San Francisco, CA — As California Biodiversity Day approaches, California State Parks Foundation is asking the public to observe and report sightings of western monarch butterflies. California Biodiversity Day is celebrated from September 5–13, 2026. The data from these observations will help scientists understand where these butterflies are at different times of the year and will also help inform the upcoming 30th annual Western Monarch Count.
Millions of western monarchs used to return to coastal California every year, but the population has plummeted in recent decades. Numerous factors have contributed to this decline, including climate change, habitat loss, pesticides, and disease. The annual Western Monarch Count’s most recent survey found a peak population of 12,260 monarchs, the third-lowest overwintering population ever recorded since tracking began in 1997. A Species Status Assessment predicts a greater than 95% chance of extinction for western monarchs by 2080.
“The western monarch butterfly is among the most beloved species in our state,” said Randy Widera, Director of Programs for California State Parks Foundation. “Californians can play a critical role in preserving our western monarch butterfly population by advocating for the protection of butterfly habitats and helping scientists track butterfly locations. We invite Californians to help support monarch butterfly conservation by taking a few easy steps to report sightings.”
As California Biodiversity Day is celebrated from September 5 through September 13, those who want to participate in the process of observing and reporting monarch butterfly sightings can do so with the following steps:
- Download the free iNaturalist app and create an account.
- Snap a photo of a monarch butterfly or caterpillar.
- Upload an observation to iNaturalist.
California’s state parks provide critical habitat for western monarch butterflies. In 2024, California State Parks Foundation released an analysis of 26 years of data on the western monarch butterfly population. This analysis showed that California state parks have hosted at least 20% of the population at overwintering sites. In some years, this figure has reached over 50%. In 2024–2025, Lighthouse Field State Beach, Natural Bridges State Beach, and Pismo State Beach were among the top overwintering sites for western monarchs.
Overwintering is a vital phase in a western monarch butterfly’s life cycle, offering rest and energy conservation before spring mating and northward migration. Overwintering groves provide the specific microclimate the western monarch butterflies need to survive, including protection from the wind and cold, dappled sunlight, and ample nectar sources. Overwintering groves are located in many of California’s state parks, including Natural Bridges State Beach, Lighthouse Field State Beach, New Brighton State Beach, Point Lobos State Natural Reserve, Andrew Molera State Park, Morro Bay State Park, Montaña de Oro State Park, Pismo State Beach, Gaviota State Park, Point Mugu State Park, Leo Carrillo State Park, Doheny State Beach, San Clemente State Park, and Torrey Pines State Natural Reserve.
California State Parks Foundation has helped lead the development of overwintering grove management plans at several state parks. The organization has also funded restoration projects and helped organize volunteer events where participants support the monarch butterfly population through activities like planting native nectar plants. California State Parks Foundation is also advocating for western monarch butterflies to be listed as a threatened species under the U.S. Endangered Species Act. Californians interested in supporting this effort can sign a petition at http://www.calparks.org/
ABOUT CALIFORNIA STATE PARKS FOUNDATION
California State Parks Foundation, an independent, member-supported nonprofit with over 50 years of history, is dedicated to protecting and preserving the California state park system for the benefit of all. We work in parks and in Sacramento with partners, park staff, and policymakers to address the challenges parks face. To make real and lasting change, we are working to build a movement of people who enjoy and advocate for their parks now and for future generations. Learn more at www.calparks.org, or find California State Parks Foundation @calparks on Facebook, Instagram, and Twitter/X, and @californiaparks on Bluesky.
