http://news.scotsman.com/scitech.cfm?id=306362005
Scientific study finds GM crops inhibit weeds affecting natural food chain

Government-commissioned scientists compared GM winter-sown oilseed rape with a conventional version of the crop, and found that fewer broad leaved weeds and their seeds were present in fields where the GM herbicide-tolerant oilseed rape was grown. Flowers of such weeds are important as food for insects, while the seeds are a major source of sustenance for farmland birds.