The overlay, taken from Journey North shows Monarch Butterfly wintering zones near Mexico City. Zoom in on any of the black squares that designate Monarch colonies and fade overlay to see habitat destruction.


From: Monarch Watch

"Eastern Monarchs migrate only to the Transvolcanic Mountains in Mexico, where there are only eleven to fourteen known sites each year. Each site is a few hectares in size and contains millions of Monarch butterflies. This combination - a high concentration of individuals in a only few small sites - makes the possibility of habitat destruction in Mexico very serious. This is particularly true because the oyamel trees, on which the Monarchs cluster, are valuable lumber sources that many local people - the ejidatarios who own the land - depend upon for income. Logging not only removes roost trees, but also opens up the forest canopy. These gaps are like holes in your winter coat, as far as the Monarchs are concerned. They let in snow and rain, and the roosting Monarchs are more vulnerable to freezing. In December 1995, scientists estimate that 5 to7 million Monarchs died after a snowstorm hit the overwintering sites. A snowstorm in 1992 killed a similar number. Five sites are protected from logging by a government decree, but lumber is still removed from buffer zones around these sites. Although it's important, logging isn't the only cause of habitat destruction near the overwintering roosts. As local human populations grow near these sites, ejidatarios also use the lumber for building materials and the cleared land for growing food and grazing cattle. If the roost sites are destroyed through these activities, Monarch populations are likely to drop precipitously."