Climbing back from the brink of extinction, the population of Western monarch butterflies wintering along the California coast rose for the second year in a row, according to data released Tuesday, Jan. 31.
A three-week count in November and December 2022, conducted over 272 sites in coastal California by the Portland-based Xerces Society for Invertebrate Conservation, tallied 335,479 of the orange-and-black iconic butterflies, an increase of 36% over the 247,237 counted the previous year.
More importantly, the rebounding species (Danaus plexippus) hit an all-time low of 2,000 in 2020, leaving biologists concerned it would disappear from North America.
“We can all celebrate this tally,” says Emma Pelton, a conservation biologist at the Xerces Society. “A second year in a row of relatively good numbers gives us hope that there is still time to act to save the western migration.”
The modest gain is the highest number since the count in the year 2000. However, the population pales in comparison to 4.5 million or more monarch butterflies counted in the 1980s and 1990s.
“We really don’t think two good years in a row is a trend. It could be a blip, or it could be the beginning of a trend,” said Pelton of Xerces during a webinar on Tuesday, Jan. 31. While the counters and researchers discussed the positive results, they were only cautiously optimistic regarding the fate of the famous butterflies.
“Overall, this winter showed a second year of increasing numbers. It offers hope but it is not a recovery because it’s far from the millions of the 1980s and 1990s,” said Isis Howard, endangered species conservation biologist with Xerces Society, during the webinar.
The largest count in November and December of 2022 was 34,180 butterflies overwintering in a preserve owned by The Nature Conservancy in San Barbara County, the report found. This was followed by 25,710 butterflies at a private residential site also in Santa Barbara County. The third-largest concentration was counted at the Pismo Beach Monarch Butterfly Grove, with 24,128 at their peak.
While the butterfly count took place before a series of atmospheric river storms brought heavy rains, uprooting some eucalyptus trees where the butterflies roost, the question remains whether the delicate species survived the storm damage.
A count done in January will be released sometime in February and could update the numbers.
Emily Johnston, of the Pacific Grove Museum, near a well-established preserve of monarch butterflies, said her team saw butterflies hanging onto fallen branches. There were 14,025 at the Pacific Grove sanctuary, including one monarch that flittered into a supply closet and and clung to a volunteer’s colorful vest, she said.
The boost in wintering insects along the San Barbara and San Luis Obispo county coasts usually means the adult butterflies will spread throughout Southern California. Last year, many local amateur gardeners planted native milkweed (Asclepias fascicularis), which attracts monarchs, becoming a kind of citizen brigade to save the species.
Native milkweed is the only plant monarchs will come to and lay their eggs. Native milkweed has been decimated in the natural environment by development, wildfires and drought. So Xerces and other environmental groups began a campaign to get home gardeners to plant native milkweed to make up for shortages in the wild.
That could be one factor in play that is increasing monarch butterfly numbers in California, experts said.
Brian Brown, curator of entomology at the Natural History Museums of Los Angeles County, said he’s already seeing monarchs near his home in Monrovia. He’s also seen them at a vacation home in Los Osos, which is near the preserve in Pacific Grove.
“I am seeing a lot these days in my home neighborhood,” Brown said on Tuesday. “It is encouraging but you never know. The problem with monarch populations is they go up and down.” The monarchs will be featured at the museum’s Butterfly Pavilion starting in March.
Pelton said scientists can’t pinpoint why the monarchs are rebounding. But she pointed out that drought and land development on habitat has shrunk their population over the decades and they are still not fully recovered.
“The efforts people have made in the last few years (in planting native milkweed) are important and are really helping,” Pelton said.