‘Butterfly man’ finds clues to climate change

Is the climate heating up? A UC Davis lepidoptera detective cracks the case

UC Davis professor Arthur Shapiro is on the lookout for missing butterflies.

UC Davis professor Arthur Shapiro is on the lookout for missing butterflies.

Photo By Ryan Donahue

In a functional classroom in a functional building on the UC Davis campus, Arthur Shapiro sits unassumingly in the corner. Rumpled, wearing well-worn Converse All Star tennis shoes, old jeans and a faded, zippered green hoodie, Shapiro could be just another student, except for his weathered face and bushy gray beard.

In fact, Shapiro happens to be one of the world’s leading butterfly experts, a “biodiversity guru,” as one of the students in the class puts it, or “a walking encyclopedia,” says another—and, as it happens, the mastermind behind one of the United States’ leading indicators of a changing climate as well as a changing landscape.

On this rainy morning, though, Shapiro sits at a right angle to the rest of his students, congenially conducting a graduate seminar on tropical speciation. Well, that is the goal, at any rate.

But first, there are so many other things to mention. The chalkboard stays blank, the walls unadorned, a student’s beakerlike thermos of coffee untouched, and if the chairs had seatbelts, the students would be wise to buckle up because, as is the case in talking with Shapiro, it is quite a ride.

With Shapiro peering owlishly through round glasses at his five students, the nominal topic of biodiversity zooms from the extinct Falkland Islands wolf to moraines to glaciers known as wurms to goat bones as holy relics to St. Ursula and 10,000 virgins to—“Somebody put a duct tape on my mouth and shut me up,” Shapiro says—but too late for that, there are more holy-relic goat bones, then—where were we?—ah, The Island of Dr. Moreau, and, all along the way, alighting on mentions of butterflies, glorious butterflies.

Butterflies, you see, have been Shapiro’s lifelong passion and muse, long before they became for him and the rest of us, in his words, “the proverbial canary in the coal mine of climate change.”

From pupil to pupa

Shapiro first turned to nature and to butterflies as an escape from what he says now was an unhappy childhood. The son of an industrial-chemical salesman, he was reared on the edge of Philadelphia.

“Our street was the last row of brick houses in the city, and across from us it was semirural with wooded lots,” he says.

Shapiro lost himself in those woods, and found himself, too, quickly acquiring an intense interest in the natural world. By fifth grade, he had become fascinated by bugs, particularly butterflies. By junior high, he was taking the trolley to wetlands near the Philadelphia airport to conduct field studies. He delved into books on neo-Darwinism and decided to drop his other passion, meteorology, as a career choice (though he continues to write page-long weather forecasts and posts them for his department in Storer Hall on the UC Davis campus). Instead, by high school, Shapiro had become a sort of butterfly prodigy, competing in national science talent competitions and publishing some of his field notes. He also did well academically, earning a scholarship to the University of Pennsylvania, drawn to the school, he says, because it was home to one of the world’s leading ecologists, Robert MacArthur, who became his mentor and adviser.

After graduating from college at the age of 20, Shapiro immediately moved on to graduate school in entomology at Cornell University. He earned his doctorate in four years and taught briefly at the City University of New York’s Staten Island campus. By the winter of 1971, Shapiro had landed at UC Davis. Also by then, he had married his wife, Adrienne, whom he first wooed with pet moths he kept in his pockets. As the result of an ecology study, he also nearly had a glacial bog in Staten Island named in his honor, until it was accidentally filled in.

The egg stage

New to California, Shapiro was thrilled by its Mediterranean weather.

“I was a carpetbagger when I arrived, and in phenomenological seventh heaven because of the Mediterranean climate,” he says. “We sit at the knife edge between Eastern and tropical climates,” he adds of the area’s winter rainy season and hot, dry summers.

The Western tiger butterfly has returned locally after a 15-year absence. Reasons for its disappearance are unknown.

Photo By Ryan Donahue

With the Mediterranean climate creating an ideal laboratory, Shapiro embarked initially on a five-year study of butterflies, focusing on their ability to adapt to seasonal climate change.

Unlike most butterfly species, which thrive in places with summer rain, those in the Bay Area and Sacramento Valley had already learned to adapt to long, hot and dry summers. The region’s butterfly fauna included those that had migrated here from hot and cold places, along with a few strays that had been introduced by humans.

The Sacramento Valley’s local butterfly species, dependent on certain types of plants, are also relative newcomers, having lived in the region since only about the 1800s. Similarly, the Mediterranean climate itself is also relatively young in geographic terms.

“Nobody knows what was here before,” Shapiro says. “Although we do know the native grasslands were replaced; before Europeans, the color of the grass was grayish-green, not golden in the summer. Forests were also cleared to a few stands of trees near water.”

While juggling teaching, publishing research papers and sponsoring an annual contest that awards a pitcher of beer to the first person who catches a cabbage white butterfly, Shapiro also slowly began establishing a network of field sites where he could monitor different butterfly populations.

Eventually, Shapiro established 11 sites that stretched from Suisun Marsh to Donner Pass to the Sierra Valley on the eastern side of the Sierras. Shapiro’s butterfly corridor followed Interstate 80, making it a sort of butterfly highway, as it rose from sea level to treeline, passing through West Sacramento (home to 58 species and subspecies of butterflies), north Sacramento along the American River (62 species and subspecies) and Rancho Cordova (58 species), and moving from marshy to dry to alpine climates.

As part of this process, Shapiro chose places that were accessible yet unlikely to be changed by such things as a new shopping center or a housing tract, or filled in like his former bog. He also picked sites that had diverse ecosystems, weather and geology. Over time, Shapiro worked up to visiting the sites every two weeks, averaging more than 220 trips a year, with about 44 weeks in the lowlands and 14 weeks in the mountains. So far he has notched nearly 6,000 trips to his Northern California transect. At each site, he meticulously tallied butterfly populations. He also researched local climate conditions as far back as the Gold Rush era, starting with the earliest known records from the 1840s.

As the information and butterfly counts piled up over three decades, it became increasingly clear, and in fact could not be ignored, that things were changing, and alarmingly fast.

The caterpillar stage

By the late 1990s, Shapiro could easily see, as could his graduate students, that major changes were taking place at all of his butterfly field sites, and not for the good.

“There was a shocking decline [in butterfly populations], so much had been lost from just 30 years ago,” Shapiro says. “We could see by [eyeballing] the data what was happening. Eventually, my graduate students took me aside and said, ‘We can’t collect data forever; we have to start analyzing it.’”

At the urging of his students, Shapiro applied for and won a National Science Foundation grant to create a digital database of more than 35 years of field studies. Based on that database, Shapiro and his team statistically quantified a mountain of data on more than 150 butterfly species and subspecies.

The study stood out because it involved a single long-term observer (reducing errors), several sites, multiple species and solid data about the weather. It also became one of the largest butterfly databases in the world and unique in the United States as a long-term gauge of climate change. Shapiro and several co-authors also published their results last year online in the prestigious Proceedings of the National Academy of Sciences.

“Initially, we were really interested in basic questions of community ecology, but there were other things that were unavoidable, and we couldn’t look past it,” says Matthew Forister, a lead co-author and one of the former graduate students who urged Shapiro to transform his butterfly counts into a digital record.

Indeed, from Suisun to the Sierras, butterfly populations are falling fast. Among the species that are going or gone are the large marble, the common sooty wing and the field crescent.

The California Hairstreak butterfly has been seen in the northern Sacramento Valley but is now rare.

Photo By Heather Dwyer, U.C.Davis

Across Shapiro’s transect, the numbers tell a similar story, with butterflies from the uncomfortably hotter lower levels moving up to cooler ground. At his field sites, about the only place where the numbers remain relatively stable for some species is in the mountains. At the tree line, the decline in butterflies is particularly precipitous, because the animals have no place left to go. For all of the regional butterflies, warming temperatures are contributing to a slippery slope of survival.

The warming climate has also caused problems for regional butterfly species by triggering an earlier arrival of spring. In turn, with the highly seasonal butterflies sensitive to day length and temperature change, this has disrupted butterfly life cycles.

In fact, Shapiro and his colleagues determined that of the 23 butterfly species studied near sea level, 16 were emerging earlier than they did 30 years ago. Two species, the red admiral and the sachem, were also arriving about a month earlier than usual.

“Biologically, this was pretty surprising and a mind-boggling amount of change,” says Forister, now an assistant professor at the University of Nevada in Reno.

And, the warming weather was not the only factor adding to the butterflies’ burdens. “The decline is [also] almost certainly tied to development at lower elevations,” Forister says.

“The landscape degradation has been huge,” Shapiro adds, pointing to the suburban developments and shopping centers that have sprouted across the Sacramento Valley in recent decades. “There has been a large loss of habitat and habitat connectivity, and the [landscape] is increasingly becoming more butterfly-sterile.”

As a result, vegetation crucial to butterfly species’ survival—particularly for pregnant females—has disappeared, and existing butterfly colonies have become marooned in increasingly isolated patches of natural habitat. Land-use data, for instance, show that the biggest butterfly losses have been in formerly rural places that have subsequently been developed.

Increasingly isolated butterfly-friendly landscapes have also contributed to an unexpected decline of more-mobile “weedy” butterflies, which depend on different types of habitat for survival. In a chain reaction, or a sort of “butterfly effect” more commonly associated with chaos theory, dwindling populations of “weedy” butterflies (species equivalent to pigeons in birds) at the lower levels also hurts the same species in the Sierras. There, “weedy” butterflies must recolonize every winter from colonies downslope.


So what does all this mean?

From a local butterfly’s perspective, it means a great deal, of course. Some young males, for instance, similar to their human counterparts, like to hang out as a group at watering holes, a practice known as mud-puddling. At night, males and females also cluster together chastely for the evening, roosting on plants and turning toward the east to catch the early morning light.

In the mountains, “hilltopping” is also popular, with large groups of males competing with each other in a quest to rendezvous with females at sunny, easily identified elevated spots. Some of the more ambitious males also travel from hilltop to hilltop.

For other species, the disappearance of butterflies is more of an unknown. Shapiro says that butterflies, which mostly subsist on the nectar of flowers, are not critically important pollinators, or “ecological engineers,” and most plant life is not dependent on the butterflies for survival.

Culturally, butterflies—a cold-blooded species about 60 million years old—have served as colorful fellow traveler and spiritual guide for humans across millennia. Along the way, the species’ capacity for metamorphosis has proved particularly resonant.

As Shapiro notes in his book, Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, “Associations of the soul with butterflies can be found in folklore from Germany and the Balkans to New Zealand and Assam.” Ancient Greeks also thought of the soul as a butterfly. In North America, butterflies can be found on pre-Columbian art. In the Southwest, the Pima people believed their creator was a butterfly who searched the world looking for a good place to put mankind.

The Fritillary butterfly is found in the foothills and mountains, including the Feather River Canyon.

Photo By Heather Dwyer, U.C.Davis

In this day and age, butterflies remain popular, from butterfly gardens in back yards, to butterfly collectors, to butterfly face painting on Chinese New Year, to releasing butterflies at weddings and other festive events.

Whether such traditions will become more commemorative in the future, rather than celebrative of a thriving butterfly community, remains to be seen. Other butterfly species may arrive from places that have become too hot and make their home in the relatively cooler Sacramento Valley. Shapiro says a few stragglers from desert colonies in the southern part of California have already been found locally.

“Big lessons continue to come out of the study,” Forister adds.

Taken for Granite

The recent weather has been a too cold for optimal butterfly viewing, but on a rare dry, sunny day, Shapiro decides to stop by one of his favorite butterfly spots, Granite Regional Park, in Sacramento.

Although the park is not one of his official field sites, Shapiro still likes to visit and get a read on how the butterflies are doing in what is, for them, a relatively new habitat. Shapiro likes the park, formerly a series of rock quarries, because its southwesterly slopes face the sun at the right time for good butterfly viewing, in the early afternoon, and because the quarries remind him of places he explored as a child.

On this afternoon, the sun stubbornly stays behind clouds and the butterflies lay low, waiting for a warm moment to emerge. Even so, Shapiro enjoys stopping to look at the tule marshes, mud puddles, coyote bushes and just-blooming mustard plants. One small tree has a small tumor extending from a branch, known as a gall or oak marble. As it happens, such galls happened to be the original source of India ink, Shapiro says. There also is some sort of connection between them and wasps and the sexologist Dr. Alfred Kinsey.

But before this can be further explored, Shapiro is off, running slightly and pointing down the trail. “There’s one!” he says as an orange sulphur skitters by, dipping and rising.

“Be careful to not let your shadow fall on him; they are pretty sensitive,” says Shapiro, as the butterfly lands in the grass.

In a shirt pocket, Shapiro keeps several pens and a file card. These items have formed the key tools of his landmark butterfly study. At official field sites, Shapiro writes down the butterflies he observes. Back on campus, he then transcribes his observations into log books, which will then be entered into the digital database.

Here in Granite Park, though, Shapiro is happy to chase after the elusive orange sulphur among the animal’s favored plant, hairy vetch. Eventually, the butterfly disappears, having successfully hidden itself in the grass.

“He’s probably looking for a mate, and we are not what he has in mind,” Shapiro says, moving on down the trail.

The former quarries in the park have since been filled in with cottonwoods, marshes and vernal pools. Up along the rim, the pits are surrounded on all sides by industry, with sounds of machinery mixing in with the bird calls. The site has become a small island of butterfly- and wildlife-friendly ground in the midst of a heavily developed landscape.

For the butterflies, such changes continue to pose problems. As a result of a landscape increasingly sculpted by people, butterflies have fewer natural corridors to travel from one spot to another.

“As the habitat becomes more fragmented, so do the butterfly populations,” Shapiro says.

Matthew Forister, a former student of Arthur Shapiro’s, is now a butterfly expert at the University of Nevada.

Photo By Amy Beck

Butterfly burdens

With area butterfly populations continuing to fall, about the only sure thing is that change is taking place.

“Biologically, the change is not very dramatic,” Forister says of the decline in regional butterfly species. “It remains to be seen what will happen, and we are about to find out.”

Forister and Shapiro both point out that the natural world is continually shifting and in transition, though human influence makes these changes more complex.

“The point is not to keep everything the way it was,” Shapiro says. “But [the study] does provide valuable information about our environmental future. I am not so much worried about climate change, though my colleagues and I are of one mind that it is happening, but more worried about denial.

“If nothing else, this tells us how quickly the climate is changing and what kind of impediments we put in the way of species moving. We have to ask ourselves what we can do about [this], and if we want to do something.”

What’s the difference?


• Active by day

• Brightly colored

• Clubbed antennae

• Relatively small body

• Rest with wings held over back


• Active by night

• Dull colored

• Simple or feathery antennae

• Relatively large body

• Rest with wings open, or rooflike