Deadly Winter Stills Butterflies’ Wings in Mexico

A trek through the 9,000-foot-high pine forests of the El Rosario sanctuary normally leads to a breathtaking spectacle this time of year: As the winter sun hits the boughs of the trees in midmorning, millions of monarch butterflies begin to quiver and shimmer, and then take flight.

This year, the butterflies are visible, but they are still. Killed in mid-January by a brutal freeze, they are piled inches deep along both sides of the path.

The days are still so cold that even the surviving monarchs remain motionless, bunched together for warmth in living clumps that dangle from the branches of the towering, rod-straight oyamel trees.

In past years, visitors could watch the sky glitter with the awakening black-and-orange monarchs. They could stand transfixed on the steep path as thousands of butterflies swarmed around them, some alighting on sweaters and hats as the insects raced down into the nearby valley to feed on milkweed plants.

This is one of nature’s magical pageants, more remarkable because these butterflies migrate all the way from Canada each autumn and somehow always find their way back to the same dozen or so mountaintops in the states of Michoacan and Mexico, about a three-hour drive west of Mexico City. They head north again in March, some inner compass guiding their journey.

This year, rotting butterflies give off a faint sickly sweet smell like the innards of a carved pumpkin. Groups of children look for small joy in seeing a few living butterflies resting on a tree stump.

Scientists reported this week that about 80% of the population at El Rosario and 74% at the nearby Sierra Chincua sanctuary--or as many as 250 million butterflies--probably perished in the freeze. Veteran butterfly scientist Lincoln P. Brower of Sweet Briar College in Virginia, who led the study for World Wildlife Fund-Mexico, said he found piles a foot deep in places. He called it by far the worst die-off he had seen in 25 years of studying the monarch.

It would be easier to dismiss this phenomenon as just a profound display of the force of nature if it weren’t for the man-made threats that have made the butterflies’ sojourn constantly riskier. The lands around El Rosario and Chincua have been ravaged by deforestation in recent decades, much of it through illegal logging for commercial lumber.

Government efforts to reduce the cutting, especially an innovative program introduced in 2000 to compensate villagers for not logging, have had some success. But many believe that the gradual reduction of havens for the butterflies contributed to their fate.

The die-off is more disconcerting because it is the second in two years. Last year, some activists worried that pesticide poisoning caused a rash of butterfly deaths in other reserves, but experts determined that a freeze was the culprit.

This year, a heavy snowfall came first, which the butterflies can survive. But two days of freezing rain followed, soaking the butterflies and dragging them to the ground. Scientists say the monarch population is vulnerable but will rebound.

The people of the old mining town of Angangueo and surrounding farming villages have seen their three-month tourist season decimated by the disaster, as word has spread and visitors have opted to stay home.

The sanctuaries have provided work for hundreds of local residents, and people here had begun to recognize that the butterflies and their habitat were a resource that could be worth more than sawed wood.

Laborers at El Rosario had just finished building a handsome trail of sturdy, ochre-colored concrete stairs up the hillside, making the climb easier for children and older people and reducing the dust clouds and slippery mud of years past. Other villagers have set up stalls selling butterfly magnets and pencils and T-shirts. This week the stalls were mostly closed, and dozens of would-be guides stood idle at the reserve’s gates.

One recent weekday morning, only a handful of stalwart tourists made the journey up from the town. One driver, Enrique, said his transport service, using an ancient Chevrolet Suburban, had seen a big drop in business compared with last year.

He said he will cross the border illegally in March, heading for Tennessee to work in a Chinese restaurant. He is one of tens of thousands people in Michoacan who migrate like the butterflies each year, in search of economic opportunities that the monarchs cannot seem to provide at home.

Homero Aridjis, a Mexican writer who was born in Michoacan and who has fought to protect the reserves since the 1980s, said “the scientists and the government say this [die-off] is a natural phenomenon. Yes, but it is aggravated by deforestation. They should declare a moratorium on all logging in the sanctuaries. . . . The most depressing spectacle on those highways is to see trucks full of cut tree trunks coming down from the mountains all day long.”

Aridjis, who is lecturing this semester at UC Irvine, added: “In a country where the environment is so damaged and so polluted, the migration of the monarchs is the liberation of the spirit. It is a poetic journey, it is a journey of the imagination. But there always has been conflict between destruction and protection, between human beings and the butterflies. It has been very frustrating.”