- GE crops can interbreed with wild relatives which can create weeds that are more aggressive and/or resistant to herbicides. Beyond the risk of bioengineered plants exchanging genes with neighbors, the continued use of a single herbicide creates selective pressure for weeds to stumble upon the genetic combination for resistance traits. This may already be occurring in creeping bentgrass (Watrud et al. 2004), sunflower (Snow et al. 2003), and others (Chapman & Burke 2006).
- To date, the Bacillus thuringiensis toxin expressed in GE plants has been shown to negatively affect other organisms in the food chain, including monarch butterfly larvae (Lossey et al. 1999), green lacewings (Hilbeck et al. 1998), and ladybirds (Schmidt et al. 2009).