"...Over the past couple of years, the number of monarch butterflies that reach the Mexican sanctuaries has been declining, generating concern among rural communities that rely on spillovers of butterfly tourism activities, as well as entomologists, biologists, ecologists and monarch aficionados around the world. ..."

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The probable causes for the decline in butterflies during the migration and hibernation between 2012 and 2013 are the reduction in milkweed availability in feeding and reproduction sites throughout the United States and Canada, and extreme weather events affecting the reproductive generations in the United States during spring and summer 2012, [a] report said."

Ines Perez reports for ClimateWire March 27, 2013. [2]