"MEXICO CITY -- The number of Monarch butterflies making it to their winter refuge in Mexico dropped 59 percent this year, falling to the lowest level since comparable record-keeping began 20 years ago, scientists reported Wednesday."
"It was the third straight year of declines for the orange-and-black butterflies that migrate from the United States and Canada to spend the winter sheltering in mountaintop fir forests in central Mexico. Six of the last seven years have shown drops, and there are now only one-fifteenth as many butterflies as there were in 1997.
The decline in the Monarch population now marks a statistical long-term trend and can no longer be seen as a combination of yearly or seasonal events, the experts said.
But they differed on the possible causes."