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Monarch Butterflies Migration Decreases as Herbicide Increases

The number of Monarch butterflies migrating to Mexico dramatically dropped this year to its lowest level since studies first began in 1993, leading experts to announce Wednesday that the insects’ annual migration from the United States and Canada is in danger.

Monarch Butterflies

Image courtesy of Wikipedia

A report released by the World Wildlife Fund, Mexico’s Environment Department and the Natural Projected Areas Commission blamed the displacement of the milkweed the Monarch butterflies 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 safety and shelter.

After noticeable declines in the previous three years, the black-and-orange butterflies now only cover 1.65 acres in the pine and fir forests west of Mexico City, compared to the 2.93 acres last year. At their peak, they covered more than 44.5 acres in 1995.

Because the Monarch butterflies clump together by the thousands in trees, they are counted by the area they cover per the Chronicle Herald.

The decline in the Monarch population now marks a statistical long-term trend and will no longer be seen as a combination of seasonal or yearly events, experts say.

The announcement coincidentally comes 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 the co-operation.

“Twenty years after the signing of NAFTA, the Monarch migration, the symbol of the three countries’ co-operation, is at serious risk of disappearing,” said Omar Vidal, Omar Vidal, the World Wildlife Fund director in Mexico.

“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,” leading entomologist at Sweet Briar College in Virginia wrote in an e-mail.

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