Western Monarch Thanksgiving Count Tallies Over 330,000 Butterflies Before Storms Batter Overwintering Sites

Figure 1. Total monarchs reported and number of overwintering sites monitored for the Western Monarch Thanksgiving Count from Nov. 1997 to Dec. 2022.

Season highlights

Motivated by a surprising rebound in 2021, volunteers’ excitement continued to grow when early reports hinted at a consecutive year of improved numbers. 2022 ended up being the biggest volunteer engagement year yet, with over 250 people participating and a return to in-person trainings after limited opportunities during the pandemic.

The largest individual monarch count was 34,180 at an overwintering site in Santa Barbara County owned by The Nature Conservancy. (The site is not open to the public.) The second largest count was 25,710 butterflies at a private residential site in Santa Barbara County. Pismo State Beach Monarch Butterfly Grove had the third largest monarch count and is open for public viewing, with 24,128 butterflies reported at its peak.

As is typical, the Central Coast continued to host a majority of the largest sites and overwintering monarchs, with over 130,000 butterflies reported in both Santa Barbara and San Luis Obispo Counties. The Bay Area witnessed a comeback from last year with more than 8,000 butterflies reported in surrounding counties such as Alameda, Marin and Solano.

Additionally, seven newly-recognized overwintering sites were included this season, hosting a combined total of over 15,000 butterflies.

While the numbers are hopeful, this isn’t yet population recovery

This season’s results are a welcome reprieve from a total of less than 2,000 individuals counted in 2020 and even modestly larger than the nearly 250,000 in 2021. 335,479 is squarely back into what was considered “normal” in 2000-2017.  However, even with these relatively good numbers, migratory western monarchs have still declined more than 90% since the low millions seen in the 1980’s and 1990’s.
“We can all celebrate this tally,” says Emma Pelton, a conservation biologist at the Xerces Society and western monarch lead.  “A second year in a row of relatively good numbers gives us hope that there is still time to act to save the western migration. That said, we know we still have a long way to go to reach population recovery and the storms that hit right afterwards mean we’ll start the spring with far, far less than this total.”

Dr. Elizabeth Crone, professor and quantitative ecology at UC-Davis, likens the changing numbers to trying to predict traffic lights. “Given two relatively good years in a row, it’s tempting to think that the rate of change in monarch populations might have suddenly switched from decreases to increases. However, this kind of change is hard to detect for insects like monarchs, because for butterflies – like many insects – the yearly rate of change varies a lot from year to year.”

“When something varies a lot, it takes a while to know the overall trend.  Think about driving down a highway – if you see two green lights in a row, do you assume they are all green and keep going through the next ones without looking? Probably not.” Dr. Crone explains more in her blog that gets into the nitty-gritty of the math behind western monarch population estimates and trends.

The decades-long decline is due in large part to threats such as habitat loss at the overwintering sites and breeding grounds, exposure to pesticides, and the compounding effects of climate change. Much work is now underway to reverse some of these stressors, particularly through planting milkweed and nectar plants, by a wide range of people such as agencies, everyday native plant and monarch enthusiasts, NGOs, and tribes.

These small but collectively powerful changes to rewild our landscapes for monarchs and other wildlife are deeply inspiring. The challenge now is ramping up these efforts to a much bigger scale and engaging in the harder issues like pesticide use, climate change resilience, and doing the slow, important work of protecting and restoring hundreds of overwintering sites.