"Not all scientists agree with the findings, which seem likely to fuel an ongoing debate about the threats the butterflies face."
"Every autumn, swarms of migrating monarchs descend on the mountains of central Mexico. It is the final stop on a journey of thousands of miles, as the butterflies travel from their North American breeding grounds to their winter colonies, where they blanket fir trees. Visitors who time their trips correctly might find the air so thick with monarchs that they can hear the butterflies’ wings beating.
“That’s bucket-list stuff,” said Andrew Davis, an ecologist at the University of Georgia, Athens. “Imagine being surrounded by gazillions of butterflies. It’s a magical experience.”
It is also one that may not last. In recent decades, the number of monarchs spending the winter in Mexico and overwintering sites in Southern California has plummeted, prompting concerns that the species might be at serious risk of disappearing."
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