WASHINGTON— The annual count of migratory monarchs who spend the winter in Mexico was released today and shows that the revered orange-and-black butterflies remain vulnerable to extinction. This year's count of 4.42 acres of occupied habitat nearly doubled since last year but remains perilously low. 

"While it's wonderful news that the monarch population increased this year, their numbers are still down by 80% overall and remain just one-third the size needed to avoid migratory collapse," said Tierra Curry, a senior scientist at the Center for Biological Diversity. "Monarchs still need big help if we're going to save these iconic butterflies from the double threat of climate change and pesticides."

In one of the longest migrations of any insect, at the end of summer eastern monarchs fly from the northern United States and southern Canada to overwinter together in high-elevation fir forests in Mexico. The population size is determined by measuring the area of trees turned vivid orange by the clusters of butterflies. Scientists estimate that 15 acres of occupied forest is the minimum threshold for the migrating pollinators to be above extinction risk in North America.

In December 2024 the U.S. Fish and Wildlife Service proposed to protect monarch butterflies as threatened under the Endangered Species Act in response to a decade of advocacy by conservation groups. In 2014 the Center for Biological Diversity, Center for Food Safety, Xerces Society for Invertebrate Conservation and renowned monarch biologist Lincoln Brower petitioned the Service seeking protection for the butterflies and their habitat under the Endangered Species Act. The listing should become final in December 2025.

"The Fish and Wildlife Service must finalize the listing of monarchs and in so doing protect them from its threats, including and especially pesticides, which have been a major driver of their rapid decline," said George Kimbrell, legal director at the Center for Food Safety. ""The public comment period is open now: urge the Fish and Wildlife Service to protect monarchs not the pesticide industry's profits."

Migratory monarchs face tremendous threats. Their initial decline was driven by widespread loss of milkweed, the caterpillar's sole food source, due to increased use of the herbicide glyphosate on fields of corn and soybeans genetically engineered to resist it. Volatile herbicides sprayed on newer herbicide-resistant crops drift rampantly to reduce floral resources required by adult butterflies. All stages of monarchs are harmed by neonic insecticides used in crop seed coatings and on ornamental plants.

Climate change is degrading the forests where monarchs winter, and erratic weather events are interfering with migration. Grasslands and other green spaces that provide wildflowers for nectaring adults continue to be lost. Millions of monarchs are killed by vehicles every year as they migrate across the continent. In their winter habitat in Mexico, forests and streams are being lost at record rates to grow avocados for unsustainable U.S. avocado demand.

Most monarch butterflies west of the Rocky Mountains overwinter on the central coast of California. The much smaller western migratory population is down more than 95% since the 1980s and numbered less than 10,000 butterflies this winter.

The annual count of winter butterflies is conducted by the World Wildlife Fund-Telmex Telcel Foundation Alliance and the National Commission of Protected Natural Areas in Mexico.