There's a serious and potentially devastating potential (beginning to make itself felt already, actually) that GMO crops will reduce our ability to feed ourselves at all.
GMO companies PROMISED that (a) there would be no harm to the environment and (b) no harm to other crops (same species or different species) and that's just not been the case. It's already been mentioned that GMO crops cross-pollinate with non-GMO crops nearby (and Monsanto had the temerity to sue a victimized Canadian farmer because of it!!) This means that we may not be able to keep GMOs from polluting any of our crops -- and frankly, if they can polluty ANY, they shouldn't IMO be used).
Further, it's been well-established that GMO crops (forget which one) have harmed the Monarch butterfly by decimating its populations.
Even scarier, in terms of what we may be doing to our future ability to feed ourselves, thanks to GMO corn and cross-pollinization, we are in danger of losing our original, millennia-old stocks of maize in the very region where maize first developed.
Finally, effects on humans hasn't been fully determined. There are many suspicions of ill health effects on humans. Here's just one recent article:
http://www.mg.co.za/Content/l3.asp?ao=31845Scientists investigating a spate of illnesses among people living close to GM maize fields in the Philippines believe that the crop may have triggered fevers, respiratory illnesses and skin reactions.
If preliminary results are confirmed, it would be one of the first recorded cases of serious health problems associated with GM crops, and could damage the reputation of the biotech agriculture industry, which is rapidly expanding in developing countries.
The scientists' findings were immediately challenged by Monsanto, the world's leading GM company, and by the Philippine government.
The concern surrounds an unnamed village in northern Mindanao, where 39 people living near a field of Bt maize -- which contains a pesticide in the gene -- started suffering last autumn when the crop was producing pollen.
Doctors thought they had an infectious disease, but when four families left the village and recovered, and then showed the same symptoms on return, an environmental cause was suspected.
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So, do we really want to fool with Mother Nature, or "God's plan"? Given the facts on the ground, that sounds like a pragmatic argument to me, tho one with definite moral considerations given the greed factor of Monsanto and other GM companies vis a vis the damage being done to the planet and her people.