"The number of western monarch butterflies overwintering along the California coast continues to remainnear historic lows, according to a new annual count. 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."
"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."
Western monarch populations along California's coast remain near historic lows, with roughly 12,260 butterflies counted at 249 overwintering sites in late November–early December 2025. The total is among the lowest since counts began in 1997, following a long-term decline from population levels in the 1980s. Research indicates about a 10% annual decline since the 1980s driven by habitat loss, pesticide use and climate change. Coastal development and habitat destruction threaten remaining overwintering groves. Hundreds of trained volunteers and partner organizations conduct annual counts, and some communities show that conservation and local growth can coexist.
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