Monarch Butterfly Population Surges 64% in Mexico Overwintering Season

The monarch butterfly population in Mexico's central mountain forests has surged 64% during the 2025-2026 overwintering season, according to new figures released by Mexico's Ministry of Environment and Natural Resources and the World Wildlife Fund. Monarch colonies now cover 2.93 hectares of oyamel fir forest, up from 1.79 hectares the previous winter.

The increase is welcome news for conservationists who have watched the species' numbers decline dramatically over the past three decades. Improved weather conditions, ongoing reforestation efforts, and reduced illegal logging in the monarch's protected overwintering sites have all contributed to the recovery.

Forest degradation in the monarch reserves also declined significantly, with 6.30 acres degraded between February 2024 and February 2025 — nearly three acres less than the previous year. This reduction in habitat loss is crucial for the butterflies, which cluster on oyamel fir trees in densely packed colonies to survive the winter months.

However, experts caution that the population remains well below historical levels. Scientists estimate that 15 acres of occupied forest is the minimum threshold for the species to be considered above extinction risk. The current population is still down by more than 80-90% since the 1990s peak.

The recovery has been supported by cross-border conservation efforts between Mexico, the United States, and Canada, including habitat restoration along the butterflies' 3,000-mile migration route and the planting of milkweed — the only plant on which monarchs lay their eggs.

Federal protections in the United States, including the species' recent listing under the Endangered Species Act, are expected to provide additional support. Conservationists say the 64% increase demonstrates that sustained, coordinated action can make a meaningful difference for threatened species.