Friday, March 7, 2014
By Mark Stevenson
The Associated Press
MEXICO CITY — The number of Monarch butterflies wintering in Mexico plunged this year to its lowest level since studies began in 1993, leading experts to announce Wednesday that the insects’ annual migration from the United States and Canada is in danger of disappearing.
A Monarch butterfly perches on a tree at the Sierra Chincua Sanctuary in the mountains of Mexico’s Michoacan state. A report blames the dramatic decline of the butterfly’s numbers on the loss of habitat in Mexico’s mountaintop forests and the massive displacement of its food source, the milkweed plant, in the U.S.
The Associated Press
Monarch butterflies gather on a tree at the El Rosario Butterfly Sanctuary near Angangueo, Mexico. Extreme weather – extreme cold snaps, unusually heavy rains or droughts in Canada, the United States and Mexico – have apparently contributed to the butterfly’s decline.
The Associated Press
A report released by the World Wildlife Fund, Mexico’s Environment Department and the Natural Protected Areas Commission blames the displacement of the milkweed the species feeds on by genetically modified crops and urban sprawl in the United States, as well as the dramatic reduction of the butterflies’ habitat in Mexico due to illegal logging of the trees they depend on for shelter.
After steep and steady declines in the previous three years, the black-and-orange butterflies now cover only 1.65 acres in the pine and fir forests west of Mexico City, compared to 2.93 acres last year. They covered more than 44.5 acres at their recorded peak in 1995.
Because the butterflies clump together by the thousands in trees, they are counted by the area they cover.
The decline in the Monarch population now marks a statistical long-term trend and can no longer be seen as a combination of yearly or seasonal events, experts say.
The announcement followed on the heels of the 20th anniversary of the North American Free Trade Agreement, which saw the United States, Mexico and Canada signing environmental accords to protect migratory species such as the Monarch. At the time, the butterfly was adopted as the symbol of trilateral cooperation.
“Twenty years after the signing of NAFTA, the Monarch migration, the symbol of the three countries’ cooperation, is at serious risk of disappearing,” said Omar Vidal, Omar Vidal, the World Wildlife Fund director in Mexico.
Lincoln Brower, a leading entomologist at Sweet Briar College in Virginia, wrote that “the migration is definitely proving to be an endangered biological phenomenon.”
“The main culprit is now GMO herbicide-resistant corn and soybean crops and herbicides in the USA,” which “leads to the wholesale killing of the monarch’s principal food plant, common milkweed,” Brower wrote in an email.
While Mexico has made headway in reducing logging in the officially protected winter reserve, that alone cannot save the migration, wrote Karen Oberhauser, a professor at the University of Minnesota. She noted that studies indicate that the U.S. Midwest is the main source of the butterflies coming to Mexico. “A large part of their reproductive habitat in that region has been lost due to changes in agricultural practices, mainly the explosive growth in the use of herbicide-tolerant crops.”
While some gardeners and activists in the United States have started a movement to plant small patches of milkweed, the effort is in its infancy. Extreme weather — extreme cold snaps, unusually heavy rains or droughts in all three countries — have also apparently played a role in the decline.
It’s unclear what would happen to the Monarchs if they no longer migrated. The butterflies can apparently survive year-round in warmer climates, but populations in the northern United States and Canada would have to face bitter winters. There is also another small migration route that takes the butterflies to California, but that has also registered declines.
The migration is an inherited trait. No butterfly lives to make the full round-trip, and it is unclear how they remember the route back to the same patch of forest each year, a journey of thousands of miles to a forest reserve that covers 193,000 acres in central Mexico.
Inhabitants of the reserve had already noted a historic change, as early as the Nov. 1-2 Day of the Dead holiday, when the butterflies usually arrive.
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