The monarch butterfly Danaus plexippus is one of the most beloved of insects — “the Bambi of the insect world,” as an entomologist once put it. Monarchs lay their eggs on milkweed Asclepiadaceae, and their larvae eat it. Dr. Chip Taylor, an insect ecologist at the University of Kansas and director of the research and conservation program Monarch Watch, says the growing use of genetically modified crops is threatening the orange-and-black butterfly by depriving it of habitat. “This milkweed has disappeared from at least 100 million acres of these row crops”.
The primary evidence that monarch populations are in decline comes from a new study showing a drop over the last 17 years of the area occupied by monarchs in central Mexico, where many of them spend the winter. The amount of land occupied by the monarchs is thought to be a proxy for their population size.
“This is the first time we have the data that we can analyze statistically that shows there’s a downward trend,” said Ernest H. Williams, a professor of biology at Hamilton College and an author of the study along with Dr. Taylor and others.
The paper, published online by the journal Insect Conservation and Diversity, attributes the decrease partly to the loss of milkweed from use of “Roundup Ready” crops. Genetically modified corn and soybeans resistant to the herbicide Roundup allow farmers to spray the chemical to eradicate weeds, including milkweed.
Source: The New York Tmes, 11 July 2011
http://www.nytimes.com/2011/07/12/science/12butterfly.html
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