PACIFIC GROVE — The Thanksgiving holiday has historically marked the peak sightings of western monarch butterflies on California’s Central Coast. The peak reached 8,000 this year, a fraction of what the tally should be in a year with a healthy monarch population.
Western monarchs have undergone a sharp decline since the 1980s. Their population hit rock bottom in 2020 with fewer than 2,000 butterflies counted all year, a stark contrast to the hundreds of thousands of monarchs spotted every year in the state over the past three decades and the more than one million spotted in a year as late as 1997. The numbers rebounded in the years following but returned to another alarming low point of about 9,000 in 2024. Conservationists hoped that the milder climate this summer would enable another rebound for the 2025 count. So far, that doesn’t seem to be the case.
“ We know that monarch butterfly populations can fluctuate a little bit. And when you do have natural fluctuations in a healthy population of tens of millions, a couple thousand plus or minus isn’t that big of a deal,” says Natalie Johnston, an Interpretive Programs Manager at the Pacific Grove Museum of Natural History. “But when you have a species that is as threatened as the western monarch butterfly, suddenly those differences are everything.”
The Museum is one of several sites around the Central Coast monitoring local monarch migration. They have counted 226 butterflies as of Friday. The Xerces Society, an international conservation group, will publish a statewide 2025 count in January.
The Museum recommends three main ways people can get involved in monarch conservation: abandoning pesticides, being strategic about planting — native plants are effective and native milkweed, specifically, is suggested for inland Californians — and supporting organizations that do this work.
“And of course, the actions that are taken against climate change help everybody, including monarch butterflies,” Johnston says.
Morale among the Museum’s team of volunteers who perform the count and docents who educate the public about monarchs remains high, despite the disappointing numbers. They show people that, “when they do take action, that they can make a difference,” Johnston says.
Locals can find the Pacific Grove western monarch count updated every week here: http://pgmuseum.org/monarchs.
