Pollinators such as bees can pick up pollen from GE plants and carry it for several miles, cross-pollinating even distant conventional crops. There is no way to control this type of cross-pollination. A study in 1999 reported that researchers planted a field of sterile oilseed rape plants up to two-and-a-half miles away from a crop of GE oilseed rape. Since the test plot plants were all sterile, any seeds produced must have been the result of cross-pollination from the GE field. The scientists found that 5 percent of the flower buds on the test plants were pollinated. Related to genetic pollution is the drifting of pesticides sprayed on fields with pesticide resistant crops to fields planted in conventional crops. Products like Roundup can drift to neighboring fields not planted with Roundup-resistant soybeans and kill those soybeans. This forces the farmer not using that technology to switch to it.
Genetic material is often and easily transferred between living organisms. Critics of food biotechnology fear that herbicide-resistant GE crops will eventually pass on those resistance traits to the very weeds and pests to which they were engineered to be superior, creating “superweeds” and “superpests.” It will be necessary to use higher and higher doses of chemicals to control these “superweeds.” Anti-GE literature cites studies showing that herbicide-resistant rapeseed (canola) spreads resistance properties to wild mustard plants.
As a natural course of events, weeds and insects (and bacteria for that matter) eventually develop resistance to the chemicals used to control them. Because farmers will be using Roundup more and more, weeds will develop resistance to it sooner. Opponents fear that it will be necessary to apply more and more Roundup until finally it won't be effective at all, and farmers will have even fewer choices to combat weeds in their fields. Another example of this danger is the case of Bacillus thuringiensis (Bt), a soil bacterium that produces a natural toxin that organic farmers use as a method of biological pest control. The toxin in naturally occurring Bt bacteria are only activated by enzymes in the digestive tract of certain insects, notably caterpillars. Crops have now been produced that have the gene for the Bt toxin, giving them a built-in insecticide. While in the past farmers have only occasionally applied the Bt toxin when they had an infestation, the Bt toxin in the GE crops is produced all the time. Therefore, insects are continually exposed to the Bt toxin, which speeds up the time in which they will develop resistance to Bt. Scientists who believe that some insects have already developed Bt resistance predict that within three to five years most target insects will be resistant to Bt. There is also concern that the Bt toxin in the GE crops is of a slightly different form than the natural toxin, and that it may harm a wider range of insects, including some that are beneficial. Since the understanding of molecular genetics is still in its infancy, some researchers fear that gene splicing will inevitably result in unanticipated and dangerous surprises. They are exploring whether genetically altering plants to withstand certain viruses and pathogens will cause those viruses and pathogens to mutate into new and/or stronger forms. In the same way that the introduction of exotic species into an environment tends to cause the decline of the native species, introducing GE plants into an environment may eventually overpower the native species. As an example, opponents hypothesize that if GE salmon that are bigger and hardier than the wild varieties are released into habitats, they will out-compete those wild varieties and cause their extinction. This genetic bio-invasion could set off a whole chain of environmental events not yet dreamed of.
