Monarch Count Shows Another Sharp Decline

Annual State Tally Reveals Second Lowest Overwintering Population Ever Recorded

A lone monarch butterfly at an overwintering site in Pacific Grove, California in 2022. | Credit: Isis Howard, Xerces Society

Clusters of vibrant orange-and-black wings are disappearing across California. Despite recent recovery efforts, the reign of the monarch butterflies continues to decline.

On Thursday, the Xerces Society released the results of its 28th annual Western Monarch Count, reporting the second lowest overwintering population ever recorded since tracking began in 1997.

This year, the peak population was just 9,119 monarchs, slightly above the all-time low of 2,000 in 2020.

For comparison, almost 233,000 total butterflies were counted in 2023-2024, reflecting the past three years of rebound before this latest drop. Rewind to the 1980s, and there were millions of the insects all over the state.

This year’s count was looking sad from the get-go. Usually, during peak winter activity, the Goleta Monarch Butterfly Grove at Ellwood Mesa is blanketed by monarchs. They hang in bunches from trees and dominate the airspace.

At times this winter, however, only three individual monarchs were observed across multiple sites in the park, the Xerces Society reported.

At the Dangermond Preserve in Santa Ynez, the picture isn’t much prettier. It was a top host last year, accommodating 33,200 monarchs. Only 198 showed up this year.

So, why the sharp decline? The main culprit, it seems, is climate change.

Total monarchs reported and number of overwintering sites monitored for the Western Monarch Count from 1997 to 2024. | Credit: Xerces Society

“The population’s size is extremely concerning,” said Emma Pelton, an endangered species biologist with the Xerces Society for Invertebrate Conservation. “We know small populations are especially vulnerable to environmental fluctuations, and we think that’s what happened this year.”

Record summer temperatures and drought were likely contributors to the massive drop-off scientists saw in breeding generations, she said.

After breeding up north during the spring and summer, the butterflies migrate to California in search of warmer temperatures. But dangers lie throughout their migratory range, Pelton added. Those include pesticides, habitat loss (such as fewer milkweed on which to lay their eggs), and increasingly severe weather exacerbated by climate change.

January’s fires in Los Angeles County are also to blame. The fires burned tree groves where monarchs gather, including a site in Lower Topanga Canyon.

Because of these significant declines, in December, the U.S. Fish and Wildlife Service proposed to list the monarch butterfly as a threatened species under the U.S. Endangered Species Act. When it is finalized, the label is expected to provide vital support for the species, including greater protection for overwintering habitat in California. A public comment period on the listing is open until March 12, and the Xerces Society is asking individuals to sign on to support the listing.

Right now, volunteers can sign up to help restore habitat for the monarchs by planting trees at Ellwood Mesa. After a short break for the holidays, UC Santa Barbara’s Cheadle Center, the City of Goleta, and Your Children’s Trees are resuming volunteer work Saturday mornings through February 22.