Tropes

impactlab_2013 01010.txt

#Three myths about genetically modified crops GM crop technologies have seen dramatic uptake in the past 20 years. It can be hard to see where scientific evidence ends and dogma and speculation begin in the debate over genetically modified (GM) foods and crops. In the almost 20 years since they were commercialized first, GM crop technologies have seen dramatic uptake. Advocates say that they have increased agricultural production by more than US$98 billion and saved an estimated 473 million kilograms of pesticides from being sprayed. But critics question their environmental, social and economic impacts. Researchers, farmers activists and GM seed companies all stridently promote their views, but the scientific data are often inconclusive or contradictory. Complicated truths have long been obscured by the fierce rhetoric.##oei find it frustrating that the debate has moved not on, #says Dominic Glover, an agricultural socioeconomist at Wageningen University and Research center in The netherlands.##oethe two sides speak different languages and have different opinions on what evidence and issues matter, #he says. Here, Nature takes a look at three pressing questions: are GM CROPS fuelling the rise of herbicide-resistant superweeds? Are they driving farmers in India to suicide? And are the foreign transgenes in GM CROPS spreading into other plants? These controversial case studies show how blame shifts, myths are spread and cultural insensitivities can inflame debate. GM CROPS have bred superweeds: True Jay Holder, a farming consultant in Ashburn, Georgia, first noticed Palmer amaranth (Amaranthus palmeri) in a client s transgenic cotton fields about five years ago. Palmer amaranth is a particular pain for farmers in the southeastern United states, where it outcompetes cotton for moisture, light and soil nutrients and can quickly take over fields. Since the late 1990s, US farmers had adopted widely GM cotton engineered to tolerate the herbicide glyphosate, which is marketed as Roundup by Monsanto in St louis, Missouri. The herbicidecrop combination worked spectacularly well#until it didn t. In 2004, herbicide-resistant amaranth was found in one county in Georgia; by 2011, it had spread to 76.##oeit got to the point where some farmers were losing half their cotton fields to the weed, #says Holder. Some scientists and anti-GM groups warned that GM CROPS, by encouraging liberal use of glyphosate, were spurring the evolution of herbicide resistance in many weeds. Twenty-four glyphosate-resistant weed species have been identified since Roundup-tolerant crops were introduced in 1996. But herbicide resistance is a problem for farmers regardless of whether they plant GM CROPS. Some 64 weed species are resistant to the herbicide atrazine, for example, and no crops have been modified genetically to withstand it (see The rise of superweeds). Still, glyphosate-tolerant plants could be considered victims of their own success. Farmers had used historically multiple herbicides, which slowed the development of resistance. They also controlled weeds through ploughing and tilling#practices that deplete topsoil and release carbon dioxide, but do not encourage resistance. The GM CROPS allowed growers to rely almost entirely on glyphosate, which is less toxic than many other chemicals and kills a broad range of weeds without ploughing. Farmers planted them year after year without rotating crop types or varying chemicals to deter resistance. Photo credit: Tumhaber Continue reading Scientific American Share Thissubscribedel. icio. usfacebookredditstumbleupontechnorati F

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