After years of alarming decline, the eastern migratory monarch butterfly has had its best winter in eight years. New survey data from WWF Mexico and partners confirms that the butterflies covered 2.93 hectares of oyamel fir forest in their Mexican wintering grounds during the 2025-2026 season — a 64% increase over last year 1.79 hectares, and the largest area recorded since 2018.
A colony in full roosting mode looks like the trees themselves are alive with orange — millions of wings folded, clustered so tightly that branches bend under their weight. This year, that spectacle returned in force across the mountains of Michoacán and Estado de México.
Why This Winter Matters
The monarch survey, released in March 2026, measures the area of forest where monarch colonies are dense enough to be counted. Scientists point to a combination of factors: reduced illegal logging in the Sierra Chincua and Cerro Pelón sanctuaries, good breeding conditions in North America in 2025, and community conservation programmes where local landholders are paid to protect butterfly colonies.
Still a Long Way to Go
Experts are cautious. The population is still well below the 6 hectares that would give the species a reasonable margin of safety. Climate change continues to threaten both wintering habitat and the milkweed that caterpillars need along the migration route. The journey from Mexico to Canada — up to 4,800 kilometres — is a gauntlet no single winter improvement can fully address.
This is the second consecutive year of increase — the first back-to-back gain since 2020.
Sources: WWF Mexico, Monarch Joint Venture, Journey North, The Guardian (March 20, 2026)
