CERRO PELON, Mexico — High on a remote mountaintop, Alfredo Cruz Colin gazed at a panorama of giant pines and firs where millions of orange and black monarch butterflies spend the winter after flying up to 2,000 miles from Canada and the United States. He saw two things: one of North America’s most spectacular natural wonders and trees that could be sawed down and sold for $300 each.
“We can contemplate the butterflies,” said Cruz, a lawyer. “Or we can send our children to school and feed our families” with the cash from the cut trees. “It’s a tough choice.”
The winter migration of monarch butterflies to Mexico, a stunning sight that draws vast numbers of tourists to mountain forests 100 miles west of Mexico City, has been devastated this year. One of the chief causes is logging that destroys butterfly sanctuaries, according to Mexican and U.S. environmentalists.
The butterfly population this winter is the lowest since researchers began detailed surveys 12 years ago and perhaps the smallest since the 1970s, when international scientists first discovered the colonies in central Mexico, according to Lincoln P. Brower, a biology professor at Sweet Briar College in central Virginia and an authority on monarch butterflies. He estimated that the population was at least 75 percent smaller than last year’s.
In the last two years the butterflies carpeted an area spanning more than 20 acres, but this winter they cover a little more than five acres, said Ernesto Enkerlin, chief of protected areas for the Environmental Ministry. “We are not happy about having fewer monarch butterflies,” he said.
The reason for the dramatic drop appears to be a combination of particularly cold, stormy weather in North America in recent years, herbicide use in the United States and Canada that is killing milkweed plants where butterflies lay their eggs, and persistent illegal logging in Mexico, according to a report issued last week by a panel of monarch researchers chaired by Brower.
Experts and officials agree that all three factors have contributed to the decline in the butterfly population, but there are differing views on whether the greater blame lies with nature or man. Brower said that without further study, it was impossible to determine what portion of the damage was caused by each factor.
But it is clear that the northeast face of this mountain has “been stripped of forest and burned,” completely destroying long-established butterfly sanctuaries and leaving only one small butterfly area this year, said Brower, who has visited the site almost every year since the mid-1970s.
Conservationists are also concerned about threats from herbicides, which they say are killing thousands of acres of wild milkweed plants in the midwestern United States and Canada. While genetically engineered crops such as soy beans and corn are resistant to the chemicals, the weed-killers are causing massive destruction of butterfly eggs on milkweed leaves, they said.
“Why should we care?” said Brower. “For the same reasons we should care about the Mona Lisa or the beauty of Mozart’s music.”
On this chilly mountaintop, reachable by a long, steep horseback ride up to 10,000 feet above sea level, butterfly colonies hang like enormous orange-and-black beards of Spanish moss. As they stirred to life this past weekend, warmed by the afternoon sun, and took flight by the thousands, Elidio Renya Corona, a park ranger, lamented that the size of the colony had shrunk this year and that loggers were “wiping out” the butterflies’ winter home.
Officials at U.S. and international conservation organizations, which have donated millions of dollars to protect the migrating butterfly, said they were also alarmed at the shrinking population. They noted that in Chincoteague, Va., and Cape May, N.J., two important stops along the monarch route to Mexico, researchers also reported a record low number of migrating butterflies as they passed through last fall.
Scientists agree that the monarch has a great capacity to recover from dramatic die offs. In the winter of 2001-2002, as many as 80 percent of the butterflies in Mexico perished in an unusual winter storm, and the following year their numbers rose again. But scientists said they were more disturbed by the steady deterioration of the butterflies’ North American habitat.
“All of us firmly believe that the butterfly is capable of rebounding, but there is a limit,” Brower said. “How many bales of hay can you put on a camel’s back before the last straw breaks it?”
The butterflies begin arriving on this mountaintop each November, resting on the native oyamel fir trees as they do in more than a dozen sanctuaries in central Mexico, most of them in the state of Michoacan
Enkerlin said he believed the low count was mainly due to the small numbers that arrived from breeding grounds in the United States and Canada. He said the Mexican government had recently sent in soldiers and other federal law enforcement officials, and installed surveillance cameras, to seal off core areas of the reserve from illegal logging.
But a press release last week from the Environmental Ministry played down logging as a cause for the small butterfly population this year, prompting angry responses from environmentalists.
“It is a lie” to say illegal logging is not a huge problem, said Homero Aridjis, an environmentalist who grew up near the sanctuaries. He said the forests were under “systematic, criminal” attack by loggers. He also said that Mexico, Canada and the United States were not doing enough to protect this prize of nature.
Under a 1986 presidential decree, the sanctuaries were declared a national park where logging was forbidden. But officials and local residents said thousands of people continue to cut down trees inside the protected area, which covers 135,000 acres. Some of the logging is organized, with groups armed with guns and chain saws filling trucks with freshly cut trees. Other culprits are individuals with axes, cutting a tree to get cash for food or clothes.
Many local residents, nearly all poor farmers, said it was unfair for the government to forbid them from cutting down trees in the forests as their fathers and grandfathers had. “They care more about insects than people,” said Hector Ramirez, who lives on Cerro Pelon and guides tourists into the sanctuary. “The forest is the only thing we have.”
Omar Vidal, director of the World Wildlife Fund office in Mexico, said that between 2000 and 2004, $1 million in private funds from the United States and government funds from Mexico had been paid to local residents as an incentive not to cut trees and for their help in conserving the forests.
But Cruz said the money wasn’t enough to stop the logging. Residents interviewed here said that two years ago, each family received about $150 to $200, but that last year the amount dropped considerably. Cruz said a typical family needed about $800 a year to survive.
Early Saturday morning, before a stream of tourists reached the top of Cerro Pelon on horseback to marvel at the spectacle of the butterflies, more ominous noises echoed through the pine forest: the rhythmic thunk of an ax and the roar of a chainsaw.