This article was originally published by Mongabay and is republished with permission.
- Recent studies from Germany and Puerto Rico, and a global meta-study, all point to a serious, dramatic decline in insect abundance. Plummeting insect populations could deeply impact ecosystems and human civilization, as these tiny creatures form the base of the food chain, pollinate, dispose of waste, and enliven soils.
- However, limited baseline data makes it difficult for scientists to say with certainty just how deep the crisis may be, though anecdotal evidence is strong. To that end, Mongabay is launching a four-part series — likely the most in-depth, nuanced look at insect decline yet published by any media outlet.
- Mongabay interviewed 24 entomologists and researchers on six continents working in over a dozen nations to determine what we know regarding the “great insect dying,” including an overview article, and an in-depth story looking at temperate insects in the U.S. and the European Union — the best studied for their abundance.
- We also utilize Mongabay’s position as a leader in tropical reporting to focus solely on insect declines in the tropics and subtropics, where lack of baseline data is causing scientists to rush to create new, urgently needed survey study projects. The final story looks at what we can do to curb and reverse the loss of insect abundance.
In recent months a debate over whether a global insect apocalypse is underway has raged in the mainstream media and among researchers. To assess the range of scientific opinion, Mongabay interviewed 24 entomologists and other scientists working on six continents, in more than a dozen countries, to better determine what we know, what we don’t, and, most importantly, what we should do about it. This is part one of a four-part exclusive series by Mongabay senior contributor Jeremy Hance.
Dust stirred up by the wind turns a Kenyan sunset deep scarlet. Then, as day fades to night, millions, maybe billions, of insects, fly to the artificial lights of homes found at the edge of the bush. One of those residents is Dino Joseph Martins, and while his evidence is anecdotal, the entomologist is a highly qualified observer. Martins has vivid recollections of a time when the abundance of insects swirling around the lights illuminating his outdoor dinner table were staggering.
“You would struggle to sit down to eat your supper because you would have endless beetles and [flying] things falling in your bowl of soup,” he said. Today, “that happens far less.” Now, dinner in the African bush may be a pleasanter affair, but it’s much more disquieting.
Martins, the executive director of the Mpala Research Center, was born and raised in Kenya. As a child, he recalls visiting forests during the wet season that were filled with “tens of thousands of butterflies and other things lining the paths and the roads.” He says you can still find the same kinds of insects in those same forests nowadays, “but in far, far fewer numbers.”
“I just wish we had collected [abundance] data more robustly earlier on, which we hadn’t done,” says Martins. This dearth of baseline data on insect abundance, everywhere around the globe, lies at the heart of an urgent question: is the great insect apocalypse underway, or not? And if it is, how bad is it, where is the crisis most acute, and how can we best respond?
“Now, of course, we should start,” Martins adds. “That’s where we are at.”
‘The little things that run the world’
Humans like to think we run the world, believing in our omnipotence. But while we shape and engineer — make, muddle and destroy — we are not, according to scientists, the world’s ultimate controllers. That role clearly falls to insects, “the little things that run the world,” as E.O. Wilson, the world’s pre-eminent entomologist, told us back in 1987.
Insects may be tiny, but they are mighty and superabundant. British entomologist and ecologist C.B. Williams once estimated a population of one million trillion insects on Earth at any given time. They are everywhere that there is land and sky — intimately involved with everything.
Insects tend to every square centimeter of living soil; they aerate and fertilize; they breakdown the billions of bits of organic debris and waste that other Earth residents produce, disposing of everything from leaf litter to elephant dung. Insects are the original recyclers, digesting dead wood and dead bodies. They also reside at the base of the food chain, feeding tens of thousands of birds, mammals, reptiles, amphibians, fish — and, by extension, us. More than 300,000 known plants are pollinated by animals, most of them insects.
It’s estimated that all the world’s arthropods, a group that includes insects, arachnids, millipedes, centipedes and crustaceans, weigh 17 times more than the planet’s 7.5 billion humans.
Take away this vast mass of crawling, fluttering, skittering insects — comprising maybe 90 percent of all animal species — and you’re truly staring planetwide ecological breakdown in the eye. Waste will pile up; soil will shed nutrients without replacement; animals will starve; and potentially hundreds of thousands of plant species will vanish. Extinction would stalk the land like a famished beast, and the future of humanity would be at stake.
“Think of a meal reduced to wind-pollinated crops — the bread will stay, [but] fruits and vegetables and most of the meat will be gone,” says Axel Ssymank an entomologist with the German Federal Agency for Nature Conservation, who pointed out, for example, that cocoa is “exclusively dependent on the pollination of small midges.” Imagine: a world without these unsung, unseen midges is a world without chocolate — forever.
“We may not always see or understand the intricate ways that [insects] pull and hold ecosystems together, but we know enough to understand that even if we don’t see those roles … they’re key,” says Michelle Trautwein, an expert on flies and assistant curator of entomology with the California Academy of Sciences.
“The Insect Apocalypse is Here,” declared a New York Times Magazine story by Brooke Jarvis at the end of 2018. That piece took a behind-the-scenes look at a study out of Germany that put concrete data behind something researchers had been reporting anecdotally for years. The groundbreaking research found that flying insects fell by 75 percent in just 27 years in 63 nature reserves all across Germany.
Let’s be clear: this wasn’t a story about colony collapse disorder, or pollinator decline, the diminishment or extinction of one particular species, or even a whole family of insects. The German research showed that the abundance of all flying insects — wasps, flies, butterflies, bees, dragonflies, beetles, etc., etc. — had plunged dramatically. Or maybe dramatically isn’t forceful enough: precipitously.
The study did not find a direct cause for why this happened, but scientists believe the drastic decline is linked to agriculture intensification (including a loss of wetlands, cover crops and hedgerows that once supported insects in European farming areas), along with habitat loss and pesticide use. The researchers didn’t point their finger at climate change, but others have, especially in the tropics.
What scientists do know is the urgency with which we need to respond to this new data. “We need to take action right away. A world without insects is unimaginable,” says study co-author Hans de Kroon, a plant ecologist with Radboud University in the Netherlands. “It is really not possible to sit back and say, ‘Well, you know, we need a little more information.’”
For years, entomologists have talked among themselves about strange goings-on: car windshields no longer covered with dead bugs, researchers’ insect traps catching fewer and fewer specimens, and, as Martins pointed out, dinners in the bush getting quieter.
“There is nothing new about [the decline],” says Daniel Janzen, who has been studying insects in the tropics since the 1960s with the University of Pennsylvania. “All that is new is today’s publicity hype and hand wringing.”
Janzen, now 80, could be called the Cassandra of Insect Decline; he’s been talking about this threat longer than pretty much anyone else, with few heeding his warnings.
But the study in Germany couldn’t be ignored, as it rested on meticulous surveys by amateur entomologists since 1989, providing the first hard data demonstrating a full-scale, across-the-board decline in insect abundance everywhere researchers looked.
Learning to count
Part of the reason for the German study’s novelty, and arresting surprise, is that it looked at something we, as humans, had long ignored. From the very beginnings of science in the Enlightenment, insect research focused almost solely on identifying new species, understanding their ecological connections and describing their bizarre natural histories (think of cicadas that spend 17 years underground before emerging for just a few weeks; or the hyper-segmented social structures of ants with one queen to rule them all; or mayflies that hatch, mate and die in less than 24 hours).
“The main problem is that ecologists and entomologists typically do not count insects,” says Vojtech Novotny, an entomologist at the University of South Bohemia in the Czech Republic, who specializes in the insects of Papua New Guinea. While scientists may count species, he says, “quantitative information on insects … or large important taxa over time is surprisingly rare.”
When insect numbers were monitored in the past, the research often focused solely on charismatic species, or groups of species in wealthy countries, such as monarch butterflies in the United States. But rarely, if ever, did scientists count entire populations in the Insecta class across a wider environment as did the 2017 research.
The study in Germany was not to be the last. In 2018, another paper was published examining a different part of the world, with arguably even more frightening implications. In Puerto Rico, researchers returned to a protected reserve and replicated an arthropod biomass survey (the measurement of the total mass of creatures) done in the 1970s. They found that total arthropod biomass had plunged by 10 to 60 times compared to 40 years ago. Disturbingly, but hardly surprisingly, researchers also found that birds, lizards and frogs that depend on insects had seen their numbers fall in response to declining prey.
“People just didn’t expect it,” says lead author Bradford Lister, a biologist at the Rensselar Polytechnic Institute in New York. “It was a hidden connection to the further degradation possible of tropical rainforests.”
The Puerto Rico study linked the precipitous decline to climate change. The researchers theorized that unprecedented heat waves wiped out the tropical insect groups nearly wholesale.
The pairing of these two studies, one from temperate Europe, the other from tropical Puerto Rico, both from protected areas, left many wondering if the insect decline was indeed global — and hitting species across all families.
“What we are measuring is likely only the tip of the iceberg,” says Helen Spafford, an entomologist previously with the University of Hawaii.
Things get controversial
Then this April, a new paper hit, a meta-study analyzing the findings of 73 insect studies worldwide, with its authors claiming insect abundance was falling at a rate of 2.5 percent of total global biomass every year. The paper’s findings proved good grist for the mainstream media mill, but within a month, no less than three additional papers dropped, each heavily criticizing the meta-review (see here, here and here).
Scientists criticized the paper for multiple reasons: for searching papers only for “insect decline” and not populations on the rise; for conflating extirpation with extinction; for mixing statistics from vastly different studies; and especially for drawing global, large-scale conclusions on what everyone agrees is a drastic dearth of insect data. The study was ultimately dubbed by many as alarmist.
“My criticism of that paper is that they lumped together studies with very different protocols and came up with their estimate of decline by averaging across studies that measured different things,” says Tyson Wepprich, a postdoctoral research associate at Oregon State University, who is studying butterflies in Ohio.
Trautwein says the meta-study was “opportunistic” but not necessarily in a negative way. “The studies that they all pulled together weren’t ideal. They weren’t all focused on [the] question that the paper was asking, but at the same time, that’s the data that’s available now. This is a decent estimate with what exists right now.” She contends that the paper should be seen as a “red flag” on insect decline.
The controversy concerning the meta-study was arguably made worse by reporting in the Guardian newspaper, widely read and touted on social media; it declared that the 2.5 percent annual decline of insect biomass, as reported by the paper, “suggest[s] they could vanish within a century.” The article seemed to claim that the entire global class of Insecta could be wiped out as early as 2120 (even though an annual decline of 2.5 percent in perpetuity would never result in zero).
Nearly all of the 24 entomologists and scientists Mongabay interviewed for this series disagreed with the idea that insects will entirely go extinct. Pedro Cardoso, a University of Helsinki ecology professor and lead author of a paper critiquing the meta-study, called the Guardian article’s claim “absurd”; Tratwein dubbed it “far-fetched”; while Janzen called it “stupid and silly.”
Researchers emphasize that insects have been around for at least 400 million years — six times as long as primates. They’ve survived four mass extinction events (we haven’t endured one yet — though many agree we are causing the sixth).
“There are insects that live in the vents of volcanoes, deep in caves, on the top of the highest mountains in glaciers, in hot springs that would dissolve a mammal should it even think of stepping in there,” says Martins. “We shouldn’t go too far and say we’d wipe insects out. I don’t think we could even begin to try.” Or, as numerous entomologists told me: humans will go extinct long, long before all insects do.
However, when I reached out to the lead author of the controversial meta-study, Francisco Sanchez-Bayo, an ecologist with a specialty in pesticides at the University of Sydney, he stood by the Guardian’s assertion, noting that the journalist “did not say they could vanish ‘completely.’” He pointed out that the journalist was simply extrapolating based on the data found in the paper: a 2.5 annual decrease in insect biomass, if carried forward steadily, would lead to a near-zero value for insects. He adds, though, that such extrapolations should be viewed “cautiously.”
Sanchez-Bayo further defended his research by noting that all the surveys reviewed in his paper “considered all species in a taxon, irrespective of being on the rise, remaining stable or declining … Not a single study was focused exclusively on declining species.” In addition, he says more than half of the surveys reviewed in the meta-study were “obtained from references cited in other reports.”
The heart of the problem
In some ways, the heated debate over this particular mega-survey is academic and arguably a distraction. Whether insects may be vanishing at a rate of 1 percent or 2.5 percent annually, or somewhere in the middle, it’s still catastrophically too much. Even as some scientists question the review’s direst conclusions, none said we shouldn’t be concerned, sitting back and doing nothing.
Here’s the crux of the matter: when asked how they would rate the insect abundance crisis on a scale of 0 to 10 — 10 being direst — the answers Mongabay received from researchers on six continents ranged from 8 to, yes, 10.
Still, not everyone is utterly convinced of the drastic insect decline narrative. Manu Saunders, an entomologist and ecologist doing postdoctoral studies at the University of New England in Australia, isn’t ready to put a number on the crisis or describe it as “global,” saying we just don’t know enough yet. “There is no verified evidence that global insect populations are in decline, based on the collective scientific knowledge of insect ecology generally and insect population studies.” Saunders says that, at this point, she’s less concerned about insect decline than about our “limited understanding of what these changes mean, because we know so little about most insect species.”
That being said, all but one of the scientists interviewed for this story believe that, limited as it is, current research suggests something, or more than one thing, is decimating insects, potentially across most insect families and potentially around the world. A paper in Science in 2014, looking at declines across all animal species, concluded that invertebrate populations, which include insects, had fallen by 45 percent over 40 years. This is less than the 2.5 percent annual drop listed in the meta-review, but still staggering and shocking.
“Estimates alone do not tell us the entire story. They are like movie trailers — you get the gist but you have to watch the entire movie to understand what is going on,” says Danielle Salcido, a University of Nevada graduate student who is studying neotropical insects. Put simply, while global estimates are informative, they don’t give us the specifics of which species’ populations are falling, rising or stable; in other words, the meta-research just can’t capture the full complexity of nature.
Why we can’t wait
Given the dearth of data on insect families (there has been, for example, almost no research into the abundance of ants), much of today’s unfolding crisis remains shrouded in mystery. But this is what we do know: something may be seriously, perhaps catastrophically, amiss in the largely unseen world inhabited by insects. And that’s enough, entomologists say, for us to act now.
“I think getting caught in the debate over how legit these studies are, how serious the situation is, is potentially just wasting important time,” Trautwein says.
“There’s no harm done in taking these studies seriously, and assuming we’re at a point where we’ve been warned that we need to be a lot more careful and contemplative about how to move forward.”
For Martins, whose Kenyan bush meals are lonelier now, the concern isn’t so much for the lack of his little uninvited guests, but for humanity.
“To a large extent, we’re still living in the age of insects,” he says. “If we continue messing things up, the insects will have the last laugh.”