in GM fields with similar pollinator abundances.... Our data suggests
that the low number of pollinators in the GM fields resulted in the high
pollination deficits" (p. 878).
The reduced bee abundance in the GM canola fields could be due to
intrinsic qualities of the plants or the result of management practices.
The authors suggest the latter: "Although insecticide treatments were
similar between GM and conventional fields, GM fields were treated with
Roundup, a highly effective herbicide, which resulted in lower weed
diversity and abundance [and thus less forage for bees] within GM fields
than in conventional fields" (p. 880).
Morandin, L. A., and M. L. Winston (2005). "Wild Bee Abundance and Seed
Production in Conventional, Organic, and Genetically Modified Canola,"
Ecological Applications vol. 15, pp. 871-81.
Simon Fraser University, British Columbia, Canada.
Bayer, Monsanto, the British Columbia Honey Producers Association,
and the Canadian government.
Glyphosate-resistant canola is grown on millions of acres in the U.S. and
Copyright 2009 The Nature