Tom Wassmer is crouched down in a pasture, staring very intently at some cow manure.
Wassmer is pointing at a nondescript dung beetle, no bigger than a grain of rice, with a shiny black head and a matte brown body. Without the beetle, Wassmer said dung could sit on the ground surface of this Michigan farm for years.
“It would pile up,” said Wassmer, a biology professor at Siena Heights University. “You would probably see no grass anymore.”
He explains how dung beetles break up the manure and take small bits underground, turning the useless manure into accessible nutrients. These insects offer a valuable – if unrecognized – service that improves soil quality, prevents diseases and saves the U.S. cattle industry an estimated $380 million a year.
But Wassmer said he’s concerned to see how vulnerable dung beetles are to threats.
“We know that the soils are becoming more and more exhausted and need more and more fertilizer,” Wassmer said. “And you know, the insect decline story is definitely including dung beetles.”
Warnings of drastic insect losses
According to a 2019 study in the journal “Biological Conservation,” 40% of insect species are threatened by extinction and fading from places, even where they were thought to be abundant. The study warns that insects could be declining at rates 8 times faster than mammals, birds and reptiles.
Reports detailing staggering declines have caught the attention of the National Academy of Sciences (NAS), which plans to launch a study on insect populations next year. The goal is to make sense of existing data and identify priority species and regions.
Robin Shoen, director of the NAS Board on Agriculture and Natural Resources, said different papers can highlight contradicting trends.
“Some say there are declines and some say there are not. And what do we make of that? Can we tease that apart?” she said.
Schoen said the study would help inform solutions that can slow or reverse losses. The NAS is still assembling a research team and working to secure $1 million in funding, but Schoen noted a sense of urgency in initial committee meetings.
“It is very important to understand what's happening,” Schoen said. “We need to get a handle on this sooner rather than later.”
If all goes according to plan, Shoen said the 18-month study would be completed in 2026.
Tracking insects isn’t easy
There are more than a million known species of insects that make up around 80% of all animal life. If that’s not already an overwhelming number, entomologists estimate there may be up to 10 million insect species that haven’t even been discovered.
“They’re so numerous, and they’re so diverse,” said Christie Bahlai, a computational ecologist at Kent State University. “So, when you're measuring one facet of the insect community, you're not measuring so many other facets.”
Bahlai said the metrics used to quantify population changes are extra tricky with insects — whether researchers are counting individuals or measuring biomass in their samples.
“Percent decline kind of implies a stable population, and insects are really prone to boom and bust,” Bahlai said. “What I tend to do is use sort of a long-time average, but you can also critique that, too, since the range of the (peaks and troughs) matters.”
Wassmer said a lack of systematic data makes it difficult to draw conclusions. He’s part of a research workgroup representing around 80 universities across North America that are committed to using and sharing consistent data on insect populations from their respective regions.
“We don't have the primary data to show the decline, but we can be pretty sure when they don't have enough habitat and food, then that means they are on the decline,” Wassmer said.
While the estimated rates of decline can vary across studies, many entomologists say the drivers are obvious — and extensive. Climate change, habitat loss, light pollution and the widespread use of pesticides have made much of our environment unwelcoming to insects.
Looking beyond “pests”
As an insect diagnostician, Zach Schumm fields a lot of calls about insects, mostly from farmers, gardeners and homeowners looking to get rid of them.
“The attitude towards a lot of insects is, ‘Here's this insect I found, how do I exterminate it?’ Things of that nature,” said Schumm, who is with the Iowa State University Plant and Insect Diagnostic Clinic.
His go-to recommendation is “tolerance,” but if it’s not an option, Schumm said he’ll suggest strategies like spraying plants with water or rotating crops — with pesticides used as a last resort.
“There's a very small number of insects out there that are actually problematic for crops, households and home gardens,” Schumm said. “A lot of things are either beneficial. There's also many that are just neutral, where they're not really doing any harm.”
Schumm said the “pest” status insects automatically get isn’t fair to the hundreds of thousands of diverse species, many of which perform roles we rely on.
At the bottom of the food chain, insects feed birds and fish. Predatory insects like wasps and lady beetles eat species that can be destructive to crops. And while it can’t be overstated how important bees are for their pollination services, flies are also pollinators that support the production of foods like mangoes, avocados and chocolate.
“They're kind of like the foundational organisms on the planet,” Schumm said. “Without insects, same as if I said, without soil and microorganisms, humans don't really exist in the long-run.”
Declines aren’t universal
Invasive species like the spotted lanternfly and emerald ash borer have made headlines this past year for expanding their range. Tick numbers and cases of lyme disease are increasing across the upper Midwest. Insects that are better adapted to living alongside humans like cockroaches and houseflies are also faring well.
These trends can be attributed to some of the same factors that are driving declines and biodiversity losses, but it’s not all bad news.
Bahlai said insects can be “remarkably resilient” when they have the necessary resources. Movements around pollinator gardens and “No Mow May” are gaining traction, and they can have measurable impacts on native, beneficial species like the monarch butterfly.
“We see short-term recoveries in monarch populations when the conditions are good,” Bahlai said. “When people plant native plants in their gardens, we can have thriving populations of bees on these little islands within the suburbs.”
Agricultural practices like insect refuges and integrated pest management show promise in boosting insect populations.
Research from Michigan State University found that native wildflower plantings between blueberry fields increased the abundance of wild bees and the berry yield. Prairie strips in Iowa have been shown to support insect biodiversity in rural areas, as well as improving water and soil quality.
“We can protect biodiversity and nature better when we have a personal relationship to the land, and that calls for small family farms rather than these big factory farms,” Wassmer said, referencing how intensive agriculture is the main driver behind insect habitat loss.
Rebecca Deline said she didn’t think much about dung beetles before Wassmer approached her to study them on her 1,630-acre farm.
Deline raises cattle and grows corn, hay and soybeans. When it comes to making decisions about insects, Deline said she simply considers the “economic threshold.”
“Is it worth it to get rid of them, and are they really harmful?” Deline said. “Or are they beneficial to you? It depends on what the insect is. Does it cost more to get rid of them or does it cost more just to let them go?”
Deline has to make tough calls sometimes, but she’s never viewed insects as pests.
“Everything has a purpose,” Deline said. “Without them, we would be lost.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.
Audio extra: the “windshield phenomenon”
WCMU Public Radio asked listeners if they’ve noticed a decline of insects. Out of the 16 people that called in from across Michigan, nearly half mentioned the days when they would need to constantly pull over and clear their windshields of dead bugs.
These are just anecdotal observations, but the “windshield phenomenon” has been connected to the global decline of insects. Listen to their stories below:
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