Photo by Suzanne D. Williams on Unsplash
After hitting an all-time low in 2020, western monarch butterfly populations are bouncing back. In North America, these iconic orange and black insects migrate thousands of miles every year. Migration begins in August, and the butterflies reach their overwintering sites in November, where they stay until March.
Eastern monarchs—those whose summer breeding grounds are east of the Rocky Mountains—overwinter in Mexico, while Western monarchs (west of the Rockies) do so in sheltered groves along the California coast.
Generations of butterflies often return to the same groves, or even the same tree. In 2020, the Xerces Society for Invertebrate Conservation recorded fewer than 2,000 butterflies in California. It was a huge change from the tens of thousands recorded in the years prior, and a 99% decline from the millions that overwintered there in the 1980s.
Since then, the migratory route of monarchs has been destroyed by sprawling housing and development, increased pesticide and herbicide use for commercial agriculture, and the eradication of the milkweed they depend on.
Climate change is also a factor in their dwindling numbers. Migration happens in sync with the seasons and the blossoming of spring flowers, but extreme, fluctuating temperatures have disrupted these natural rhythms.
The presence of monarchs in California is considered an indicator of ecosystem health, and their absence shows that climate change and habitat destruction are taking their toll. The butterflies don’t have any state or federal legal protections, and the Western Monarch Count finds that the quasi-extinction risk of monarchs is 72% within 20 years.
However, on October 20, monarch counts on Pismo State Beach Monarch Butterfly Grove and a nearby site totaled roughly 8,000, compared with the mere 300 counted in 2020. The monarch count lasts three weeks, but unofficial estimates put this year’s population at California overwintering sites at around 50,000.
This still represents only 25% of the population that flocked here 5 years ago, but conservationists are encouraged to see these numbers rising.
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