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Groups Want Monarch Butterfly Declared A Threatened Species

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Monarch butterfly | Photo: Eric Farkas/Flickr/Creative Commons License

In a move that would have been nearly incomprehensible 20 years ago, environmental groups are asking the federal government to grant Endangered Species Act protection to a popular butterfly that was once one of North America's most common large insects. In a petition filed Tuesday with the U.S. Fish and Wildlife Service, three conservation organizations and a leading lepidopterist are asking USFWS to declare the monarch butterfly a threatened species.

The petition is prompted by a staggering drop in monarch numbers over the last two decades; current estimates put that drop at 90 percent in the last 20 years. The groups cite a rise in use of the herbicide Roundup as a key factor in the monarchs' decline. Farmers using the herbicide have wiped out much of monarch's supply of milkweed plants across the continent; monarchs require milkweed in order to reproduce successfully.

"Monarchs are in a deadly free fall and the threats they face are now so large in scale that Endangered Species Act protection is needed sooner rather than later, while there is still time to reverse the severe decline in the heart of their range," said petitioner Lincoln Brower, who has been studying monarch butterflies since 1954.

Brower's co-petitioners are the Center for Biological Diversity, the Center for Food Safety, and invertebrate conservation group the Xerces Society.

The monarch, Danaus plexippus plexippus, lays its eggs exclusively on plants in the genus Asclepias, a.k.a. milkweed. The species' striking green, yellow, and black caterpillars emerge from those eggs and begin to eat the plants. Monarchs can't use any other kind of plant as a larval food source, so the species' fate is tied to that of the milkweed.

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With the advent of genetically modified corn and soybeans designed to resist the effects of the broad-spectrum herbicide glyphosate, trade-named Roundup, use of the herbicide has increased dramatically over the last two decades. That increased use of Roundup is also spurred by federal energy policy, as we reported here in February: subsidies to encourage growing corn for ethanol have encouraged a huge increase in acreage devoted to growing corn: about 30,000 square miles more than in 2007.

Milkweed has historically been a common but relatively benign weed in farm fields and in uncultivated land adjacent to those fields. Roundup-resistant crop plants changed that. Farmers can spray their fields with herbicide without damaging their crops. That's bad for the milkweeds, which have no such resistance to the herbicide. And the increase in corn cultivation for ethanol production has turned much former milkweed habitat into corn fields.

As a result, monarch butterflies have declined from an estimated billion in the mid-1990s to about 35 million this past winter. The showy insects face more threats than loss of their larval food plant: reduced numbers make the population more susceptible to damage from storms, predation, and other pesticides.

Now that the petition is filed, USFWS has 90 days to issue a "finding" -- a formal decision whether or not to review the petition further. The soonest the butterfly could win ESA protection is two years from the petition date.

"We need to take immediate action to protect the monarch so that it doesn't become another tragic example of a widespread species being erased because we falsely assumed it was too common to become extinct," said Sarina Jepsen, endangered species director at the Xerces Society. "2014 marks the 100th anniversary of the extinction of the passenger pigeon, which was once so numerous no one would ever have believed it was at risk of extinction. History demonstrates that we cannot afford to be complacent about saving the monarch."

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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