Monarch butterfly one knows when millions of monarch butterflies began crisscrossing, North America spending their winters clustered on the same hillsides in central Mexico, a blaze of orange wings in the green forest.
But over the centuries, they were mythologized by generations of humans. Locals believed they carried the souls of their ancestors. Scientists saw the Migration as the proof of insect evolution – a brittle organism that could fly 6,000 miles a year to avoid severe weather.
Now, the monarch has morphed into a different kind of symbol. One of the world’s oldest, most resilient species could be destroyed – and soon – by Climate Change. The butterflies are among the world’s experts in climate adaptation. They spend their summers in the northern United States and Canada; they breed in the southern United States during the fall and spring; and most spend their winters in central Mexico, in a few giant clusters.
Their life cycles are driven by a search for optimal conditions: temperatures ideally between 12C and 22C when they migrate, some rain during their winters, and plenty of milkweed when they mate. The criteria are narrow – and dependent on relatively consistent weather patterns.
That consistency no longer exists. Now summer temperatures in the midwest are soaring. The milkweed in Texas is drying up. Winter storms, once rare, are snaking through central Mexico regularly as the air warms over the Pacific Ocean and blows across the region.
“The question we’re asking is: can one of the world’s most adaptive insects adapt to climate change?” says Karen Oberhauser, who studies the species at the University of Wisconsin. “We are changing the conditions and just waiting to see.”
To specialize in monarch butterflies in 2019 is to wonder constantly if your work is about to go extinct. While almost all species could eventually be consumed by a changing climate and habitat loss, few are as likely to vanish as abruptly as the monarch.
Between 1990 and 2015, the US Fish and Wildlife Service says, a billion butterflies vanished. Because more than 95 percent of the population migrates en masse to a few patches of Mexican forest, each smaller than half a football field, a single storm or heat stroke could effectively kill off the population. (A smaller percentage of the butterflies winter in southern California or Florida, where they face their own challenges.)
That nearly happened in 2002, when a winter storm killed about 75 percent of monarchs. And again in 2012, when a heatwave in the midwest killed tens of thousands. “At every stage in their migration, they are threatened by climate change,” says Eduardo Rendón, the monarch butterfly coordinator for the World Wildlife Fund in Mexico.