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Holzschuh, A., C. F. Dormann, et al. (2011). "Expansion of
mass-flowering crops leads to transient pollinator dilution and reduced
wild plant pollination." <u>Proceedings of the Royal Society B:
Biological Sciences</u> <b>278</b>(1723): 3444-3451.<br><br>
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Agricultural land use results in direct biodiversity decline through loss
of natural habitat, but may also cause indirect cross-habitat effects on
conservation areas. We conducted three landscape-scale field studies on
67 sites to test the hypothesis that mass flowering of oilseed rape
(Brassica napus) results in a transient dilution of bees in crop fields,
and in increased competition between crop plants and grassland plants for
pollinators. Abundances of bumble-bees, which are the main pollinators of
the grassland plant Primula veris, but also pollinate oilseed rape (OSR),
decreased with increasing amount of OSR. This landscape-scale dilution
affected bumble-bee abundances strongly in OSR fields and marginally in
grasslands, where bumble-bee abundances were generally low at the time of
Primula flowering. Seed set of Primula veris, which flowers during OSR
bloom, was reduced by 20 per cent when the amount of OSR within 1 km
radius increased from 0 to 15 per cent. Hence, the current expansion of
bee-attractive biofuel crops results in transient dilution of crop
pollinators, which means an increased competition for pollinators between
crops and wild plants. In conclusion, mass-flowering crops potentially
threaten fitness of concurrently flowering wild plants in conservation
areas, despite the fact that, in the long run, mass-flowering crops can
enhance abundances of generalist pollinators and their pollination
service.<br><br>
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