The population of monarch butterflies wintering in the mountains west of Mexico City has increased significantly, doubling the area they covered in 2024. Experts stated that this recovery happened despite threats such as climate change and habitat destruction. Instead of counting individual butterflies, the annual survey measures the area they occupy as they cluster on tree branches in pine and fir forests. Monarchs from the eastern regions of the United States and Canada migrate to Mexico for the winter. Mexico’s Commission for National Protected Areas (CONANP) reported that the butterflies covered 4.4 acres (1.79 hectares) this year, up from 2.2 acres (0.9 hectares) in 2023, which had marked a sharp 59% decline from the previous year. Improved environmental conditions, such as humidity and temperature, contributed to the population increase.

The migration of monarch butterflies spans thousands of miles, with multiple generations born along the route before reaching Canada. At the end of summer, the final generation travels back to Mexico. Conservation efforts have focused on increasing native plants essential for sustenance and reproduction. However, populations in other regions remain in decline. The Xerces Society for Invertebrate Conservation recorded only 9,119 western monarchs in 2024, marking a 96% decrease from 233,394 the previous year. The primary threats include habitat loss, urban expansion, and the reduction of milkweed plants. Due to these risks, the U.S. Fish and Wildlife Service has proposed granting the species protection under the Endangered Species Act.