Most GM work in plants is beneficial, but some is just poorly thougth out--with is what I think Pellidon is trying to get across.
Think of this. You take a gene for resistance to a pesticede and insert it into the food crop. The idea is that now you can spray *everything* with RoundUp (or some similar brand of pesticide) and the food crop will survive and the weeds will die resulting in higher yields and higher purity (What, you didn't think that everything that ends up ground into your flower was wheat, did you?). The problem comes in with the tendency of plants to swap genes around *amongst* different plants. So, now you have pesticide resistant weeds in a few years. Great, now what do you do about the weeds? More to the point, what does your neighbor do? And, what does the rest of the public do now that you're spraying *much more* pesticide than you used to?
To give some background (I'm from the sticks, don't 'cha know), there are a few ways to kill weeds. One is to use a targeted pesticide, but those tend only to kill of a very narrow family of weeds and the plants become resistant fairly quickly (here, we're talking quick in evolutionary terms, so a dozen generations or less). The other way is to selectively apply a more broad spectrum pesticide--like RoundUp. You do it 'selectively' in whatever way is practical. In beans--what are sensitive to it--they use a trick that since the weeds grow more quickly(that's how they choke out the other plants--getting to the sun first) they tend to be taller. So, run a bar holding a rope soaked in herbicide over the crop but set at a height higer than the beans and lower than the weeds. You apply to only the weeds. Yeah!
One other method is to use a 'bean buggy'. It's a device towed behind a tractor with seats for poorly paid kids to sit on and spray the weeds with little sprayers. Sure, you get the weed, but you get the few plants around it, too. So, it's not as well targeted as the bar, but it's more effective.
Which to use is a tradeoff for the farmer to make. While we're on the topic of farmers making good business decisions, let's debunk the myth of profit margin and GM seeds. Most farmers (modern ones) are quite schrewd fellows and will run all of the numbers on GM seeds before they commit to it. They won't do it if they don't think it'll make them money.
The down side to that is the fact that there may be some costs that they miss (du-ah). These can be things like the neighbor using GM weed resistant crops and causing *our* weeds to become more resistant causing *us* to pay more to kill them. Things like that.
Did I miss anything? /ubbthreads/images/graemlins/smile.gif