Severe winter storms in California have hit monarch butterfly populations

The population of endangered monarch butterflies is recovering for the second year in a row, but severe storms this winter have killed nearly 60% of the species, according to data released earlier this month by the Xerces Society.

On Thanksgiving, the Xerces Society counted 335,470 butterflies – a dramatic increase from less than 2,000 in 2020. Last year there were 247,000. This is still a drop from the millions in the 1980s and 90s.

“While we do hope we have higher numbers there, it’s also quite normal to have a decline due to crazy climate events,” said Pam Horsley, manager of entomological collections at the San Diego Museum of Natural History.

Not all monarchs survive the winter season, but the usual extinction range is between 38% and 49%. However, the higher population this year gives Horsley hope.

“At the very least, this means there will likely be more survivors,” she said. “So it gives me hope that even if it was a cold, wet winter, there will be more survivors here in the spring.”

Pat Flanagan of the North County Butterfly Farm said monarch butterflies are adaptive, so despite fierce storms, he thinks it looks promising for the species in the spring.

“It wasn’t really what we wanted,” he said. “But I feel that monarchs are very resilient and I expect, especially with all this rain, that we will see a lot of plant material this year.” summer is not only for monarchs, but for all butterflies.”

With all the rain we’ve had, experts say now is a good time to start planting native plants, especially native spurge. This is the only plant where monarch females lay their eggs.

Extreme weather events associated with climate change are usually not good for vulnerable species such as monarch butterflies. Horsley said there was a positive side to the wet weather we had.

“While this may affect the ability of the monarch to survive, at least if the host plants do well in wetter weather, this may give them more opportunities to survive,” Horsley said.

“While San Diego is not known as a huge wintering ground for monarch butterflies, monarchs live here year-round,” said Ann Baldrige, executive director of the Greater San Diego County Resource Conservation Area.

Therefore, it is important to create a habitat for them.

“They need a habitat for both breeding and nectaries where they can go and stock up on food for energy to fly,” she said. “So planting milkweed is the first thing we can do.”

The Resource Conservation Area has packages of milkweed seeds that people can request for free to plant in their gardens.

Baldrige said scientists don’t really know why the monarch butterfly population is rebounding, but it’s good that more efforts are being made to save the species.

The low figure in 2020 “was a huge call to action and a lot of people really came out and supported the monarchs, so many organizations, agencies and individuals are doing a lot of work to create a habitat and support them,” she said.

There has been a big effort in the Central Valley to create more monarch habitats, Baldridge said, because the butterflies’ key wintering grounds are along the Central Coast.