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“An encouraging sign”: monarch butterflies return to Central Coast for winter 

Monarch butterflies have returned to the eucalyptus grove at Ellwood in Goleta, CA.
City of Goleta
Monarch butterflies have returned to the eucalyptus grove at Ellwood in Goleta, CA.

Western monarch butterflies are returning to local eucalyptus groves in much higher numbers than last year.

In the past, thousands, if not millions, of monarch butterflies made their way to the coast of California for the winter. They typically spend from October to February in the eucalyptus groves that provide just the right microclimate for their needs in terms of temperature and wind protection.

But their numbers have been dropping in recent years, and last year’s population was alarmingly low.

“Locally, at Ellwood last year, we had 16," George Thomson said. "16 butterflies across about 75 acres.”

Thomson manages Parks and Open Space for the City of Goleta that includes the Ellwood Mesa Monarch Grove. He said this year’s butterfly count began in October.

“We had 20 or so in mid-October, then by mid-November we had 10,000. And with our count today, we expect that number to go up a little bit,” Thomson said.

Every two weeks throughout the winter, a team of biologists sets off early in the morning with binoculars, temperature gauges, and electronic tablets to record data from the area.

Thomson pointed to a cluster resembling dead leaves — it was approximately 30 butterflies clinging to a branch. This one branch held more butterflies than were seen all of last season at Ellwood.

Thomson said the state has recorded around 100,000 monarch butterflies up and down the coast since October. He said there is no clear explanation for the dramatic difference between last year and this year.

“Nobody really knows why the population has come back to the extent that it has this year. I want to preface that by saying that these numbers are still historically low. This is an encouraging sign, but we’re still very concerned about the population overall,” Thomson said.

He said scientists are looking at a variety of factors in search of answers.

“The scientists that are researching this issue, think it’s a combination of climate, increased pesticide use and habitat loss, and then there is some natural variation within the population, but historically we’re at an all-time low, so it’s outside of that normal fluctuation,” Thomson said.

The butterfly grove at Pismo State Beach in San Luis Obispo County is also seeing increased numbers.

“This season we have over 20,000. Last season we only had just below 200 for the entire season,” Danielle Bronson said.

Bronson is with California State Parks and Recreation in Pismo Beach. She said it’s too soon to celebrate but this uptick in numbers is a good sign.

“Even though we’ve had a great year this year, we’re still far from where we were back in the 1980s when, just in our grove alone, we had over 240,000 monarchs,” she said.

Bronson encourages people to visit the butterfly grove and to learn about protecting monarchs. She said the butterflies move around and are easier to see when the temperature is 54 degrees or warmer.

“If you do plan on visiting, I do suggest that you come when it’s a little bit warmer and bring your own binoculars,” Bronson said.

Beth Thornton is a freelance reporter for KCBX, and a contributor to Issues & Ideas. She was a 2021 Data Fellow with the USC Annenberg Center for Health Journalism, and has contributed to KQED's statewide radio show The California Report.
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