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Gm Crops Good For Environment Study Finds Too Much Homework

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Are GM crops good or bad for the environment?

Unfortunately there's no easy answer to this, since it often depends on the crops and how they're used.

In some cases, GM crops can help farmers use fewer chemical insecticides. In others, they might lead to greater herbicide use or pesticide resistance. On balance, many scientific bodies are unconvinced that GM foods pose a special environmental threat — so long as they're used carefully.

Here's what the National Research Council concluded in 2010: "Generally, GE crops have had fewer adverse effects on the environment than non-GE crops produced conventionally." But the report cautioned, "Excessive reliance on a single technology combined with a lack of diverse farming practices could undermine the economic and environmental gains from these GE crops."

Some GM crops allow fewer pesticides: In some cases, GM crops can benefit the environment. Cotton that's engineered to be pest-resistant can allow farmers to use fewer chemical pesticides. Likewise, the growth of Bt corn in the United States since 1996 has allowed farmers to use fewer insecticides in cornfields:

(Science)

Other GM crops can lead to more herbicides — with a caveat: The story is murkier for chemical herbicides used on weeds. Many crops like soy, corn, cotton, and canola are now genetically engineered to be resistant to Roundup, a weed killer. That has led toa clear increase in herbicide use in the United States. But there's a caveat here: the herbicide behind this increase, glyphosate, is less toxic than some of its predecessors.

Pest resistance and the risk of overuse: The National Research Council also warned against improper use of GM technology: Farmers who plant herbicide-resistant GM crops often use a limited range of herbicides on their fields, which can give rise to herbicide-resistant "superweeds." Similarly, there's evidence that overplanting of Bt cornhas fostereda new breed of resistant insects in some fields.

That said, many conventional crops also require herbicides, and those "superweeds" can appear on non-GM crop sites, too. In the end, the National Research Council wasn't convinced that GM crops were inherently riskier, so long as they were used properly.

Other risks: It's worth listing a few other environmental concerns, as well. The decline of the monarch butterfly in North America has been linked to the increased use of herbicide spraying on herbicide-tolerant crops. There's also the risk that genetically engineered traits still in the testing phase could escape into nature, as apparently occurred in May 2013, when a never-approved strain of GM wheat made its way to an Oregon field.

Among the winners in this month’s elections, along with the Republican candidate in just about every competitive race, were foods containing genetically modified organisms. Ballot initiatives that would have mandated the labeling of GMOs on store shelves lost in both in Colorado (overwhelmingly) and Oregon (narrowly). Nobody knows exactly how the passage of those measures would have affected the sales of GMO products over the long run; consumers have shown a tendency to ignore the calorie counts on food labels.

Still, it’s possible that over the short term labeling laws would make foods containing GMOs less popular and therefore decrease the amount of farmland, in the U.S. and abroad, given over to modified crops. That was the goal of many labeling proponents, and a new study suggests it would have been a bad result.

The study doesn’t look at the health effects of GMOs. Thousands of independent studies have already done so and found that GMOs are perfectly safe to eat. The new research instead looks at the costs and benefits for agriculture and the environment, a question on which there is less consensus. Plenty of research, including this large study from the National Academy of Sciences, has found that GMOs have significantly increased farm yields while decreasing pesticide use and soil erosion. The idea is that because GM crops are engineered to produce insecticides in their tissues or to be immune to particular herbicides, they reduce the man-hours, fuel, and chemical inputs in farming, even while reducing losses to pests and weather. (Anti-GMO groups have looked at the same data and argued that the yield gains are minimal (PDF) and limited to special circumstances.)

The new study, in the journal PLOS One, comes down strongly on the pro-GMO side. It’s a meta-analysis that aggregates and examines the results of 147 existing research studies looking at GM soybeans, maize and cotton, the world’s biggest GM commodity crops. The authors, a pair of agricultural economists at Germany’s University of Göttingen, found that GM technology increased crop yields by 22 percent, reduced pesticide use by 37 percent, and increased farmer profits by 68 percent.

A few details jump out from the study. For one, the benefits were greater in those GM crops that produced their own pesticides rather than those engineered for herbicide resistance—the latter trait has been hugely convenient for farmers, but has also shown a greater rebound effect as weed species evolved resistance to the chosen herbicides.

The yield and profit gains were also greater in developing countries than in developed countries. Finally, the studies in the meta-analyses that were published in peer-reviewed journals showed more dramatic effects, both in yield and profit gains, than those published elsewhere. Put another way, the more rigorously vetted a study, the more likely it has been to find benefits for GMOs.

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