Liza Gross in The New York Times:
Dara Satterfield hadn’t planned to conduct experiments at the Texas State Fair, but that is where her study subjects showed up last month. She was still in Georgia when they arrived, so she hurriedly packed her car, then drove all night. As she pulled into the fairgrounds in Dallas the next morning, they were feasting on nectar-filled blossoms of frostweed alongside the Wild West Pet Palooza. The hungry travelers, like most monarch butterflies that migrate from breeding grounds in the northern United States and southern Canada, had stopped in Texas to consume enough calories to power the last leg of their flight to the oyamel fir forests of central Mexico and survive five months overwintering there. So many monarchs blanketed the frostweed that Ms. Satterfield, a 27-year-old doctoral student at the Odum School of Ecology at the University of Georgia, allowed herself to hope that one of the world’s most celebrated migrations could be revived.
Less than 20 years ago, a billion butterflies from east of the Rocky Mountains reached the oyamel firs, and more than a million western monarchs migrated to the California coast to winter among its firs and eucalypts. Since then, the numbers have dropped by more than 90 percent, hitting a record low in Mexico last year after a three-year tailspin. Preliminary counts of migrants this fall are encouraging. “But we’re definitely not out of the woods,” said Ms. Satterfield, who studies human effects on migratory behavior. “One good year doesn’t mean we’ve recovered the migration.” To make matters worse, she and her graduate adviser, Sonia Altizer, a disease ecologist at Georgia, fear that well-meaning efforts by butterfly lovers may be contributing to the monarch’s plight.