While international efforts are under way to help keep dwindling populations of monarch butterflies from disappearing, scientists are raising concerns about how severe weather and a loss of forest habitat at their wintering grounds in Mexico are affecting them.Every year, monarchs embark on an epic multigenerational migration that takes them thousands of miles from Canada and the U.S. in search of sites in California and in Mexico. The fir trees in the southern regions offer the shelter and warmth they need to survive the winter.Unfortunately, these vital forests in Mexico have been threatened by illegal logging, and now storms have destroyed hundreds of acres of habitat, while severe weather is believed to have killed an estimated 6.2 million of these iconic butterflies.