From:The Atavist Magazine by:
Monarchs migrate solo. The first challenge facing the butterfly that Egertson’s son named Flamingo was likely crossing the Cascade mountains running from southern Canada to northern California. Clearing a 10,000-foot peak is well within a monarch’s capability; although the eastern and western migrations rarely mix, butterflies have even been known to cross the Rockies. On cool nights, finding shelter from the wind and other elements would have been imperative. Once the sun set and the temperature dropped below 55 degrees, Flamingo’s powerful wing muscles would become paralyzed; another 15 degrees and he would no longer be able to crawl. If he were knocked to the ground in the night, he could become prey for mice or voles. They would eat his narrow body and leave his wings in the dirt like a discarded costume.
There were also human dangers to contend with, starting with busy highways. Along the eastern migratory route, millions of Flamingo’s kind become roadkill every year; according to one study, collisions with cars in Oklahoma, Texas, and northern Mexico deplete the monarch’s numbers by as much as 4 percent. Out west, researchers see less evidence of significant losses along highways, but the smaller population can little afford any at all. It complicates the picture that one promising initiative to restore monarch habitat is to plant flowers on roadsides, since the land there has few other uses.
After a few weeks, Flamingo probably reached the wide, flat floor of California’s Central Valley. Most western monarchs are funneled through this corridor, which some 40 years ago was an inviting place: a rich patchwork of grasslands, dotted with bright blooms in all but deepest winter, threaded with streams and rivers, and soaked with sun almost 300 days of the year. John Muir famously described the Central Valley as “the floweriest piece of world I ever walked, one vast level, even flower bed.” But in recent decades, industrial farming has ironed out all but the last inches of wild land, replacing ungoverned prairies with perfect rows of produce. Roughly a quarter of America’s food comes from the Central Valley, including 40 percent of our fruit and nuts. The region is also California’s fastest growing in terms of population. The World Wildlife Fund (WWF) estimates that more than 99 percent of the valley’s standing grass consists of green lawns and cereal crops. Cultivation has crowded out native grasslands, with their goldenrod, milkweed, and thistle.
Water is also a scarce commodity. Vast wetlands once fed by the Sacramento and San Joaquin Rivers shrank by more than 90 percent in the past century as the water was diverted to irrigate fields. A seven-year drought, which ended in 2019, dried up even more marshlands, endangering birds as well as butterflies. The northern end of the valley is famous for vernal pools unlike any on earth: Rain fills them in winter, and they evaporate slowly in summer, leaving rings of wildflowers each time the water level drops. The WWF estimates that more than two-thirds of these unique ecosystems have disappeared, either drained for agricultural use or leveled to make way for pastures and fields.
Where Flamingo once would have found water and nectar there were instead gleaming cattle and tidy crops treated with pesticides. Crops like strawberries and almonds are rendered unsellable by even the slightest damage, so farmers make liberal use of chemicals to keep them pristine. When the Xerces Society tested milkweed across the valley, it found pesticide in every sample, including plants grown in private gardens by people who claimed they had never sprayed. Even if Flamingo managed to find food, he risked consuming poison along with his meal.
Monarchs migrate hundreds or thousands of miles every year.
Art Shapiro knows all about poison. He started counting butterflies in 1972. He was new to the West Coast back then—he’d moved for a job in the zoology department at the University of California, Davis, not long after finishing his doctorate at Cornell—but he was accustomed to spending long days searching for insects. Growing up in an unhappy home on the outskirts of Philadelphia, he would slip out the door with a field guide in his pocket and lose himself looking for flashes of color in an undeveloped expanse of land across the street from his house. As a college student in the 1960s, he studied phenology, the scientific term for biological seasonality: how subtle cues such as temperature and sunlight tell fruit trees when to bloom, insects when to hatch, and birds when to migrate. Shapiro began to dream of creating an enormous data set. If he could track many butterfly species over many years—wet years and dry ones, hot years and cold ones—he would be able to see which aspects of a climate exerted the most control over the life cycle.
In California, he selected five sites at various elevations, each with its own diverse ecosystem, and made the rounds every two weeks, weather permitting. He compiled a list of 160 species of native butterflies to monitor, monarchs among them. Unlike scientists who tag monarchs to track their migration, Shapiro’s goal was to compare the size of butterfly populations from one year to the next. The methodology could hardly have been simpler: He visited the same sites on the same schedule and noted the number of butterflies he saw. Since Shapiro didn’t drive, each location had to be accessible by public transportation; he sometimes hiked several miles from a bus stop to get where he needed to go. In those early days, he rarely failed to find his quarry. At a single stop, he would frequently see as many as 30 species. Along with monarchs, there were skippers and sulfurs, swallowtails and painted ladies, henna-colored lustrous coppers and periwinkle Melissa blues.
He planned to do the project for five years, since that was all the time he’d have if he didn’t get tenure. When he was offered a permanent place at the university, he decided to keep going. Gradually, Shapiro added five more sites, until his study covered a large swath of the Central Valley. As local bus systems grew less reliable, he asked graduate students for rides. He became a fixture at gas stations and dive bars all over his route, his annual arrival a welcome sign of spring. We spoke over the phone for this story, but in pictures Shapiro looks like a hermit in a Georgian-era painting—weathered face, wild hair, enormous white beard—except that he’s often wearing a Southwestern-patterned shirt.
After a few decades, he realized that he had inadvertently conducted what might have become the world’s longest continuous butterfly study, rivaled only by one of similar vintage in the United Kingdom. He soon noticed something else: The number of butterflies at his locations was declining. At first, Shapiro wasn’t too worried. Insect populations are naturally “bouncy,” meaning that numbers can dip in years with unfavorable weather and rebound quickly in good years, since each female lays hundreds of eggs. But in 1999, the populations of multiple butterfly species crashed simultaneously, their totals plummeting well below any natural ebb that Shapiro had witnessed before.
Shapiro strongly suspected that the butterflies were suffering the effects of neonicotinoids, a class of insecticides that were introduced in the early 1990s and entered wide usage toward the end of the decade. Neonics, as they’re called, are systemic, meaning that plants absorb them into every cell from bud to stem, and they can be long-lasting, building up year after year and persisting in water and soil even if a farmer stops using them. A growing body of research would ultimately support Shapiro’s hypothesis, showing that even in doses too small to kill outright, neonics shorten the life spans of insects and make them weaker fliers and foragers. Because the pesticides attack a creature’s nervous system, they interfere with navigation, which matters for species like bees, which must find their way back to their hives. The major varieties of neonics are now banned for outdoor use in the European Union but remain popular in the United States, where they have been connected to the widespread collapse of bee colonies.
They also have especially pernicious effects on migratory species like monarchs. Karen Oberhauser of the University of Wisconsin remembers the world before butterflies began disappearing. In 1997, a boom year, she flew to Mexico to see eastern monarchs in their overwintering grounds. She witnessed millions of roosting insects, clustered on every inch of oyamel fir trees, their combined weight bending the boughs. Seeing them gathered together, Oberhauser felt a shiver of fear: They seemed so vulnerable, as if a single blow could erase them from the earth. In the years that followed, she noticed how much habitat monarchs had lost in the agricultural fields that form a large part of their summer breeding grounds. She realized that crops genetically engineered to be resistant to herbicides allowed farmers to blanket their land with chemicals, which eradicated millions of acres of milkweed that once flourished between the soybean plants and cornstalks. Monarch numbers had fallen in tandem. Oberhauser began raising money and advocating for conservation efforts. “A lot of what’s driving monarch loss is changing agricultural practices. Addressing that is going to require policy changes,” she told me.
In California, Shapiro continued to see worrying signs. Monarchs’ seasonal behavior seemed to be shifting. The last generation of butterflies that hatches each fall is called a super generation. During their migration, they enter a state known as reproductive diapause, conserving the energy that other generations expend breeding so they can live six months or more—enough time to make it through winter and breed first thing the following spring. But Shapiro started to hear stories of winter roosts breaking up earlier and earlier. Whereas they used to stay put until March, now they were disbanding in late January or early February. Were they taking their cue from the ever milder weather? Where would they find nectar and milkweed, when most native plants break ground in March at the earliest? Would a freak storm batter them to death or a cold snap freeze them? No one could guess how many migrators might be surviving the winter only to die without finding somewhere to lay their eggs in the spring.
As Shapiro described it, 2018 was the year when “everything went in the toilet.” He witnessed the worst butterfly season he’d ever seen. He counted only 12 monarchs in all of his stops, and for the first time ever he didn’t see a single monarch caterpillar. The once common species had become so rare so abruptly that every individual insect seemed to matter. Would the next year be the one when Shapiro finally saw no monarchs at all?