Butterfly numbers were cut by up to two-thirds and bee populations by half in fields of transgenic winter oilseed rape (canola), according to the final results of a three-year study commissioned by the UK government. Researchers behind the £6-million (US$11-million) study said that the project’s weed-control system is to blame.
We evaluated the effects of the herbicide management associated with genetically modiﬁed herbicidetolerant (GMHT) winter oilseed rape (WOSR) on weed and invertebrate abundance and diversity by testing the null hypothesis that there is no difference between the effects of herbicide management of GMHT WOSR and that of comparable conventional varieties. For total weeds there were few treatment differences between GMHT and conventional cropping, but large and opposite treatment effects were observed for dicots and monocots. In the GMHT treatment, there were fewer dicots and more monocots than in conventional crops. At harvest, dicot biomass and seed rain in the GMHT treatment were one-third of that in the conventional, while monocot biomass was threefold greater and monocot seed rain almost ﬁvefold greater in the GMHT treatment than in the conventional. These differential effects persisted into the following two years of the rotation. Bees and butterﬂies that forage and select for dicot weeds were less abundant in GMHT WOSR management in July. Year totals for Collembola were greater under GMHT management. There were few other treatment effects on invertebrates, despite the marked effects of herbicide management on the weeds.
David A. Bohan, Caroline W. H. Boffey, David R. Brooks, Suzanne J. Clark, Alan M. Dewar, Les G. Firbank, Alison J. Haughton, Cathy Hawes, Matthew S. Heard, Mike J. May, Juliet L. Osborne, Joe N. Perry, Peter Rothery, David B. Roy, Rod J. Scott, Geoff R. Squire, Ian P. Woiwod and Gillian T. Champion.