Monarch butterflies are preparing to take their biannual 3,000 mile journey from Canada to their wintering grounds in Mexico, but this is a phenomenon that may soon disappear.

The monarch butterflies' population declined a whopping 90 percent over the past two decades. The Center for Biological Diversity and Center for Food Safety linked up with the Xerces Society and monarch scientist Lincoln Brower to file a legal petition to the U.S. Fish and Wildlife Service seeking Endangered Species Act protection for the declining monarchs.

"Monarchs are in a deadly free fall and the threats they face are now so large in scale that Endangered Species Act protection is needed sooner rather than later, while there is still time to reverse the severe decline in the heart of their range," said Lincoln Brower, preeminent monarch researcher and conservationist.

Researchers believe the monarchs' decline is strongly linked to the planting of genetically engineered crops in the Midwest, which is the birthplace of most monarchs. These crops are made to be resistant to Monsanto's Roundup herbicide, which is deadly to monarch caterpillars' only food, milkweed.

"The widespread decline of monarchs is driven by the massive spraying of herbicides on genetically engineered crops, which has virtually eliminated monarch habitat in cropland that dominates the Midwest landscape," said Bill Freese, a Center for Food Safety science policy analyst. "Doing what is needed to protect monarchs will also benefit pollinators and other valuable insects, and thus  safeguard our food supply."

Researchers also believe climate change could be driving the monarchs' decline because droughts and heat waves are threatening their crucial wintering grounds. In the mid-1990s there were approximately one billion monarch butterflies, this number declined to only 35 million butterflies last winter, which is the lowest number ever recorded.

"We're at risk of losing a symbolic backyard beauty that has been part of the childhood of every generation of Americans," said Tierra Curry, a senior scientist at the Center for Biological Diversity. "The 90 percent drop in the monarch's population is a loss so staggering that in human-population terms it would be like losing every living person in the United States except those in Florida and Ohio."

The Fish and Wildlife Service must now issue a "90-day finding" on whether or not the petition requires further review.