Ecological Impacts of Herbicides Companies affirm that bromoxynil and glyphosate, when properly applied degrade rapidly in the soil, do not accumulate in groundwater, have no effects on non-target organisms and leaves no residues in food. There is, however, evidence that bromoxynil causes birth defects in laboratory animals, is toxic to fish and may cause cancer in humans. Because bromoxynil is absorbed dermally, and because it causes birth defects in rodents, it is likely to pose hazards to farmers and farm workers. As this herbicide is known to accumulate in fruits and tubers suffering little metabolic degradation in plants, questions about food safety also arise. The biological process of concern here is introgression, that is, hybridization among distinct plant species.
Evidence indicates that such genetic exchanges among wild, weed and crop plants already occur.
This is worrisome given that a number of US crops are grown in close proximity to sexually compatible wild relatives. HRCs will most probably enhance continuous cropping by inhibiting the use of rotations and polycultures susceptible to the herbicides used with HRCs. Such impoverished, low plant diversity agroecosystems provide optimal conditions for unhampered growth of weeds, insects and diseases because many ecological niches are not filled by other organisms. According to the industry, the promise of transgenic crops inserted with Bt genes is the replacement of synthetic insecticides now used to control insect pests. Bt crops can starve natural enemies as these beneficial insects need a small amount of prey to survive in the agroecosystem.