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Decades ago, he explains, “a short drive down any road in the Midwest or on the Great Plains would yield hundreds of dead bugs splattered across the front of your car. “We’ve dubbed it ‘the windshield phenomenon,’” says Scott Black, executive director of the Xerces Society for Invertebrate Conservation. Still, he and many other scientists have for years reported an alarming absence of these animals in places where they once were abundant. For those that have, “we have virtually no baseline data and very few long-term population studies,” says Shapiro. Of an estimated 3 to 30 million insect species on the planet, only 1 million have been identified by scientists. In the 1990s, hundreds of millions of butterflies made these epic journeys, but their numbers have dropped dramatically, with 80 percent fewer monarchs wintering in Mexico, and California’s winter population down by 99 percent.īeyond butterflies-by far the best known of all insects-how are other six-legged species faring? It’s hard to say. The best known and most beloved of North American butterflies, the monarch migrates up to 4,000 miles round-trip each year, and its large winter gatherings are among the greatest natural spectacles on Earth. Scientists have recorded similar drops in both Sweden and Belgium. In the United Kingdom, a countrywide monitoring effort launched in the 1970s shows that 52 percent of butterfly species have declined in abundance, and the ranges of 47 percent have contracted. A recent paper published in PLOS One reports that butterfly abundance in Ohio has declined by 33 percent during the past two decades. “They’re just gone.”īutterflies are “just gone” from many other places as well. Two other species, the large marble and the field crescent, have become “regionally extinct,” Shapiro says.

Today, there is just one population at a single site along the transect. He cites the common sootywing, a shiny black butterfly with white specks that “once was indeed so common I could walk out of my office and pick larvae off weeds growing in cracks in the sidewalk,” he recalls. To Shapiro, the most surprising losses are of formerly widespread and abundant species.

“Even species at the highest elevations suffered,” Forister says, “and so far, they have not recovered.” At the lowland sites, meanwhile, nearly three-quarters of 70 butterfly species are still declining. According to University of Nevada–Reno insect ecologist Matt Forister, a former graduate student of Shapiro’s who still analyzes much of the project data, “we looked at these mountain sites as refuges where butterflies could escape the pesticides and habitat loss that dominated the lowlands.” But all that changed during a four-year drought that began in 2011. The exceptions were a handful of high-elevation locations. But beginning in the late 1990s, he became aware of a troubling long-term trend: Butterfly numbers were declining at nearly all of his 10 survey sites. It is the longest-running butterfly monitoring project on the continent.įor the first two decades of this ambitious effort, Shapiro focused on annual fluctuations in the insects’ numbers in response to weather and other variables-“what scientists call noise,” he says. Since 1972-for nearly half a century-Shapiro has been surveying butterflies once every two weeks from spring through fall along a transect in north-central California that stretches from sea level to the High Sierra. “There are several species that are even worse off.” Not so well known: “Monarchs are far from the only California butterflies going downhill,” says Art Shapiro, professor of evolution and ecology at the University of California–Davis. Hardest hit are monarchs that breed west of the Rocky Mountains and winter on the coast of California, which have declined to less than 1 percent of their historic numbers. MOST PEOPLE ARE FAMILIAR with the sad story of North America’s monarch butterfly, whose populations have plummeted in the past few decades. For insect identifications and credits, see below.) Our future depends on it.Ĭomprising some three-quarters of all known animal species, the world’s estimated 3 to 30 million different kinds of insects display a dizzying diversity of sizes, shapes and colors. Evidence is growing that insects are in decline, but each of us can take steps to help.