It rests squarely in the “No shit!” category that monarch butterflies (Danaus plexippus) are an obsession of mine.  From the first time more than 30 years ago when I witnessed voluminous clouds of them roiling across Texas on their way south for winter, I could not help but be fascinated by the spectacle of such a giant movement of insects.  That I live in the path of their largest flyway and not too far north of where the Mexico-bound flyways coalesce adds to my ability to wallow in this superlative natural phenomenon.

In good years, perhaps up to one billion butterflies travel southward into Mexico where they overwinter.  The generation that flies south has never been there before, and these individuals suppress their normally short lives in order to survive for up to six months.  Then in spring they begin their journey northward, mating and laying eggs along the way.  Most of this traveling group will perish before leaving Texas and surrounding states, but their legacy will be the first new generation that will continue the northward march.  Up to four generations are necessary to complete their journey to Canada, at which point the last generation turns south.

Last year I wrote a piece for The Clade discussing the perils faced by monarch butterflies.  I said then that they unfortunately stand in the cross hairs of a twofold threat: habitat loss and climate change.  Illegal logging in their winter territory has destroyed several prime overwintering areas.  In fact, NASA pointed out in its satellite analysis of the monarch reserve that “researchers are greatly concerned that the entire monarch butterfly migration and overwintering phenomenon in eastern North America may collapse in the near future if the Mexican government does not fully enforce the logging ban.”  That enforcement regrettably has yet to happen.

But the other problem, climate change, reared its ugly head with historic drought that gripped Texas for years.  It did not end until winter 2009-2010, meaning butterflies returning in spring 2009 were welcomed into a land of parched, barren earth, few wildflowers upon which to feed, few milkweeds upon which to lay eggs, and a dearth of fresh water to drink.  The expanse of the Lone Star State became one vast minefield bent on destroying what it could of these magnificent creatures.  Yet despite having no choice but to navigate this unwelcoming landscape, the monarchs completed their yearly migration and returned to Mexico in autumn 2009, albeit in smaller numbers than usual due to unfavorable conditions in the US and Canada in summer 2009.  Sadly, the assault on the monarchs was far from over, for their return to the Mexican state of Michoacan would offer them no reprieve from constant attacks.

In any El Niño year the weather patterns over the monarch winter colonies changes, as it does over the rest of the world.  But this year the weather patterns changed into a devastating fight against the monarchs when they are most vulnerable: when the mass of their population is grouped together in small areas.  To wit:

Monarch butterflies, hit hard by strong storms at their winter home in Mexico, have dwindled to their lowest population levels in decades as they begin to return to Texas on their springtime flight back to the United States and Canada.

The monarch loss is estimated at 50 to 60 percent and means that the breeding population flying northward is expected to be the smallest since the Mexican overwintering colonies were discovered in 1975, said Chip Taylor, a professor of entomology and director of Monarch Watch at the University of Kansas.

“I think it is very clear that the butterflies lost more than half of the population,” Taylor said. “I’m hoping it wasn’t as high as 70 or 80 percent. We’ve never seen it this bad before.”

News reports abound explaining of torrential rains and mudslides that devastated the insects.  Serious interest is being paid to the number of individuals now passing through Texas, and a public information campaign has been launched to let people know what they can do to help.

Very much unlike 2009, the generous rain and snow we received from last autumn through winter means the monarchs now traveling through Texas have discovered a world of verdant growth, with wildflowers and milkweeds and fresh water aplenty.  Yet their journey has only just begun.  The availability of milkweeds and flowers in their migration path is the only thing that can help them recover—and it’s believed it will take two or three years for them to fully recover if one assumes conditions remain in their favor.  Which they haven’t been for years.