West Coast monarch butterfly populations hit historic low. This may be the 'new normal'

This is read by an automated voice.Please report any issues or inconsistencies here.

The number of western monarch butterflies overwintering along the California coast continues to remainnear historic lows, according to a new annual count.This adds to growing concern that the population’s long decline may be becoming the norm.Roughly 12,260 monarch butterflies were recorded across 249 overwintering sites during surveys conducted from late November through early December 2025, according to the 29th annual Western Monarch Count released Wednesday by the Xerces Society, a nonprofit environmental organization.

The count relies on hundreds of trained volunteers and partner organizations to tally monarchs as they cluster in coastal tree groves.The total is the third-lowest tally since the count began in 1997, after the 9,119 monarchs recorded in 2024 and the record low of 1,901 in 2020.According to a Xerces Society news release accompanying the new data, western monarch populations regularly numbered in the low millions in the 1980s.Although monarch populations naturally fluctuate from year to year due to weather and breeding success, research led by ecologists Cheryl Schultz and Elizabeth Crone has found that western monarch populations have declined by about 10% per year since the 1980s, driven by a combination of habitat loss, pesticide use and climate change.

Against that backdrop, this winter’s numbers, while slightly higher than last year’s, still fall well below what would be considered stable.“This does appear to be the new normal for western monarchs, and it’s very concerning,” said Dan Fagin, a professor of science journalism at New York University who is writing a book on monarch butterflies.“There’s nothing unexpected about this year’s total, but that in itself is troubling.”Low population levels also make monarchs more vulnerable to short-term stress and long-term pressures, said Isis Howard, a conservation biologist with the Xerces S...