Butterfly Crisis: U.S. and Central Coast Populations Plummet

SANTA BARBARA COUNTY, Calif. – Butterfly populations across the United States are declining, a trend reflected in the Western monarch butterfly population along the California Coast.

A study published in Science found that the total abundance of butterflies declined by 22% from 2000 to 2020. For context, for every five butterflies seen 20 years ago, only four remain, according to the Xerces Society for Invertebrate Conservation. The study also found that 107 species declined by more than 50%, while 22 species saw declines of more than 90%.

“Our study found that the total number of butterflies declined by 1.3% per year,” said Collin Edwards, the study’s lead author. “This is a wake-up call for the need to conserve butterflies and their habitat.”

On the Central and South Coast, the Western monarch butterfly population is also in steep decline.

Pismo Beach State Park recorded just 43 monarchs on Feb. 5. Butterfly season in the area typically ends in mid-February, according to a state park representative, who noted that the number of monarchs recorded during peak season was also low. In November 2024, 556 monarchs were recorded, compared to 16,000 in November 2023.

In Goleta, no monarchs were recorded on Feb. 28 at any of the Ellwood sites, according to the city’s website. Due to the low count, surveys have been reduced to once per month. The population at Ellwood Mesa generally peaks in mid-December and declines after the first significant winter storm, dispersing around mid-March. On Nov. 15, 2024, 34 monarchs were recorded, and on Dec. 2, 2024, just four were counted.

Previous research has identified pesticide use, habitat loss and climate change as the major causes of butterfly declines.

Despite the severe decline in the United States, 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 the previous winter. While monarchs occupied nearly twice as much forest habitat as last year, populations remain far below the long-term average, according to WWF-Mexico and Mexico’s National Commission of Protected Natural Areas.