It’s the ants’ world, and we’re just visiting.
In a paper released Monday by the Proceedings of the National Academy of Sciences, a group of scientists from the University of Hong Kong analyzed 489 studies and concluded that the total mass of ants on Earth weighs in at about 12 megatons of dry carbon, a standard way of measuring animals’ biomass.
Put another way: If all the ants were plucked from the ground and put on a scale, they would outweigh all the wild birds and mammals put together. For every person, there are about 2.5 million ants.
“It’s unimaginable,” Patrick Schultheiss, a lead author on the study who is now a researcher at the University of Würzburg in Germany, said in a Zoom interview. “We simply cannot imagine 20 quadrillion ants in one pile, for example. It just doesn’t work.”
Counting all those insects — or at least enough of them to come up with a sound estimate — involved combining data from “thousands of authors in many different countries” over the span of a century, Schultheiss added.
To tally insects as abundant as ants, there are two ways to do it: Get down on the ground to sample leaf litter — or set tiny pitfall traps (often just a plastic cup) and wait for the ants to slip in. Researchers have gotten their boots dirty with surveys in nearly every corner of the world, though some spots in Africa and Asia lack data.
“It’s a truly global effort that goes into these numbers,” Schultheiss said.
Ants, like humans, have marched across virtually every continent and all sorts of habitats. Ground-dwelling ants are most abundant in tropical and subtropical regions, according to the research team, but they can be found nearly everywhere except the coldest parts of the planet.
Or as renowned author and myrmecologist (that means ant scientist) E.O. Wilson once put it: “No matter where I go — except possibly Antarctica or the high Arctic, and I don’t go there because there are no ants there — no matter how different the human culture, no matter how different the natural environment, there are the ants.”
The world, indeed, may be better off with all these ants. By tunneling, they aerate soil and drag seeds underground to sprout. They serve as a source of food for untold arthropods, birds and mammals. While carpenter ants are pesky to homeowners, forests would be stacked to the brim with dead wood without the decomposing power of wood-destroying insects.
Entomologists are seeing troubling declines in insect populations beyond ants in Germany, Puerto Rico and elsewhere. Habitat destruction, pesticides and climate change contribute to this potential-but-still-debated “bugpocalypse.” Over 40 percent of insect species may go extinct, according to a 2019 study, with butterflies and beetles facing the greatest threat.
Scientists aren’t sure whether ants’ numbers are falling as well. “To be honest,” Schultheiss said, “we have no idea.”
That’s the next research question the team wants to answer. “We did not yet attempt to show this temporal shift in ant abundance,” Sabine Nooten, an insect ecologist and co-lead author of the study, said by Zoom. “That would be something that would come next.”
For decades, scientists have gazed into ant farms in labs to test theories on animal behavior. The ant scientist Wilson, who died last year, used his insights into ants to help explain the genetic basis for cooperation among animals and to underscore the sheer biodiversity of life worth preserving.
In the 1990s, he ventured a rough guess at Earth’s ant population with fellow biologist Bert Hölldobler. Their estimate was about 10 quadrillion — within the same order of magnitude as the recent and more rigorous estimate published Monday.
“In the case of E.O. Wilson, he was simply a very smart man,” Schultheiss said. “He knew an awful lot about ants and had a gut feeling, basically.”
