MEXICO CITY — The eastern monarch butterfly migration received a hopeful update this spring, with new survey results showing a 64% increase in the amount of Mexican forest occupied by overwintering colonies during the 2025–2026 season.
The annual survey, released by WWF-Mexico and Mexico’s National Commission of Protected Natural Areas, known as CONANP, found that monarch colonies occupied 7.24 acres, or 2.93 hectares, of forest in central Mexico this winter. That is up from 4.42 acres, or 1.79 hectares, the previous season.
The figure does not represent a direct count of individual butterflies. Instead, scientists measure the area of forest covered by dense monarch clusters while the butterflies hibernate in Mexico’s highland oyamel fir forests. Because millions of butterflies can gather in a relatively small area, occupied forest is considered the standard indicator for tracking the eastern migratory population.
The latest survey identified nine monarch colonies this winter: three in Michoacán and six in the State of Mexico. Five colonies were located inside the Monarch Butterfly Biosphere Reserve, while four were found outside the reserve.
The increase is encouraging, particularly after years of steep concern about the future of the migration. Eastern monarchs travel thousands of miles each year from breeding grounds in Canada and the United States to the same mountain forests in central Mexico, where they spend the winter before beginning the return migration north.
Mexico’s role is central. The oyamel forests of Michoacán and the State of Mexico provide the cool, sheltered microclimate monarchs need to survive the winter. Those same forests also support local communities, tourism, biodiversity, and freshwater resources that extend well beyond the butterfly sanctuaries.
A second WWF-Mexico report offered another piece of good news. Forest degradation in the core zone of the Monarch Butterfly Biosphere Reserve declined compared with the previous year. The report found 6.30 acres of forest degradation between February 2024 and February 2025, nearly three acres less than the year before. Most of the loss was attributed to illegal logging, followed by forest fires and drought.
That matters because the monarch’s survival depends on habitat across three countries. In Mexico, the focus is protecting the winter forests. In the United States and Canada, the biggest issues include loss of milkweed and nectar plants, pesticide and herbicide use, extreme weather, and climate change.
The improvement also comes after a second consecutive year of population growth. The 2024–2025 survey showed a rebound from the previous winter, and the 2025–2026 numbers continued that upward movement. Still, scientists warn against reading too much into one or two better seasons.
Monarch numbers naturally fluctuate from year to year. Favorable rainfall, weather conditions, and food availability along the migration route can help the population in a given season. But the long-term trend remains troubling. Three decades ago, monarchs covered nearly 45 acres of forest in Mexico. The current figure, while improved, is still far below historic levels and below what researchers consider necessary for long-term stability.
The western monarch population, which overwinters in California rather than Mexico, remains in even more serious condition. Recent counts there were among the lowest on record, adding to concern over the species as a whole.
In the United States, the monarch butterfly has been proposed for protection under the Endangered Species Act, but a final decision has been delayed. Conservation groups continue to push for stronger protections, while many restoration efforts remain voluntary and community-led.
For now, the latest numbers offer a rare piece of good news. They show that monarchs can respond when conditions improve and habitat is protected. They also show why the work cannot stop.
The 64% increase is not a recovery. It is a reminder that recovery is still possible.
