Scientists agree that there is only a very low risk of domesticated crops becoming weeds themselves because the traits that make them desirable as crops often make them less fit to survive and reproduce in the wild (ICSU, GM Science Review Panel). Weeds that hybridize with herbicide-resistant crops have the potential to acquire the herbicide-tolerant trait, although this would only provide an advantage in the presence of the herbicide (ICSU, GM Science Review Panel). According to the GM Science Review Panel, "Detailed field experiments on several GM crops in a range of environments have demonstrated that the transgenic traits investigated - herbicide tolerance and insect resistance - do not significantly increase the fitness of the plants in semi-natural habitats" (GM Science Review Panel, 2003:19). More evidence is required regarding the effect of fitness-enhancing traits on invasiveness (GM Science Review Panel).