Fewer monarch butterflies wintering in Mexico

The HoustonChronicle reports on the decline of Monarch Butterflies expected this year:

The number of monarch butterflies wintering in Mexico has declined by 75 percent this year, and some researchers warned Thursday that conditions in this country as well as in the United States and Canada threaten the survival of one of nature's great wonders.

"We're getting to what we see as a really dangerous situation for the future of the monarch," said Lincoln Brower, a biologist at Sweet Briar College in Virginia and a leading butterfly expert.

Each year, millions of monarchs make a remarkable journey of up to 2,500 miles from Canada and the United States to a remote, mountainous area in the central Mexican state of Michoacan where they spend the winter. The butterflies attract thousands of tourists.

Mexico's Environment Ministry issued a statement this week that blamed the population decline on unseasonably cold weather last spring and summer in North America and on increased use of genetically modified crops and herbicides there. But a report, put out Thursday by Brower and other leading monarch researchers, said the U.S. and Canadian factors merely exacerbated the menace posed by continuing deforestation in the Michoacan mountains.

Jeffrey Glassberg, the president of the North American Butterfly Association, pointed out that insect populations can rise and fall by 50 percent or more from year to year. One bad year does not necessarily make for a species-threatening trend, he said. "Monarchs are not in any threat of extinction," Glassberg said. "With a one-time event like this, without more information, one can only speculate what the cause might be."

The monarchs' migration from the northern United States and Canada each fall and back again in the spring constitutes one of the most dramatic journeys of its kind in nature. Leaving their summer grounds at the end of August, the insects fly as many as 2,500 miles and arrive by early November in Mexico at a five-acre patch of pine-covered mountainside. The monarchs spend the winter clustered by the thousands in pods hanging from tree branches. They head north again in early March. By the time they reach their summer grounds, where they breed and die, some of them will have traveled more than 5,000 miles in all.