By: Charis van der Heide in The Atavist
October 2019, if he survived that long, Flamingo might have faced fire. In Sonoma County, along the Central Valley’s western edge, the season’s worst wildfire consumed almost 80,000 acres. Acrid smoke blanketed much of the Bay Area. What does a monarch make of a forest fire? Does it waste precious energy flying around it, or risk getting caught in the conflagration? Still heading south, Flamingo might have ridden the same winds that carried embers across the landscape, wisps of fire that shone even more brightly than his vivid wings.
A few weeks after the Sonoma fire died down, I was preparing to fly to California, too. I had arranged to join an annual effort, organized by the Xerces Society, to monitor western monarchs in their winter habitat—groves where butterflies, in an unsolved mystery of migration, return to the same roosts year after year. Some coastal cities have built around these stands of trees, even if they’re in the middle of town. The first scheduled stop on my itinerary was Ellwood Mesa, a sandy bluff of eucalyptus groves just west of Santa Barbara. But by Thanksgiving morning, it too was in the path of a wildfire. Thousands of people in the surrounding county had evacuated. “There’s no way anyone can take you there,” a municipal employee told me when I called from my home in Boston. Ellwood Mesa was vulnerable to stray embers and to mudslides. When I asked if I could go alone, there was silence on the other end. “There are signs telling people to enter at their own risk,” the employee said finally.
I hung up feeling thwarted. My husband tried to comfort me: Even if the fire interfered with my plan to see a species imperiled by climate change, didn’t that only prove my story’s point? I packed a bag and boarded my flight. I landed in Los Angeles and turned on my phone to find a text from another city employee: A snowstorm had dampened the blaze. I could go to Ellwood Mesa after all.
Xerces calls its annual monitoring effort the Thanksgiving count because it takes place over three weeks in November and early December. More than 100 volunteers visit upwards of 240 sites where monarchs are known to roost. The count is not unlike Art Shapiro’s work—volunteers note every butterfly they can find, then tally the numbers into a single snapshot of the total population that made it to the coast for the winter. If they see any with tags—a rare, exciting event—they can compare the serial number with an online database and determine where the butterfly came from.
In 1997, its first year, the count recorded more than 1.2 million monarchs. Two years later, that figure fell to fewer than 250,000, despite an increase in the number of sites being monitored. Though the population still fluctuates, it hasn’t broken 300,000 since 2000. It plunged to the historic low of 27,218 in 2018. Volunteers visit most count sites only once; if a site is subject to more frequent monitoring, Xerces uses the highest number observed in a single day. Between this and the fact that some butterflies might be spotted twice if they move between neighboring groves, the final tally is more likely to overestimate the monarch population than to underrepresent it.
Once upon a time, Ellwood Mesa attracted more than 100,000 butterflies each year. When I pulled into the site’s parking lot on a Tuesday morning, the sky was overcast. The clean, sweet smell of eucalyptus washed over me. Ellwood Cooper, who once owned this land and for whom the site is named, was a rancher and horticulturalist who helped introduce eucalyptus to the United States. He raised his first trees here in the 1870s. Cooper envisioned the quick-growing eucalyptus as an invaluable source of lumber. It turned out to be brittle and prone to decay, but it did provide an ideal winter home for monarchs, which were observed on the West Coast in growing numbers as eucalyptus spread in the late 19th century. Today, the tree is widely considered a scourge on the landscape. With its shaggy bark and fragrant oil, it is quick to catch fire. But it is also monarchs’ preferred home for the winter; though the insects roost in other trees, such as cypress, they choose eucalyptus groves over forests with exclusively native species. This has put monarch advocates in the odd position of trying to protect a beloved native butterfly by fighting to plant a despised invasive tree.
The volunteer coordinator for the monarch count in Santa Barbara County was a woman named Charis van der Heide, a monarch biologist and environmental consultant for the city of Goleta. She wore a straw hat and hiking boots, and the rest of her attire was dotted with images and emblems of butterflies: a patterned scarf at the neck of her purple parka, a crocheted keychain dangling from her backpack. I followed her down a sandy path into a grove of trees, where the light grew dimmer and the smell heavier and loamier as we followed a muddy streambed. The ground was blanketed with strips of gray bark—“eucalyptus are messy,” Van der Heide said—but many of the branches above us were bare. According to Goleta officials, one in five trees here died during California’s long drought. Of those that remained, many were ailing. Giants 180 feet tall leaned against their neighbors or bent into archways over the path.
Changes in the grove have profound consequences for monarchs. Butterflies choose where to roost with extreme sensitivity. New generations not only go to the same groves and trees as the previous year’s butterflies—they alight on the same branches. They seek a precise microclimate, a perfect alchemy of humidity, temperature, wind speed, wind direction, and light. Every time a tree falls, the delicate balance shifts.
We entered a clearing. Van der Heide, who is in her late thirties, with wavy chestnut hair and a broad, friendly face, pointed out the features that once drew monarchs here. Perhaps because they are meandering fliers—they flap-flap and glide, flap-flap and glide—they choose groves with high, vaulted ceilings that are “cathedral-like,” Van der Heide explained, gesturing upward. The natural architecture gives them space to flit and float. But a thinning canopy may not provide sufficient protection from winter storms. The grove we stood in was once enclosed on three sides by thick walls of trees; now trunks crisscrossed the forest floor, leaving openings everywhere.
Van der Heide told me that she wanted to plant more eucalyptus where we stood. The controversy surrounding that approach didn’t bother her. “We conserve what we love,” she said—even if a favorite natural phenomenon might not exist as we know it without human influence. She echoed Oberhauser’s point about flagship species, arguing that fighting for monarchs could help a wide array of pollinators that share their habitat. “Having a little pragmatism about what people can get behind can serve you in a larger way,” she said.
But even with new eucalyptus to draw them, would the butterflies return in large numbers? As the climate changes, many species are expected to shift their habitat ranges northward and upward, to higher elevations, chasing the conditions for which they’ve evolved. Monarchs might soon abandon the known groves altogether. Maybe they already have. Some count volunteers told me that, in their most optimistic moments, they imagine the butterflies aren’t declining—they’re hiding, and we just have to find them. But it’s not clear where exactly they could have gone. “If you look in the hills, we don’t have trees up there,” Van der Heide told me. “They’ve all burned.”
Charis van der Heide