In a paper published 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 around 12 megatons of dry carbon.
In other words: if all the ants were pulled out of 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,” said Patrick Schultheiss, one of the study’s lead authors who is now a researcher at the University of Würzburg in Germany, in a Zoom interview. “We just can’t imagine 20 quadrillion ants in a single pile, for example. It just doesn’t work.
Counting all of these insects — or at least enough of them to come up with a solid estimate — involved combining data from “thousands of authors in many different countries” over a period of a century, Schultheiss added.
To count insects as abundant as ants, there are two ways to go: get down on the ground to sample the leaf litter – or set up tiny pitfall traps (often just a plastic cup) and wait for the ants to creep in on the inside. Researchers have gotten their boots dirty with surveys in almost every corner of the world, although some places in Africa and Asia are missing data.
“It’s a truly global effort that goes into those numbers,” Schultheiss said.
Ants, like humans, have crossed virtually every continent and every kind of habitat. According to the research team, ground ants are most abundant in tropical and subtropical regions, but they can be found almost anywhere except the coldest parts of the planet.
Or as EO Wilson, renowned author and myrmecologist (i.e. ant scientist) once said: “It doesn’t matter where I go – except maybe Antarctica or the High Arctic, and I’m not going there because there are no ants there – no matter how different from human culture, no matter how different the natural environment is, there are ants.
The world, indeed, can be better off with all these ants. By digging tunnels, they aerate the soil and drive the seeds underground to germinate. They serve as a food source for countless arthropods, birds and mammals. While carpenter ants are a nuisance to homeowners, forests would be filled to the brim with dead wood if not for the decaying 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. According to a 2019 study, more than 40% of insect species could disappear, with butterflies and beetles being the most threatened.
Scientists do not know if the number of ants is also decreasing. “To be honest,” Schultheiss said, “we have no idea.”
This is the next research question the team wants to answer. “We haven’t attempted to show this temporal change in ant abundance yet,” Sabine Nooten, insect ecologist and co-lead author of the study, told Zoom. “That would be something that would come next.”
For decades, scientists have observed ant farms in laboratories to test theories about animal behavior. Ant scientist Wilson, who died last year, used his knowledge of ants to help explain the genetic basis of cooperation between animals and to highlight the biodiversity of life worth preserving.
In the 1990s, he attempted a rough estimate of Earth’s ant population with fellow biologist Bert Hölldobler. Their estimate was around 10 quadrillion – in the same order of magnitude as the recent, more rigorous estimate published on Monday.
“In EO Wilson’s case, he was just a very smart man,” Schultheiss said. “He knew an awful lot about ants and had a gut feeling, basically.”
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