Last year, the mottled orange, black and white wings of 26,000 western monarch butterflies blanketed the forested grove of Ellwood Mesa in Goleta as the species embarked on its annual migration to Central California to escape the chill of winter. But in recent months, the swarms of easily recognized insects have been markedly absent -- an indication of a trend revealing their numbers are "severely down" across the state, according to the Xerces Society, a nonprofit that closely monitors the population as part of its conservation efforts focused on invertebrate species.
As of October, just 34 butterflies were counted at the site, and last week, that number plummeted to just four, Emma Pelton, senior conservation biologist for the organization, confirmed to SFGATE.
"There are essentially no butterflies left there," she said of the preliminary data, noting the organization does not release its official numbers until late January, following its third and final count in December. "But the story is similar across all sites."
Pismo State Beach, which a few years ago saw an unexpected population boom, is down to just a couple hundred of them. The same is true of Pacific Grove, a destination nicknamed Butterfly Town, U.S.A., because so many of the monarchs are known to cluster together on its sanctuary's pine, cypress and eucalyptus trees to conserve energy and seek shelter from the wind. Another private nature conservancy site in Santa Barbara County that usually has the highest counts recorded by the Xerces Society has dwindled down to double digits.
"These are sites that should have thousands and thousands of butterflies," Pelton said. "We're orders of magnitudes off. It's rapid fire, and everyone is trying to make sense of it."
Unusually low seasonal counts have also been reported across the Bay Area, Susan Ramos, a naturalist at Crab Cove in Alameda and one of the regional coordinators for the western monarch counts in Alameda and Contra Costa counties, told SFGATE. Counts at Ardenwood Historic Farm in Berkeley have dropped from 444 butterflies to just 80 of them so far this year, she said. And despite several improvements implemented at Point Pinole Regional Shoreline in Richmond, including enhancing sunlight and planting pollinator gardens, Ramos spotted "only a few flyers here and there -- no overwintering cluster." She was optimistic about the Monarch Bay Golf Club in San Leandro, which had 246 butterflies, as well as the former Skywest Golf Course in Hayward, where 477 butterflies were spotted, though she noted the 126-acre site is "threatened with possible development" in the future.
"The early season counts were low and I was hoping it was just early and more would be on their way. But we had a mid-season count and it also was low," Ramos said in an email, calling the local numbers "super important to capture." At Oyster Bay Regional Shoreline in San Leandro, numbers have fallen from 23 to three butterflies within a year; at Coyote Hills Regional Park in Fremont, 120 butterflies observed last year have dwindled to about a dozen, she added.
With an estimated 7,000 butterflies recorded so far in California, the Xerces Society is anticipating the "second-lowest overwintering population ever this year, due at least in part to record-setting heat and drought in their western range this summer," spokesperson Deborah Seiler told SFGATE in an email. The organization has been conducting biweekly counts during the overwintering season since 1997, estimating that since monitoring began, the western population has declined by more than 95% due to several threats over time, such as the loss of the milkweed its caterpillars eat, the degradation of forests along the coast, and the widespread use of pesticides.
December typically marks the peak of monarch activity, and the organization's trained volunteers have three weeks to descend on more than 250 overwintering sites across California to scout out clusters of the butterflies, Pelton said. Binoculars in hand, they set out early in the morning before the monarchs begin to fly, and look for any factors that could be contributing to their decline, such as whether any trees have been cut down since the last count, or if a wildfire or deluge of rain had swept through the area recently.
Prior to this year, the lowest count was in 2020, when 2,000 butterflies were tallied. The population appeared to bounce back in 2023, with over 200,000 of them flying through overwintering sites. Pelton said the "wild swings" are the product of a population responding to changes in their environment that can have negative impacts, such as loss of shelter from a bad winter storm, but also some benefits. Smaller populations may also experience reduced competition for food and other resources, which can help them recover to higher numbers. Ultimately, the fluctuations give Pelton hope that if the species has struggled before, they can rebound again.
"The bounciness of their population is a blessing and a curse," she said. "Last time we saw this in 2020, we were really doing some soul searching: 'Is it over?' Then we had three relatively good years. That tells us it could take some years for a return, and we could see low numbers for a while. We just need to take part in long-term efforts to help them."
In response to the downturn, the U.S. Fish and Wildlife Service proposed listing the monarch as a threatened species under the federal Endangered Species Act last Tuesday, a major step forward for advocates at the Xerces Society who have been petitioning for the species' consideration since 2014. To aid in conservation efforts, the agency is also drafting a plan to implement 4,395 acres of overwintering habitat for the western population across Alameda, Marin, Monterey, San Luis Obispo, Santa Barbara, Santa Cruz and Ventura counties. Fish and Wildlife is seeking public comment on the proposal, which can be submitted until March 12, 2025.
City and county officials say they're taking action, too. In the Bay Area, one highlight has been UC Gill Tract Community Farm in Albany, where the Sonoma Land Trust and UC Berkeley students have been working to closely monitor the site. With over 100 butterflies counted so far this year, it's been considered a rare "hot spot," Pelton said, due in part to the fact that it has little to no history of pesticide use or development, according to its website.
Meanwhile, George Thomson, parks and open space manager for the city of Goleta, told SFGATE the effects of climate change and the statewide drought have been "magnified" at Ellwood Mesa, which is near the southern half of the monarchs' overwintering grounds. In response, the city adopted a management plan for the butterfly grove after receiving a $3.9 million grant from the California Coastal Commission in 2019. For the past four years, Thomson and his team have been working on a "significant habitat restoration project" using light detection and ranging (lidar) technology to create a 3D model of the grove, mapping out where trees should be planted and where dead wood can be extracted. The latter "doesn't do much to protect the butterflies from wind, it's the leaves," Thomson said, and they're able to use the model to look as far as 20 years out to determine what microclimate conditions they can provide that would be most ideal for the monarchs moving forward.
"If there's not intervention at this level, they're likely to go extinct," he said.
Thomson's staff has been preparing and planting approximately 10,000 native trees and flowering shrubs throughout the grove, getting the community involved with their efforts on Saturday mornings. Thomson said one of the most disheartening things he's heard from children volunteering with their families is that they've never seen butterflies clustering in the numbers he saw 25 years ago.
"It's an existential crisis kind of situation," he said. "But the heartening thing is they're out there trying to make a difference," he said.
Not only are monarch butterflies highly effective long-distance pollinators, they're also a critical part of the food web and serve as a flagship species for the decline of insects, which can be linked to a plummeting bird population and "a broader biodiversity disaster," Pelton said. In addition to planting milkweed and reducing the use of pesticides, she encourages people to participate in community science, recording sightings of monarch butterflies and milkweed using apps like iNaturalist.
"This is information that's being used by researchers in real time," she said. "Everyone can help make a difference."