The production of transgenics represents a danger to the natural biodiversity of the treated plants and animals, since genetic manipulation could alter ecosystems, causing irreversible damage, even reaching such a degree as to cause possible extinction.
It should be considered under what parameters these practices are feasible, without prejudice to the natural balance of plant and animal species, beyond commercial purposes.
Yes I agree GMO plants and all organisms might be a risk to environemnt and biodiversity. However, we can create them in such way that they for example will not be fertile - thus preventing the "contamination" of ecosystem. But yes, we should be cautious. I think that with all that is going on all around the world - deforestation, global warming, pollution - GMO plants are actually quite harmless in comparison.