The number of monarch butterflies spending the winter in the mountains west of Mexico City has significantly increased, doubling in size in 2024. Experts noted this improvement despite ongoing challenges like climate change and the destruction of their natural habitats. Researchers do not count individual butterflies; instead, they measure the space the butterflies occupy as they gather in large groups on tree branches within pine and fir forests. Monarchs from eastern regions of the U.S. and Canada make this migration to Mexico each winter. According to Mexico’s Commission for National Protected Areas (CONANP), butterflies covered an area of 4.4 acres (1.79 hectares) this year, compared to just 2.2 acres (0.9 hectares) in 2023, which had seen a sharp 59% decline. Good weather conditions, including ideal humidity and temperatures, have helped this population rebound. Monarch butterflies migrate thousands of miles, producing several generations along their journey to Canada. The last generation then migrates back to Mexico. Conservationists are working to restore native plants crucial for butterfly feeding and reproduction. Despite this success, monarch populations in other areas, particularly the western U.S., continue to decline rapidly.