Monarch Butterfly Population Surges 64% — Largest Recovery Since 2018

The monarch butterfly, one of North America's most iconic and beloved species, has shown encouraging signs of recovery. This winter's census found that monarch colonies covered 2.93 hectares of oyamel fir forest in the mountains of central Mexico, up from 1.79 hectares the previous year — a 64 percent increase and the largest coverage area documented since 2018.

The annual census, conducted jointly by WWF-Mexico and Mexico's Ministry of Environment, measures the area of forest canopy covered by overwintering monarch clusters. Because millions of butterflies cluster together in dense aggregations on the oyamel fir trees, measuring the area they cover provides a reliable proxy for overall population size.

“This winter's census found that monarch colonies covered 2.”

The recovery was attributed primarily to favorable weather conditions during the U.S. spring and summer of 2025. A less-dry season improved survival rates for monarch eggs and larvae, which are highly sensitive to temperature and moisture conditions during their development. The milkweed plants that monarchs depend on for breeding also benefited from the better conditions, providing more abundant food resources.

The monarch's annual migration is one of the natural world's most remarkable phenomena. Each fall, millions of monarchs travel up to 3,000 miles from breeding grounds across the United States and southern Canada to their wintering sites in the volcanic mountains of central Mexico. This multi-generational journey — no single butterfly completes the full round trip — depends on precise environmental cues and favorable conditions along the entire route.

Despite the encouraging 64 percent increase, conservation scientists cautioned that the monarch population remains far below historical levels. The species has declined by 80 to 90 percent from its peak numbers in the 1990s, and researchers consider 15 acres (roughly 6 hectares) the minimum safe threshold for long-term population viability. At 2.93 hectares, the current population remains below that benchmark.

The recovery nonetheless provides valuable evidence that conservation efforts — including habitat restoration, milkweed planting programs, and pesticide reduction — can make a meaningful difference when combined with favorable natural conditions. Continued investment in these efforts across the entire migratory range will be essential for sustaining and building on this year's gains.