IT CERTAINLY seems like a good idea. Plant a crop genetically modified to be resistant to a broad-spectrum herbicide like glyphosate, and you can wipe out all the weeds with a couple of applications of the chemical. There is no need even to plough the fields before planting, which reduces soil erosion and the amount of carbon released to the atmosphere.
Unfortunately, things aren鈥檛 that simple. Seeds left in the fields from the previous season鈥檚 crop will turn up as unwanted 鈥渧olunteers鈥� that can only be killed with a different herbicide. And after a few seasons of growing the same crop in the same field weeds that are naturally resistant to the main herbicide will start to take over, again forcing farmers to resort to other weedkillers.
In North America, these problems have proved to be irritants rather than show stoppers. But further south, the picture is different. In the late 1990s, farmers in Argentina leapt at the opportunity to grow herbicide-resistant soya. Today, as volunteers and superweeds emerge, some are reportedly fighting them off with quantities of herbicides that are destroying neighbours鈥� crops and making people sick. Although the full picture is not clear, even Argentinian advocates of GM crops admit that today鈥檚 farming methods cannot be sustained (see 鈥淎rgentina鈥檚 bitter harvest鈥�).
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All of this will be seized upon by some campaigners as proof that GM crops are plain bad. But the real story is more complex. For one thing, any farmer who sprays herbicides with such abandon that nearby crops and people are affected is being reckless and should face legal penalties. Moreover, pesticide poisoning is nothing new and we know that other GM crops, such as Bt cotton have actually reduced instances of it in countries such as China (see New 杏吧原创, 18 May 2002, p 44).
Argentina鈥檚 troubles are caused more by a mishandling of the technology than by the technology itself. Turning over large areas of farmland to just one crop, relying on one method of weed control, and failing to take precautions such as rotating crops, is asking for trouble.
But if opponents of GM crops should pause before seizing on Argentina鈥檚 example, so should proponents who claim GM crops will be a boon to farmers in developing countries. Unless government agencies and seed companies ensure that farmers grow GM crops in the right way, their value will not last long. For example, farmers planting Bt cotton in South Africa boast that they do not need to plant 鈥渞efuges鈥� of traditional cotton nearby. This may be true today, but pests resistant to Bt will evolve faster if they do not.
As for Argentina, the question now is what will the country鈥檚 farmers do next?