Monarch crash has roots in U.S. suburbs, farms — not just Mexican damp

Greg Harman
gharman@sacurrent.com

The spring monarch migration has been a bust. Only a lucky few have caught sight of more than a couple of the iconic insects currently on their northward jaunt through Texas.

Mainstream news reports have cited key culprits of the population collapse of this most recognizable of the flitter-bys. Soggy weather and illegal logging have both indisputably blitzed the butterflies at their Mexican over-wintering grounds. Less widely reported is the on-going loss of habitat in the United States, as well as our widespread use of toxic herbicides, pesticides, and use of genetically modified corn, many varieties of which are known to be damaging to the insects.

“Their breeding ground is being ‘cleansed,’ as it were, of milkweed. People are using Roundup Ready crops, herbicide-ready crops,” said Mike Quinn, a former Texas Parks & Wildlife entomologist and current president of the Austin Butterfly Forum.

Monarch Watch estimates current agricultural practices — including the war on primary food source, milkweed — have eliminated more than 80 million acres of monarch habitat in recent years.

When the butterflies reach their breeding ground around the Great Lakes region, they’ll be met with sprawling stands of soy and corn crops — herbicide-tolerant crops that have led to an increase in the amount of toxic spraying that has such a negative impact on monarchs.

And some of those Bt-corn varieties aren’t helping, either.

Researchers first began to spotlight the potential risk a decade ago. John Losey, associate professor of entomology at Cornell University, was one of the first to publish findings that showed that monarch larvae fed milkweed leaves dusted with Bt-corn pollen ate less, developed more slowly, and died more frequently than those fed milkweed untainted by the transgenic pollen.

More recent research suggests that fewer than one percent of monarchs are threatened by exposure to Bt-corn pollen. While the total impact may sound small, Losey said it should be considered along with all the other environmental threats impacting monarch populations across the Americas. “People say, ‘Well, there’s these other threats that are large,’ and they are, but the more the populations get squeezed by these other things, that just sort of magnifies whatever mortality could be happening from the Bt corn,” he told the Current.

That’s not to downplay last winter’s soggy weather or its impact on the already vulnerable population. In 2009, the species limped into central Mexico at its lowest numbers since researchers began doing population counts in the 1970s.

Previous crashes in 2002 and 2004 occurred when the populations were above average, Quinn said. “This year the population was at an all time low and then there was the crash that halved that low number. Another, a back-to-back crash would be particularly devastating.”

And while Mexico’s butterfly reserves and Midwest breeding grounds may feel far from us in South Texas, there’s a lot local residents can do to help. Texas is a “springboard” for the northward migration, the site of the monarchs’ first rush of egg laying. “So the conditions here in Texas play a big role in the success of future monarch generations going north,” said Quinn, who also maintains the Texas Monarch Watch website.

Quinn will be joining a list of presenters at Cibolo Nature Center next Friday and Saturday to train local citizen scientists to lend a hand.

From the CNC website:

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