Wildlife conservationists sounded the alarm Wednesday as an annual count of monarch butterflies revealed a sharp decline in the number of the iconic insects hibernating in Mexican forests, stoking renewed fears of their extinction.

The annual survey—led by Mexico’s National Commission of Natural Protected Areas and the Mexican branch of the World Wildlife Fund for Nature (WWF)—showed a 22% drop in the hibernating monarch population amid accelerating habitat loss driven primarily by deforestation.

“Despite heroic efforts to save monarchs by planting milkweed, we could still lose these extraordinary butterflies by not taking bolder action,” Tierra Curry, a senior scientist at the Center for Biological Diversity (CBD), said in a statement.

“Monarchs were once incredibly common,” she added. “Now they’re the face of the extinction crisis as U.S. populations crash amid habitat loss and the climate meltdown.”

Renowned for its epic annual migrations from the northern U.S. and southern Canada to Florida, California, and Mexico, monarchs have suffered a precipitous plunge in population in North America this century.