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Winter monarch population is lowest ever; annual migration at risk

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A University of Minnesota researcher is one of several experts making an urgent plea for North American leaders to take immediate action to save Minnesota's state insect.

The results from an annual survey released Wednesday show that the wintering monarch butterfly population in central Mexico is at its lowest level since studies began about 20 years ago, the Associated Press reports.

U of M entomologist Karen Oberhauser, a longtime researcher of monarchs in North America, is one of several experts that say the annual butterfly migration from the U.S. and Canada to Mexico is in danger of disappearing.

Oberhauser says the primary culprit is the extermination of milkweed – the butterfly's principal food plant – by genetically modified crops in the Midwest.

"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," Oberhauser told the Associated Press.

The Star Tribune reports the crops allow farmers to use herbicides later in the growth cycle, which has led to major reductions in native milkweed and nectar plants that the butterflies rely on during breeding.

In Mexico, illegal logging has caused a dramatic reduction the monarch's habitat, which the country has made an effort to cracked down on.

The gathering of the butterflies in Mexico has been a major tourist attraction in Mexico. Some activists in the both Mexico and the U.S. have started a movement by planting small plots of milkweed to maintain the monarch population, but the effort is in its infancy, according the Associated Press.

The Star Tribune says scientists are calling on public officials in Canada, U.S. and Mexico to develop a conservation plan when they meet next month at North American Leaders’ Summit.

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