If gene flow occurs, are negative ecological impacts inevitable?
Looking at the experience gained from growing conventionally bred crops for many decades, it seems that very rarely, if ever, will gene flow from a crop to a wild relative have a significant ecological impact. Gene flow from a conventional crop to a wild, weedy relative has been documented. In a few instances, the new genes have had a negative impact on crop management because controlling the hybrid weed growing in fields of the conventional, related crop became more difficult. However, adverse effects on agricultural systems should be distinguished from negative impacts on natural ecosystems. Past gene flow from conventional crops to wild, native plants appears not to have had a noticeable impact on natural ecosystems. In order to have negative environmental effects, the gene must become widespread in the wild plant population and give the wild plants possessing the crop genes a competitive advantage over those without the crop genes.
