The Importance of Having Insects

A number of sensational new papers warn of a global insect die-off. Has the apocalypse arrived in California?

May 1, 2019

In 1962, at the dawn of the American environmental movement, Rachel Carson imagined a scene in which the widespread use of pesticide had killed so many birds that the traditional melodic arrival of migratory songbirds to small town America would instead become a “silent spring.”

“No witchcraft, no enemy action had silenced the rebirth of new life in this stricken world,” Carson wrote. “The people had done it themselves.”

Carson, and the science, conservation and government groups that took the problem of DDT pesticide seriously, are often credited as the reason we have pelicans, eagles, osprey, condors, and peregrine falcons flying in California today. As far as slowing what Carson labeled “the fad of gardening by poison,” however, Silent Spring changed little. Global pesticide production has skyrocketed since the 1960s. The use of the pesticides called neonicotinoids increased dramatically in California from their introduction in the 1990s to a high of 450,000 pounds applied in 2015. Habitat destruction has proceeded apace. And meanwhile, in a problem Carson didn’t foresee, the Earth has warmed.

Nearly 60 years after the book’s publication, the last year has seen a widespread revival of popular concern about a silent spring. This time it’s insects, the largely unnoticed yet critical food for birds and much of the rest of life on Earth, that seem to be disappearing. Once again, many of the scientists sounding the alarm also suggest it is human choices to blame.

The concern rests on a number of observations, but scientifically primarily on four recent papers. In the first, in 2017, European scientists showed that insect biomass had declined by 75 percent in measurements taken 27 years apart in a series of German nature reserves. In the second paper, in 2018, scientists showed that arthropods in the soil had declined between measurements 36 years apart in a Puerto Rican rainforest, which the authors attributed to warming temperatures in the tropics. In the third, in January 2019, a research team tallied up all the scientific papers they could find about insect population declines, some 73 in total, to see where around the world the insect decline had been reported. They reported that the answer was pretty much everywhere people had looked, though with a bias toward developed countries, which meant 40 percent of insects were near extinction, with biomass declining at a rate of 2.5 percent per year. The blame this time went to all of the above: pesticide use and pollution, habitat loss, climate change. And then in March 2019, scientists at the University of New Hampshire reported that after examining 119 species of New Hampshire bees in museum collections, 14 were in significant decline.

It appears humanity has triggered an “Insect Apocalypse,” as an eye-popping June 2018 piece in the New York Times Magazine labeled it. “Insect Armageddon,” the scientist behind the German bioreserve study called it in the Guardian. Although the studies and stories have been largely global, in Northern California, the West Coast monarch’s reported 99.4-percent decline from the 1980s to 2018 seemingly fit right into the widespread gloom that we’re witness to things falling apart. “An alarming, precipitous drop in the western monarch butterfly population,” Peter Fimrite wrote in the San Francisco Chronicle in January 2019, “could spell doom for the species, a scenario biologists say could also plunge bug-eating birds and other species into similar death spirals.”

With considerably less fanfare other butterflies mirrored the monarch in 2018. Art Shapiro, a professor of entomology at UC Davis and one of Northern California’s foremost butterfly authorities, started his annual population survey report, “It was a terrible — perhaps even catastrophic — butterfly year at all elevations and no, we don’t know why.” For the first time since he “became butterfly aware” as an eight year old, Shapiro wrote, he didn’t see a single monarch egg or larvae. And what better ambassador for the decline of insects than the beautiful, fragile butterfly?

But the headlines have generated a critique of the science and the reporting of it that manages to be both less apocalyptic and more unsettling, and that boils down to, in essence, if all the insects on earth were declining how would we really even know? Each of the scientific studies, provocative as they are, has methodological limitations that prevent easy global conclusions. The more you’d like to pin the story down to a particular region or particular cause, the harder it becomes. Even the headlines about collapse and apocalypse aren’t particularly novel. If 2018 was a catastrophic year for butterflies, as Shapiro wrote, so was 1986, when John Garth and J.W. Tilden wrote in a field guide called California Butterflies, “Something sinister is happening to California’s butterflies. If one returns to a locality in which a butterfly was found fifty, twenty-five, or even ten years ago, it may not be found there now.”

But the headlines have generated a critique of the science and the reporting of it that manages to be both less apocalyptic and more unsettling, and that boils down to, in essence, if all the insects on earth were declining how would we really even know?

People adjust quickly to find a diminished natural world normal, which is why we try not to rely on personal observation to shape policy. But Shapiro’s transect and the 30-year citizen science monarch counts are two of only a handful of long-term datasets documenting wild insect populations in California. Of the tens of thousands of species of California beetles, moths, flies, bees beyond the honeybee, even butterflies outside of Shapiro’s Sacramento Valley transect line, we have little to no abundance information at all. Those populations could be growing, they could be plummeting toward apocalypse, they could be holding steady. To lose one species might be tragedy, but to lose all the insect species on earth could only be described as carelessness.

“This is the biggest pressing issue not just in entomology but life on earth in general, and it’s challenging that we can’t get any quick answers,” said Michelle Trautwein, an assistant curator and the Schlinger Chair of Dipterology at the California Academy of Sciences.

San Francisco State entomologist Gretchen LeBuhn, who recently re-surveyed eight 15-year-old sites in Sonoma and Napa and found declines, told me she’d been sitting on her data for a few months, unsure what to make of it. She had read the European and Puerto Rican papers, but since the explanations for decline there didn’t apply to Northern California, she said she didn’t expect to find one. Over the phone she pronounced herself “flabbergasted.” Her survey sites are in an agricultural area, but in this area agriculture hasn’t  expanded or changed shape significantly in decades. Pesticide use doesn’t seem to have increased, although the type of pesticides used have changed a bit. It didn’t seem like it was meaningfully warmer, to a bee, in 2018 than it was in 2003. LeBuhn said the only explanation left to her was the most frightening: that there really is some widespread long-term regional decline taking place that has somehow escaped documentation. But why?

There was a pause. “What do you think is going on?” she asked me.

LeBuhn has returned to the North Bay study sites this year to survey again. She plans to hold off on publishing the results until she’s more certain of what she sees. “I don’t want to worry people,” she said. But complicating her basic attempt at understanding is a standard lament: there simply isn’t enough support for serious data collection. She surveyed bees in San Francisco city parks in 2005, for example, but can’t get funding to re-survey them now.

“I feel anxious about it,” LeBuhn said. “But I’m a data person. I feel like there’s enough data to say clearly there are things declining in some parts of the world. Do I think it’s an apocalypse and it’s unrecoverable? I don’t necessarily. We still have enough biodiversity that given the space, it’s completely recoverable. These are insects after all.”

“I feel like there’s enough data to say clearly there are things declining in some parts of the world. Do I think it’s an apocalypse and it’s unrecoverable? I don’t necessarily. We still have enough biodiversity that given the space, it’s completely recoverable. These are insects after all.”

It might be in the news now, but the roots of a global insect decline start decades ago, said Scott Hoffman Black, the executive director of the Xerces Society. Black started his career two decades ago, working on the conservation of rare endemic species. Endemics are tied by their nature to specific and often rare habitats and so, with each new strip mall or road or field conversion, he’d see them disappear. Soon, he says, he and other colleagues noticed the charismatic insects declining, too. Monarchs, other butterflies, bumble bees, honeybees — just about anywhere someone could look and could quantify, they’d notice less bugs.

Small stories kept piling up: drivers weren’t having to clean their windshields after driving through the Central Valley anymore; the buzz at streetlights at night came from the electrical grid, not hovering insects. Shapiro told me his local newspaper runs an annual gardening column every spring describing how to deal with tomato hornworms in the garden. The hornworm, the caterpillar of the five-spotted hawk moth, has by Shapiro’s count been extirpated in Yolo County for years.

Trautwein told me she and her colleagues have watched with despair the destruction of some of the world’s most biodiverse places, from tropical rainforests to mountaintops, knowing what it likely meant for the plant and animal life within, even if they didn’t have the data to show it. Meanwhile globally people are making more insecticide than at any point in human history, according to the United Nations. There’s scientific uncertainty around the exact effects of various pesticides, and industry rejects the idea that agricultural pesticide use is to blame for insect decline, but insecticides, Trautwein said, exist to kill insects. You’d imagine that carpeting the planet with them means something.

Shapiro, too, said there’s more science needed. The Central Valley transect he’s covered for the last 47 years shows a clear decline, but there’s still no obvious cause. Shapiro and University of Nevada-Reno biologist Matthew Forister correlated a precipitous butterfly population drop in the late 1990s with the increasing use of neonicotinoid pesticides, but Shapiro said there’s no corollary yet for what he saw in 2018.

“In fact it’s the lack of rigorous quantitative data sets that’s preventing the translation of an infinite number of anecdotes into real alarm,” he said.

Other butterfly population work in Shapiro’s lab showed a strong weather signal. Butterflies of all types declined through the early 2000s, but then increased during the 2012-2015 drought years to levels Shapiro hadn’t recorded since the ‘80s. When the drought ended, so did the butterfly boom. In fact, they dropped to levels, “as if the decline before the drought had never been interrupted,” Shapiro said.

Stuart Weiss, who’s observed butterflies as part of his wider ecological monitoring work in the San Francisco Bay Area for the last four decades, said the weather in 2018 was particularly tough on western monarchs. An unusually warm dry February caused the first and largest generation of butterflies to fly from their overwintering sites earlier than usual — into a surprising stretch of cold wet weather in March that Weiss says destroyed them. Of course there have been bad weather years before. What changed in 2018?

“Things like the weather year that might have not been a big deal when you have large extensive habitat become a big deal when you have a few hundred acres,” Weiss said. “It’s never just one cause, but piling on top of each other.”

Disentangling all the various causes would take the kind of close descriptive science that entomologists struggle to find funding to pay for. But Black and Trautwein said there’s no reason to delay action.

“The verdict is in,” Black said. “Some people point out we don’t have data for this spot. We’re never going to have data for every spot. We make all sorts of decisions for society based on some uncertainty. But I think we’ve gotten to a point where there isn’t a debate anymore.”

bay checkerspot
An endangered bay checkerspot rests in a protected area of Coyote Ridge. (Photo by Eric Simons)

San Francisco, once famous in lepidoptery circles as the home of the first human-caused butterfly extinction, is now home to a number of projects intended to help multiply insects.

Last year’s cold spring was a tough one for Mission blues, Weiss said, but the city’s signature endangered butterfly persists in a stronghold on San Bruno Mountain and in pockets on Milagra Ridge and the Marin Headlands. After Weiss and colleagues spent several years restoring them, they also still fly on Twin Peaks, where they’d been extirpated following the rainy 1998 El Niño.

The Bay checkerspot butterfly, which Weiss has monitored closely for 35 years, hit a record low population on parts of Coyote Ridge early in 2018 — then rebounded. “That very same weather sequence that nailed the monarchs was good for the checkerspots, so we’re seeing big increases across the board in 2019,” Weiss said. “Generalization is really hard to make. So much depends on the exact timing, when the precipitation and temperature swings occur.”

Weiss also worked with lepidopterist Liam O’Brien and Presidio Trust ecologist Jonathan Young to successfully restore variable checkerspots to the Presidio in San Francisco. The striking black-and-red butterflies are common statewide but had almost entirely disappeared from San Francisco until the restoration project. O’Brien has worked to increase habitat for the coastal green hairstreak butterfly in western San Francisco, with the result that the butterflies are hanging on in the Sunset District and now even flying into new areas in the eastern parts of the Presidio. The Presidio recently made headlines again when a silver digger bee population bloomed in a restored area. “Thinking globally I get really depressed,” Weiss said. “Acting locally I get a modicum of hope.”

You don’t have to be a scientist or lepidopterist, Black said. Native gardens help. Planting pollinator friendly nectar plants helps. Replacing lawns helps. Reducing pesticide use helps. Installing hedgerows helps. Community science programs help. Caltrans changing the way it mows roadside weeds helps.

“This is a societal issue at all levels,” he said. “There are actions whether you’re federal government, state government, local government, farmer, public lands manager, individual in your own life, or a researcher. We don’t have perfect data on the drivers. But we have enough.”

“Thinking globally I get really depressed. Acting locally I get a modicum of hope.”

The seeming magic of Carson’s Silent Spring was that it wrought a real cultural change. Millions of people accepted her logic and desired to try to stave off the bleak future Carson imagined. As the environmental movement took hold the following decade saw the Clean Air and Water Act, the creation of the Environmental Protection Agency, the Endangered Species Act, and the National Trails Act. But some argue the ferocious counter-attack to Carson’s book and subsequent congressional testimony helped create the blueprint for the 21st century’s paralyzing partisanship on environmental issues. “The well-financed counterreaction to Carson’s book was a prototype for the brand of attack now regularly made by super-PACs in everything from debates about carbon emissions to new energy sources,” wrote Eliza Griswold in a 2012 New York Times Magazine piece examing Carson’s legacy.

It seems likely Silent Spring also pioneered a template for communicating environmental problems to the public: lead with the dramatic imagery of the worst-case scenario and plan on fear inspiring action. The template has been repeated over the years, from Silent Spring to The Day After Tomorrow to “A World Without Bees” to The Uninhabitable Earth. Yet considerable and critical nuance exists. And what the hyperbole around insect decline ultimately masks is how little even scientists have described, and how complicated the moral choices can become around solving modern global problems. “All the rhetoric about the extinction of honeybees is just hype — none of the serious scientists working on this thinks honeybees are vanishing,” Nathanael Johnson once wrote in Grist about media coverage of the mid-2000s “beepocalypse.” “But the hype isn’t necessarily a bad thing: It’s gotten people interested in the pollinator problem — and it really is a problem, even if it’s not an existential problem.”

So can people muster the energy to respond to yet another apocalypse cycle? Can they do so on behalf of insects? Creatures so typically lacking in charisma that they’re barely noticed, barely described, barely studied? Go to a Home Depot on the weekend and you can see dozens of people browsing the household pesticide aisle, where a sign advertises a conventional, popular three-step approach to insects: “Kill the Bugs You See. Kill The Bugs You Don’t See. Keep the Bugs from Coming Back.” In late April, when western tussock moth caterpillars bloomed in the South Bay, the city of Mountain View sprayed them with pesticide because the insects — “the worst kinds of visitors: irritating, destructive and back for another visit,” as a Mercury News story described them — were annoying residents with what an expert called “aesthetic damage.”

When I called Weiss to ask what non-scientists could do to help insects, his off-the-cuff answer revealed plenty: “Pay attention.”

“When you start talking about the really broad scale picture, where all these common and redistributed species collapsing, whole insect faunas just crashing, it’s kind of hard to figure out what to do other than re-mapping our agriculture, stopping climate change, cleaning up the air,” Weiss said. “Just whole-scale changes to the way we live.”

Black said he didn’t want to sugar-coat the seriousness of the situation, but also didn’t think it was hopeless. “We’ve gone to the moon,” he said. “We beat Hitler. If society wants to do things it can.”

Carson’s line from Silent Spring, “The people had done it themselves,” recalls another of the famous lines in environmental journalism, from Elizabeth Kolbert’s 2006 climate change book Field Notes from a Catastrophe: “It may seem impossible to imagine that a technologically advanced society could choose, in essence, to destroy itself, but that is what we are now in the process of doing.”

Conservationists describe dire consequences for choosing not to act on behalf of the unseen environment. Insects are the basis of the global food chain and the pollinators of too many critical food staples to count. Whether you’re an insect-eating bird or a person in a city who swats every bug that makes it into your house, life on Earth relies on the things. Their apocalypse would ultimately be a human one, too.

“Plants and insects are the fabric of the planet and all these other animals are benefitting from and living off that fabric,” Black said. “And we are tearing it unmercifully.”

About the Author

Eric Simons is a former digital editor at Bay Nature. He is author of The Secret Lives of Sports Fans and Darwin Slept Here, and is coauthor, with Tessa Hill, of At Every Depth: Our Growing Knowledge of the Changing Oceans.