Monarch butterflies are vanishing. Over the last 20 years, fewer and fewer of them have been making the long journey down to Mexico to survive the winter. By one count, their population has shrunk as much as 90 percent.
The situation has gotten so dire that the federal government may soon step in. Earlier this week, the US Fish & Wildlife Service announced it would conduct a year-long review on whether to list the monarch butterflies as "endangered" or "threatened" under the Endangered Species Act.