“Research published by Environmental Sciences Europe last year that showed pollen from GM maize could travel up to three km, one hundred times further than the 30 meters established by the EFSA [European Food Safety Authority] in 2011.” (http://uk.reuters.com/article/2015/07/02/us-eu-gmo-efsa-idUKKCN0PC22W20150702)

Since butterflies can travel further than 3km and therefore easily avoid the GM pollen, the 30m buffer zone is purely for one-legged beetles.