Last winter, roughly one in five western monarchs counted in California was hanging in a single eucalyptus grove at Natural Bridges State Beach.
In the Xerces Society's mid-season count for 2025, volunteers tallied 2,500 monarchs at Natural Bridges. The statewide total for the same count was 12,260. One grove at the west end of town held roughly 20 percent of the western monarchs counted in California. It did that in a year when it had fewer trees than the year before, and this winter that grove faces a test it hasn't faced in a while.
A Grove That Grew While It Shrank
In June 2025, a fire at Natural Bridges destroyed 15 trees that shielded the grove from wind, according to the California State Parks Foundation. Most of the monarch grove survived. That same season, the count went up. Here is how the Santa Cruz sites compared across the last two mid-season counts in the Western Monarch Count data:
| Site | 2024 mid-season | 2025 mid-season |
|---|---|---|
| Natural Bridges State Beach | 1,400 | 2,500 |
| Lighthouse Field State Beach | 1,406 | 1,095 |
| Moran Lake | 645 | 673 |
| California total | 9,119 | 12,260 |
Together, the three Santa Cruz County sites in that table held about 4,268 monarchs at the 2025 mid-season count, about 35 percent of the state's total. In 2024 they held 3,451, about 38 percent. The state's number rose between the two years, and Natural Bridges accounts for most of the local gain. Lighthouse Field, a short drive east along West Cliff, slipped over the same period.
Even with the increase, the bigger picture is still low. The Xerces Society reported that the 2025 statewide tally was the third-lowest since the count began in 1997. Kirk Crane, a docent at Natural Bridges, described what the grove looked like back then to KAZU:
"We had 120,000 in 1997. You'd go through that grove down there, and they would just be roped with huge clusters the size of you and me."
So 2,500 is a small number next to the grove's history. It is also a big share of what's left in California, and that is why the condition of these trees matters beyond Santa Cruz.
What the Trees Are Doing for the Butterflies
Monarchs spend the winter at coastal groves that shelter them. State Parks describes the Natural Bridges grove as eucalyptus that protects the butterflies from wind. Rhiannon Sims of the Santa Cruz District of California State Parks explained the limits of that protection in the same KAZU report: "They pick the overwintering sites that they do partly for wind protection. But if we have a big storm that comes through, sometimes even being in the grove isn't enough to protect them."
The fire took 15 of those windbreak trees, and some of the work since then has been about rebuilding that buffer. The California State Parks Foundation says its grants supported Groundswell Coastal Ecology's grove enhancement at both Natural Bridges and Lighthouse Field. That work included planting nectar plants, installing trees to shield the groves from wind, and coordinating volunteers. The Foundation also points out the tradeoff behind this kind of work. Most monarch habitat in California is nonnative eucalyptus, which burns easily and harms local ecosystems. Grove managers have to weigh what the monarchs need right now against a longer-term move toward groves of native trees.
Newly planted windbreak trees take years to fill in. This winter, the grove will be sheltering monarchs with whatever cover it has now.
This Winter's Forecast
The Climate Prediction Center's October 8, 2026 ENSO discussion said El Niño was still strengthening, with a strong-to-very-strong event likely through January to March 2027, at better than an 83 percent chance. It also gave an 83 percent chance that the October to December period would be a historic event, stronger than any El Niño on record back to 1950. NOAA added that an event this large makes typical El Niño impacts more likely but not guaranteed. The next discussion is scheduled for November 12, 2026.
That forecast is what worries the people who track these butterflies. "We're concerned that this winter could damage groves, result in more monarch mortality than we've seen in past seasons," Isis Howard, a conservation biologist at the Xerces Society, told KAZU. The station also noted that it's not clear how this El Niño will play out.
The grove is fullest before winter storms usually arrive, and this year the storms are more likely than usual to be strong.
November Is When the Grove Fills
Last year shows how quickly the grove fills up. In its preliminary early-season update, the Xerces Society reported 1,100 monarchs at Natural Bridges as of October 29, 2025. By the mid-season count, the vetted figure was 2,500. The number more than doubled in a few weeks. State Parks says late October and all of November are often the best time to see monarchs at Natural Bridges.
The 2026 counts run on this schedule, according to the Western Monarch Count:
- Early-season count: October 17 to November 1, 2026
- Mid-season count, formerly the Thanksgiving Count: November 14 to December 6, 2026
- Late-season count: December 26, 2026 to January 10, 2027
That puts the mid-season count, the number most often compared year to year, right in the window when El Niño is expected to be building. If you walk the boardwalk in mid-November, you'll be seeing the grove about when this season's official tally is taken. A visit in late December or January could look different, depending on what the storms do in between.
The count itself is an estimate. Volunteers usually work in pairs and survey early in the morning, before the temperature passes 55°F. They scout with binoculars and count individual butterflies, or estimate large clusters by counting a sample and extrapolating. Then they compare their separate estimates. If you want to see the grove close to the conditions counters work in, go on a cool morning.
Planning the Walk
The details from California State Parks for this season:
- Park hours: 8 a.m. to sunset.
- Visitor center: Open daily from 11 a.m. to 4 p.m. from October 1 through January 31, then Friday through Monday from February 1 to September 30.
- Day-use parking: $10 per vehicle, $9 for seniors.
- Getting to the grove: A boardwalk that works for wheelchairs and strollers leads to an observation deck that overlooks the trees.
- Tours: The State Parks page lists monarch tours for school groups from October through January. For public guided walks this season, ask at the visitor center.
Lighthouse Field State Beach makes a natural second stop on the same morning. It held 1,095 monarchs at the 2025 mid-season count, and it's one of the two groves where Groundswell Coastal Ecology has done its enhancement work. Between the 2024 and 2025 mid-season counts, Lighthouse Field went down while Natural Bridges went up, so one outing covers both sides of last year's local numbers.
If you'd like to do more than visit, KAZU's report lists three places to start: protecting habitat, cutting out pesticides, and joining citizen science projects. The Xerces Society publishes the vetted count data each winter, so the 2026 mid-season number for Natural Bridges will show up there after the November 14 to December 6 window closes.
No one knows yet how the grove will come through this winter, which is a good reason to walk it in November. If you're on the Westside and want to swap notes on the grove or anything else happening around town, Megan DeVivo is always glad to hear from neighbors. Let's Connect.
