As recently as a decade ago, farms in the Midwest were commonly marred — at
least as a farmer would view it — by unruly patches of milkweed amid the neat rows of
emerging corn or soybeans.
Not anymore. Fields are now planted with genetically modified corn and soybeans
resistant to the herbicide Roundup, allowing farmers to spray the chemical to eradicate
weeds, including milkweed. And while that sounds like good news for the farmers, a
growing number of scientists fear it is imperiling the monarch butterfly, 11
spectacular migrations make it 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, and
their larvae eat it. While the evidence is still preliminary and disputed, experts like Chip
Taylor say the growing use of genetically modified crops is threatening the
orange-and-black butterfly by depriving it 12 its habitat.
The major 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 13 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, 14 the decrease partly to the loss of milkweed from
use of “Roundup Ready” crops. Other causes, it says, are the loss of milkweed to land
development, illegal logging at the wintering sites in Mexico, and severe weather. The
study does not suggest the monarch 15 extinct. But it questions whether the annual
migration, the impetus for butterfly festivals around the United States and waves of
tourism to Mexico, is sustainable. 【題組】13. (A) sarcastically (B) statistically (C) primarily (D) similarly
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