Hundreds of millions of Monarchs fly from the US and Canada every October, borne by cold fronts and thermal winds, to cluster on fir trees in the mountains of the Mexican state of Michoacan. So numerous are they, overlapping on tree trunks and the ground, that they turn the forest into a landscape of solid orange and black.
At least, they did. Two years ago, the hibernating butterflies covered an area of 42 acres, with up to 50 million on each acre. This year environmentalists found them covering only 13.5 acres, though still alighting hundreds at a time upon the heads and bodies of visitors. When disturbed, they can virtually block out the sky.
"In terms of numbers, there are up to 80 per cent fewer Monarchs this year than last," said Homero Aridjis, leader of the Mexican ecological movement known as the Group of 100. "The oyamel fir forest has been devastated. The loggers are continuing to chop, despite the area's protected status. Even some of the sanctuary guardians employed by the government are involved in the wood trade, selling it to brickmakers who use it to fuel their ovens.
"We found some trees felled with the butterflies still clinging to them, many crushed to death. The loggers are selling sacks of wood to brickmakers for 15 pesos [pounds 1] a load, a tragedy when you think that it takes 60 years for an oyamel [similar to a mulberry] to grow fully. They're not cutting only the old trees, they're cutting the young ones. There are about 15 families cutting up to 30 trees a day in the area declared a sanctuary by the government in 1986."
Mr Aridjis, who has received death threats in the past, has called on Mexico, the US and Canada to act to save the Monarchs "before the loggers do away with the entire forest".
Another problem for the Monarch (Danaus Plexippus) is the influx of tourists. "There are thousands of visitors every weekend. It is like a Mexico City fleamarket, with more than 200 trinket stalls and fast food stands," said Mr Aridjis. "There are no facilities so visitors go to the bathroom in the forest, littering the ground with used toilet paper."
So remote were the Michoacan mountain forests that it was only in 1976 that a hiker happened upon the secret of the Monarchs' previously unknown hideaway. They apparently fly up to a mile high down through the US and across the Gulf of Mexico. In March they head north again, mate in mid- air - the male carrying the female upside-down - and mostly die en route. Their caterpillar offspring, after going through a larval stage of about a week, instinctively fly north towards Canada - and the cycle begins anew. But for how much longer?Reuse content