Western monarch butterfly population reaches its highest number since 2000

The western monarch butterflies reached its highest number since 2000 after more than 200 volunteers reported that a total count of 335,479 individual monarchs in California and Arizona during November and December of 2022. Western monarchs, who winter in California and migrate thousands of miles every year, are counted annually all across the coastal area of California as well as California’s interior and Arizona.

The majority of the western monarch butterflies, 34,180 individuals, was at a private site in California’s Santa Barbara County, while other sites in Santa Barbara, Ventura and San Luis Obispo counties hosted more than 20,000 butterflies. The San Francisco Bay area also saw an uptick in the western monarch butterfly population with around 9,000 individuals counted.

“We can all celebrate this tally,” Emma Pelton, a conservation biologist at the Xerces Society and western monarch lead, said. “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.”

While the population has rebounded, the species is still considered endangered compared to its population numbers in the 1980s when millions of butterflies could be seen in the trees. Scientists estimate the western monarch butterfly population is still down “over 90% from historic numbers in the 1980s and into the early 90s,” Mongabay reported.

“We know we still have a long way to go to reach population recovery,” Pelton said, “and the storms that hit right afterwards mean we’ll start the spring with far, far less than this total.”

While the U.S. Fish and Wildlife Service decided not to list western monarch butterflies as on the Endangered Species List back in December 2020 citing other species are a higher priority, conservationists said “a stronger effort to secure existing overwintering sites and to make them more resilient to the impacts of climate change” is necessary.

“The plain fact is that if we lose overwintering sites in California, we could lose migratory western monarchs,” Isis Howard, a conservation biologist with the Xerces Society and coordinator of the count, said. “Development, eucalyptus removal and tree trimming all need to be managed thoughtfully if we are to leave space for these animals to survive.”

To help play a role in the recovery of the western monarch population, Mongabay recommends these effective changes:

1. Growing native milkweed (Asclepias) plants.
2. Growing a variety of nectar plants, preferably native to your region.
3. Reducing or avoiding the use of pesticides.
4. Encouraging policymakers to support initiatives like the Recovering America’s Wildlife Act and the Monarch Action, Recovery, and Conservation of Habitat Act.
5. Participating in community science projects that monitor monarchs, such as the Western Monarch Milkweed Mapper, Western Monarch Mystery Challenge and the nationwide Integrated Monarch Monitoring Program.

“From planting native milkweed and reducing pesticide use to supporting the protection of overwintering sites and contributing to community science, we all have a role to play in making sure this iconic insect makes a full recovery,” Anna Walker, a member of the IUCN Species Survival Commission Butterfly and Moth Specialist Group who led the IUCN monarch butterfly assessment, said. “It is difficult to watch monarch butterflies and their extraordinary migration teeter on the edge of collapse, but there are signs of hope.”