Eastern monarch butterfly population nearly doubles in 2025

In encouraging news, the eastern monarch butterfly population nearly doubled in 2025, according to a new report announced in Mexico. The population wintering in central Mexico's forests occupied 4.42 acres, up from 2.22 acres during the previous winter. While monarchs occupied nearly twice as much forest habitat as last year, populations remain far below the long-term average.

The survey, Forest Area Occupied by Monarch Butterflies Colonies in Mexico During the 2024-2025 Hibernation Season is conducted annually by WWF-Mexico and Mexico's National Commission of Protected Natural Areas in collaboration with local communities, and it serves as an important indicator of the butterfly's overall population health. 

“We recognize the key role of local communities, as well as the support of the government of Mexico in conserving the forest and providing this iconic species with the opportunity to thrive,” said Jorge Rickards, director general of WWF Mexico. "It’s now time to turn this year’s increase into a lasting trend with an all-hands approach where governments, landowners, conservationists, and citizens continue to safeguard critical habitats along the monarch’s North American migratory route.”

Scientists attribute much of this year’s population growth to better weather conditions in 2024—with less severe drought than in previous years—along the butterflies' migration route from the United States and Canada to Mexico.

Forest protections are also improving

A second report shows that forest degradation in the core zone of the Monarch Butterfly Biosphere Reserve where the species overwinters decreased by 10%. Between April 2023 and February 2024, 9.14 acres of forest were damaged, down from 10.13 acres reported the previous year, according to the Forest Degradation at the Core Zone of the Monarch Butterfly Biosphere Reserve (2023-2024).

The main causes of forest degradation were illegal logging (6.17 acres); natural causes, primarily drought (2.47 acres); and the removal of trees to prevent disease spread (0.45 acres).

Challenges remain in protecting monarchs and forests

Monarchs still face several threats. For example, climatic variations in the monarch’s breeding areas in Canada and the United States can impact the abundance of milkweed, the only plant in which the butterflies lay their eggs, and from which monarch caterpillars feed. Land-use changes in the United States, combined with the widespread use of herbicides and insecticides, have also contributed to the loss of milkweed and other nectar plants adult monarchs need to feed from. And while high levels of illegal logging in the monarch butterfly reserve have been halted, forest degradation in the overwintering sites in Mexico could be a threat if left unchecked.

Why conservation of the Monarch Butterfly Biosphere Reserve matters

Monarchs need large, healthy forests to protect them from winds, rain, and low temperatures common at night in these forests. The health of these forests also supports local communities; improves water quality in the Cutzamala system for almost 6 million people in Mexico City and surrounding areas; and hosts incredible biodiversity, including 132 bird species, 56 mammal species, 432 plant species, and 211 species of fungi.

As pollinators, monarch butterflies contribute to healthy ecosystems across North America. With 80% of agricultural food production depending on pollinators like monarchs, protecting them helps us all.

The amazing monarch migration

Every year, monarch butterflies make an extraordinary journey: at summer's end, they migrate from southern Canada and the northern United States to mountain forests in Mexico, with some traveling nearly 3,000 miles. After winter, these same butterflies fly an additional 600 miles north to the United States. There they lay eggs on milkweed plants, completing their unique eight-month life cycle. The next three to five generations, each living only three to five weeks, continue the migration northward. Eventually, they reach breeding sites in the northern United States and southern Canada, completing the annual migration cycle.

Learn more about WWF's work protecting pollinators. 

Learn more about monarch butterflies.