Dear Max
I would disagree with you over the biodiversity issue. If uptake of GM crop is uniform then that is the major problem not whether genes spread around because genes have been spreading around ever since mankind started agriculture and selected out certain plants for farming. Genetic monocultures are easily subject to disease spread and that represents a major issue but is not one unique to GM crops. Southern leaf corn blight was the result in the 1970's of using limited genetic material. I signed a protocol some while back to protect nature and wildlife by ensuring that agriculture was the most efficient that could be attained. The problem areas in the world are places where population still increases rapidly. In mexico home of green revolution wheat an estimated 1.5 million hectares of forest are cut down every year to expand peasant farming and accomodate more people. This form of farming is called extensive farming because it rapidly exhausts the soil of minerals and thus the process of forest felling continues to provide new farms and soil for exploitation. Now this ought to be the sort of place where technology can help but the mexican government has placed extreme restrictions on anything to do with GM so that knowledge is abandoned.
The major problems with food and population are political not scientific. Most farming around the world receives subsidies of one sort of another because of its importance in feeding the population. At the end of the day can you put a value on human life particularly if it is your own? So unless you can value human life in dollars then it is impossible to say whether GM crops provide value for money. I have often heard the argument that if you provide more food then populations increase. Untrue of course in the west because there are many factors that determine population numbers although starvation is an ultimate controller. Starvation is described as the worst torture that can be inflicted on anyone. As for GM consumption well in europe we have labelling so people can avoid it if they wish but studies have indicated that no-one looks.
Kind regards
TonyDear Professor Trewavas,
As far as biodiversity, I was referring to a hypothetical risk: if the transgenes that spread in the wild confer an adaptive advantage, unaffected varieties would be supplanted. This would first of all reduce biodiversity in an absolute sense, and secondly create a kind of inadvertent monoculture, with potentially disastrous results. [E.g., if every remaining variety of maize depended on the expression of Bt, and pests acquired Bt resistance]. Conversely, a similar problem could occur if the transferred genes conveyed an adaptive disadvantage, as in the case of GM Salmon, as discussed by Muir and Howard (with commentary by Hackett) in Transgenic Research 11 (2002). I understand that these risks are both hypothetical and attached to all genetic transfer, whether or not "engineered" by humans. But since we are engineering gene transfer, it behooves us to consider very carefully the potential ramifications thereof.
Research in historical demography has shown that early modern European societies adjusted their population size in response to economic conditions by changes in marriage patterns [a recent summary is Jan de Vries, "Population," in Thomas A. Brady, jr., Heiko O. Oberman, and James D. Tracy, eds., Handbook of European History, 1400-1600, Vol. I (Leiden, 1994), pp. 1 - 50] -- the implication is that human society can be flexible enough to adjust itself before starvation does it for us. We now have the technology to change birthrates more directly, and I do not see why this approach to the problem of population growth is less valid than adjusting the food supply (the other half of the Malthusian equation) by whatever means. Not to say that the latter is intrinsically invalid, but I do not understand why 10 billion people is desirable (an article in the NY times today discusses the speculative nation of population growth forecasts: http://www.nytimes.com/2002/08/20/science/earth/20POPU.html).
The root issue with GM food, as I see it, is that it is going to have a profound effect on human society and its environment for millennia, as you noted in the Nature article. It is too important to be left to ideologues in either camp, but most people are oblivious, indifferent, or incapable of understanding the issues. Our exchange has spurred me to learn more about them (within the limits of my sad scientific education), change some prejudices, and consider more carefully what I really believe, and why. Some of your earlier articles [1, 2 -- cf. 3] on the problems with extensive, particularly organic, agriculture, for example, significantly altered some of my preconceptions. But the debate about GM technology needs to be stripped of posturing and released from the friendly, but narrow, confines of Nature. I fear that it won't happen.
Sincerely,
Max
