Science & Nature

This Year’s Monarch Butterfly Count Rebounded From 2024 Crash, But Numbers Still Well Below Sustainable Target

The monarch butterfly population has rebounded from a near record low number in 2024, according to the latest annual survey conducted by the World Wildlife Fund-Mexico.

But while the numbers for the 2024-25 hibernation season are nearly double last year’s, the tally still remains well below the target scientists have set for maintaining a sustainable monarch population.

Researchers estimate the size of the monarch population by measuring the area of forest the butterflies occupy at their winter sites in Mexico. This year, the butterflies spanned 4.42 acres, up from 2.22 acres in 2023-24. The recommended threshold for supporting a healthy monarch population is closer to 15 acres. 

(World Wildlife Fund)

“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,” according to World Wildlife Fund.

There were also improved forest protections in the core zone of Mexico’s Monarch Butterfly Biosphere Reserve, where the species overwinters.

Despite these gains, overall habitat loss across the butterflies’ lifecycle — from breeding grounds, to its migratory route, to wintering sites — remains the biggest threat to the monarch’s survival. Severe weather, climate change and pesticide use have also contributed to the species' decline.

Conservation efforts in the Midwest are focused on planting milkweed and nectar-rich flowers to help bulk up the breeding population in advance of their journey south.

The scale of those measures could increase dramatically now that the U.S. Fish and Wildlife Service has proposed the monarch for listing as an endangered species. People have until Wednesday to submit a comment regarding that proposed listing. 

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