For GSS Ecosystem Change chapter 4. Excerpt: Faltering under extreme
weather and vanishing habitats, the yearly winter migration of monarch
butterflies to a handful of forested Mexican mountains dwindled
precipitously in December, continuing what scientists said was an
increasingly alarming decline. ...Mexico is the southern terminus of an
age-old journey in which monarchs shuttle back and forth between
far-flung summertime havens in Canada and the United States and a single
winter home in Mexico’s Sierra Madre mountains. ...The latest drop is
best explained by a two-year stretch of bad weather, said Chip Taylor, a
biologist at the University of Kansas.... But while good weather may
help the monarchs rebuild their numbers, their long-term problem — the
steady shrinking of habitat along their migratory route — poses a far
greater danger. The monarchs’ migratory freeway runs through the Great
Plains. As they flew north from Mexico in early 2012, Dr. Taylor said,
months of near-record heat sapped their endurance and skewed their
migratory patterns in ways that limited their ability to reproduce. Last
spring, he said, the opposite happened: Unusual springtime cold in
Texas delayed the butterflies’ northward migration, causing them to
arrive late in areas where they would normally have bred weeks earlier.
...Monarchs lay their eggs only on milkweed, and patches of the plant
have rapidly disappeared from the Great Plains over the last decade. As
corn prices have risen — spurred in part by a government mandate to add
ethanol to gasoline — farmers have planted tens of millions of acres of
idle land along the monarchs’ path that once provided both milkweed and
nectar. ...The monarchs are but the most visible victims of the habitat
loss, Dr. Oberhauser said. A wide variety of pollinators and other
insects, including many that are beneficial to farmers, are also
disappearing, she said, along with the predators that feed on them.... http://www.nytimes.com/2014/01/30/us/monarch-butterflies-falter-under-extreme-weather.html. Michael Wines, The New York Times. |
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