Monarch Butterflies Are Out of the Woods

New NASA satellite images show clearly that deforestation is eroding critical habitat for the monarch butterfly, a beloved visitor to North America whose amazing migration takes it to the highlands of central Mexico each winter in masses millions strong. Habitat in Mexico is limited to just 12 forested mountaintops, according to NASA, and millions of butterflies cluster together in these areas. The fact was brought home to North American audiences vividly several years ago when a freak frost killed so many butterflies they piled on the ground chest-deep. But illegal logging in the Monarch Butterfly Biosphere Reserve has been destroying this critical habitat at a startling pace, as the new satellite images show.

Not only may monarchs lose favored spots that they have returned to repeatedly, but if they do choose to overwinter in deforested areas, they are less likely to survive the winter. Some scientists say the entire extraordinary migration of the monarch butterfly is in danger of collapsing. (If you live in the Northeast, where monarch spend the summer, and you want to support migratory birds, butterflies and other wildlife, go to the New Jersey Audubon Society for a dozen must-have plants.

Here's NASA's description of the images:

The white line indicates the boundaries of the reserve’s “Core Zone,” where logging is forbidden according to the Presidential decree that established the reserve in November 2000. This pair of images shows the affected area on March 22, 2004 (top) and February 23, 2008 (below). The degraded area is the site of the Lomas de Aparicio monarch colony. The circles on the image indicate the approximate positions of the colony in different seasons. Colonies typically cover areas of about 200-525-foot diameter areas. The area had been largely intact since at least 1986. Overwintering colonies have been documented there since 1996, but have probably formed there long into the past.

In the 2004 image, the beginnings of the logging operation are apparent in an area to the east of (and partially inside) the core zone. Based upon this pair of images, and a similar image taken in 2006 by the QuickBird satellite, scientists Lincoln Brower, Daniel Slayback, and Isabel Ramirez have determined that approximately 1,110 acres of forest were logged between 2004 and 2008, representing 3.3% of the 33,410-acre core zone of the reserve. The majority of this logging (717 acres) has occurred since March 2006.

Deforestation in Mexican habitat of the monarch butterfly is eroding critical habitat.
NASA Earth Observatory

Imagine this video footage in the absence of trees:

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