The technology used to genetically modify plants is so imprecise that most genetically modified plants are failures - either the inserted genes fail to work or behave in unexpected ways or disrupt the functioning of native genes. Plants that survive the gene transfer process are assumed to be genetically stable and are used to grow GM crops. However, ‘survivors’ are not tested for medium and long-term abnormalities.

Could not the genetic failures inherent in their ‘modification’ only become obvious over time - after the crop is released into the environment and consumed by animals and humans?  As noted by Warwick and Meziani, “Some curious effects are being observed by farmers in the form of unexplained interactions between crops and the animals that eat them (or refuse to eat them).  There are pigs that do not farrow (reproduce) when they are fed on GM grain, the cows, elk and rats that refuse to eat it, the soya plants whose stems split open before the harvest, that fall victim to pests that the farmers have never seen before, that refuse to germinate, and that prove to be highly unstable in successive generations.” 

(See chapter 8 in: Seeds of Doubt - North American farmers´ experiences of GM crops, Soil Association (2002), a report compiled by H. Warwick og G. Meziani.)