Monarch butterflies may migrate

As many as 200 million Monarch butterflies may migrate to Mexico this year a nearly tenfold increase over 2004.

As many as 200 million Monarch butterflies may migrate to Mexico this year a nearly tenfold increase over 2004, when unfavourable weather, pollution and deforestation caused a drastic decline in the population, environmental officials said on Tuesday.

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Last year, fewer than 23 million butterflies survived long enough to leave habitats in the United States and Canada for sanctuaries in the state of Mexico, which borders Mexico City, and neighbouring Michoacan state. That was at least 75 per cent lower than expected, but should usher in a Monarch resurgence this year, officials said.

After especially cold weather reduced the butterfly population to 28 million during the 2000-2001 migration period, the number of Monarchs swelled to 93 million the following year. No one knows for sure how many butterflies make the annual migration south, but 2005 estimates will be aided by a new counting system that better determines the thousands of butterflies on each acre of territory.

The Monarchs’ annual 3,400-mile journey from the forests of eastern Canada and parts of the US to the central Mexican mountains is an aesthetic and scientific wonder. The butterflies began reaching Mexico last week and usually continue to stream south until early December. The spectacle of millions of orange and black butterflies carpeting fir trees attracts 200,000 visitors a year.