WASHINGTON, D.C. — World Wildlife Fund-Mexico’s annual survey of Eastern migratory monarch butterflies overwintering in south-central Mexico shows an estimated occupation of 7.24 acres of forest during the 2025-26 winter. This is a 64 percent increase from the previously reported 4.42 acres but highlights the deficit needed to achieve a stable population.

Dedicated measures, such as the U.S. Fish and Wildlife’s proposal to list the monarch as threatened under the Endangered Species Act, will help sustain this increase and ensure continued population growth.

“This year’s population increase is always welcoming news, but the long-term trend population data shows a continuing decline that we must address if we aim to help monarchs reach a viable, healthy population size,” said Dr. Rebeca Quiñonez-Piñón, senior scientist for the National Wildlife Federation. “Our collective efforts should continue to focus on addressing the threats posed by pesticides, climate change, and habitat loss and the significance of protecting the monarch butterfly under the Endangered Species Act.”