GM Crops Are Killing Monarch Butterflies, After All [View all]

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—By Tom Philpott| Wed Mar. 21, 2012 10:00 AM PDT

If any insect species can be described as charismatic minifauna, it's the monarch butterfly. The gorgeous creatures flutter about in a migratory range that stretches from the northern part of South America up into Canada. The monarch is the only butterfly species that undertakes such a long-distance migration. And when they alight upon a place en masse, heads turn. No fewer than five states—Texas, Alabama, Idaho, illinois, and Minnesota—claim the monarch as their state insect.

Unfortunately, the monarch populations appear to be in a state of decline. Why? A new study (abstract; press release) from University of Minnesota and Iowa State University researchers points to an answer: the rapid rise of crops engineered to withstand herbicides.

Their argument is powerful. Monarchs lay their eggs on one particular kind of plant: the milkweed. And when the eggs hatch, the caterpillars feed exclusively on the weed. Milkweed is common throughout the Midwest, and has long thrived at the edges of corn fields. But when Monsanto rolled out its "Roundup Ready" seeds in 1996, which grew into plants that could thrive amid lashings of its flagship Roundup herbicide, the Midwest's ecology changed. As farmers regularly doused ever-expanding swaths of land with Roundup without having to worry about the hurting their crops, milkweed no longer thrived—and as a result, the charismatic butterfly whose caterpillars require it can no longer thrive, either.

The researchers estimate that the amount of milkweed in in the Midwest plunged by 58 percent from 1999 to 2010, pressured mainly by the expansion of Roundup Ready genetically engineered crops. Over the same period, monarch egg production in the regions sank by 81 percent. And it turns out that monarchs tend to lay more eggs milkweeds that sprout up in and around cultivated fields. So when farmers snuff out the milkweeds with Roundup, they're exerting a disproportionate effect on monarchs.
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http://motherjones.com/tom-philpott/2012/03/researchers-gm-crops-are-killing-monarch-butterflies-after-all