Some biotech crops have been spectacular failures, leading to lawsuits against biotech companies. For example, in 1997, tens of thousands of acres of biotech cotton withered and died. Similar problems have been seen with other biotech products including rBGH, which some dairy farmers inject into their animals to increase the milk supply. Several U.S. dairy farmer associations and consumer groups have recently taken action to rescind the FDA's approval of this hormone based on its adverse affects to animal and human health. Another risk comes from the fact that biotech farming promotes monoculture, a single crop covering many acres.
Monocultures are notoriously vulnerable to weather events and to insect blights.
Failures can be catastrophic. And they are genetically engineering certain crops to resist Roundup. It's a pretty slick deal. On the one hand, Monsanto sells the Roundup to farmers to kill weeds. On the other hand, it sells a genetically engineered herbicide resistant crop that Roundup can't kill.