Scientists report 64% increase in migratory monarch butterflies - WWF

After decades of steep decline, the eastern migratory monarch butterfly is showing a rare sign of recovery. New scientific surveys by WWF-Mexico and its partners indicate that the population increased by an estimated 64% during the butterfly’s most recent hibernation season, offering cautious hope for one of the world’s most iconic species.

The monarch population’s increase was measured not by counting individual butterflies, but by tracking how much forest they occupied in central Mexico, where the species overwinters each year. According to the latest assessment, butterflies covered approximately 7.24 acres of forest, up from 4.42 acres the previous winter. Scientists consider this metric a reliable proxy for population size, given the butterflies’ dense clustering during hibernation.

A companion report delivered further encouraging news: forest degradation inside the Monarch Butterfly Biosphere Reserve declined over the same period. Researchers found that roughly 6.3 acres of forest were damaged between early 2024 and early 2025 — a marked improvement from the year before, when losses were significantly higher. Illegal logging remained the principal cause, followed by fires and drought.

The apparent rebound follows years of alarming contraction. Three decades ago, monarchs occupied nearly 45 acres of forest during the winter. Since then, climate extremes, habitat loss across North America and continued pressure on Mexico’s high altitude fir forests have driven a long-term downward trend, punctuated by sharp year to year swings.

Conservation groups caution that the recent gains do not signal a full recovery. Monarchs migrating between Canada, the United States and Mexico face mounting threats, including herbicide and pesticide use that erodes breeding habitat, as well as increasingly volatile weather patterns that disrupt migration and survival at every stage of the journey.

"Despite environmental challenges, today’s announcement shows promising signs of recovery for the migratory eastern monarch butterfly population,” said Maria Jose Villanueva, WWF-Mexico Director General. “These reports indicate conservation measures are going in the right direction. We also need to remain vigilant and not forget that this unique migration continues to face many challenges. WWF will continue to work together with local partners, the Mexican government, and especially with the local communities who are most critical to this success."

Still, scientists and conservationists say the new data shows coordinated action can have measurable impact. Efforts to strengthen forest management in Mexico, restore degraded land, support local communities and reduce harmful pesticide use in the United States are beginning to yield results. The challenge now, experts say, is sustaining those efforts long enough for the monarch’s fragile recovery to take hold.

Read the full report here from WWF and support WWF's global conservation efforts by adopting a Monarch Butterfly here