Sarah Zhang’s defense of genetically modified (GMO) crops in Mother Jones purports to make the scientific case for the safety and environmental benefits of GMOs. It’s an easier case to make when one focuses solely on one GMO variety, as Zhang does, while ignoring the majority of GMOs grown worldwide. Zhang writes only about the GMO insect resistant “Bt” crops, which she fails to note comprise just 15% of the global GMO acreage.
Ignoring the adverse effects from the other 85% of GMO acreage is hardly a “scientific” approach, but considering the impact of GMO crops broadly would undermine her argument.
Zhang’s one point in favor of GMO crops is their impact on pesticide use: “Even critics will acknowledge that Bt crops have led to a sharp decrease in insecticide use, which is a huge net positive for the environment,” she claims.
But the “huge net positive” from Bt GMO crops is more than offset by the predominant GMO variety, crops engineered to withstand mega-doses of pesticides. These GMO “herbicide tolerant” crops account for nearly 60% of all GMOs grown worldwide. How many more tons of pesticides are used as a result of all GMO crops? A 2009 analysis of USDA pesticide data by agricultural scientist Charles Benbrook (one of Zhang’s sources) found that pesticide use from the adoption of all GMO crops in the US has put 318 million additional pounds of chemicals on our food and into the environment. That’s some “net positive”! Given the recent rapid increase in superweeds from GMO crops –and the accompanying use of even more toxic pesticides to deal with the weeds–the burden of pesticides due to GMOs has surely grown even more since this analysis was published.
Even if some do concede the short-term benefits of Bt crops, no one believes the crops will remain sustainable. Monsanto, the leading biotech crop maker (and the global supervillain responsible for progressive’s “unscientific” response to GMOs, according to Zhang) told New York Times writer Michael Pollan in 1998 that insect resistance to Bt crops would not occur for thirty years. Five years later, scientists confirmed the first field resistance from Bt crops, in a study that found a dozen examples of resistant bugs in Bt fields between 2003 and 2006.
As MoJo’s Tom Philpott reported last year, Monsanto continues to deny the superbug problem, despite confirmed or suspected resistance in seven states. Moreover, a 2010 study in Nature found that GMO cotton in China has merely displaced the targeted pest for a new equally damaging insect, suggesting that GMOs create the same “pesticide treadmill” that has kept farmers dependent on the pesticide industry’s unsustainable and toxic products for decades.
Aside from the resistance issue, GMO Bt crops do not, as Zhang implies, replace all insecticides. Bt crops target only certain bugs, so farmers continue to spray GMO crops for many other insects. More than a decade after the widespread introduction of GMO cotton, insecticides used on cotton remain by far the highest of any crop, accounting for 16% of all insecticides used worldwide. And as the above mentioned 2008 paper found, Bt crops alone don’t even control the targeted insects without additional chemical help: as the authors noted, other toxic insecticides “…have been used from the outset to augment control of (the targeted insect) H. zea on Bt cotton because (the GMO Bt variety) alone is not sufficient to control high-density populations of the pest.”
Resistance to Bt crops is not merely a public relations problem for Monsanto. Zhang describes the crops as if Bt was manna brought down from heaven by the biotech industry, but natural Bt sprays have been used safely by farmers for decades. The natural insecticide is so benign that organic farmers are permitted to use them, though only as a last resort and under strict guidelines. Consider then what happens when neighboring GMO farms create resistant insects: the nearby organic farmers last line of control, a Bt spray, will be useless – while the conventional farmer across the fence will simply go back to the more toxic chemical alternatives. One scientist studying Bt resistance created by GMO crops called this possibility “a particularly threatening scenario” for organic farmers. It’s hard to see how crippling organic agriculture while forcing farmers to return to older, more toxic pesticides can be a “net positive” for the environment.
Finally, Zhang notes that it’s possible that both GMO crops and reliance on pesticides could be eliminated with sustainable farming, but complains that “there are no large-scale studies proving this.” She must not be looking too hard. In 2000, in what was one of the largest agricultural experiments ever, thousands of rice farmers in China replaced their monocrop fields with diverse rice varieties, a simple sustainable technique, and using no chemicals or GMOs saw yields rise by 18% overall, with one diverse array of mixed rice varieties resulting in a yield gain of 89%. The authors noted that the diverse “mixed (rice) populations produced more total grain per hectare than their corresponding monocultures in all cases.”
Another report from the University of Essex involving 208 sustainable and/or organic farming projects from 52 countries showed increases in food production over more than 70 million acres and found nearly 9 million households benefited from increased food production and consumption. More recently, a 2008 report overseen by agricultural scientist and World Food Prize winner Hans Herren looked at global agricultural development in light of growing populations, and called for organic, agroecological approaches to address hunger and food inequities. In an interview on the report, Herren noted that “there is evidence from the field for now over three decades that sustainable agriculture cannot only nourish the world, but can do so for the long haul,” and called organic and sustainable techniques “the only approaches” for long-term food production. These fields, he noted in another interview, will produce the kind of science that will truly support the small farmers globally who produce most of the world’s food.
But of course, that’s just anti-science, anti-GMO propaganda – not Sarah Zhang’s rigorous scientific analysis.