Earth has around 20 quadrillion ants, study finds

Ants are small in size but not in number. There are about 20 quadrillion ants on Earth at any given time, a new study has estimated. There are 20,000 trillion individuals.

The estimate is two to 20 times higher than previous ones, according to the study, published in the journal Proceedings of the National Academy of Sciences on Monday (19).

“We were very surprised by the large number of ants we found,” Sabine S. Nooten, an insect ecologist and temporary principal investigator at the University of Würzburg in Germany, told CNN on Tuesday (20). Nooten was co-lead author of the study.

“We had virtually no expectations because the numbers that fluctuated beforehand in the scientific literature were basically educated guesses, and they had very little empirical data to work with,” she added. “And so this is the novelty of our study because we synthesized data from many empirical studies.”

The earlier global estimate of between one quadrillion and ten quadrillion ants by biologists Bert Hölldobler and Edward O. Wilson assumed that they accounted for approximately 1% of the world’s estimated insect population of one quintillion individuals, according to the study.

However, the research team for this latest survey based the new estimate on observational evidence from an extensive dataset of globally distributed ant samples. The authors identified and evaluated 465 suitable studies, covering 1,306 sampling sites, covering all continents and major biomes where ants live.

Scientists can use the study’s comprehensive dataset, which spans 80 years, to predict what future communities or environments will look like, according to Nooten. For example, the team estimated the number of land ants, which densely populate tropical and subtropical regions such as South American forests, at about 3 quadrillion.

“We can already see changes over time in our dataset,” he told CNN co-author Patrick Schultheiss, principal investigator at the University of Würzburg. Schultheiss pointed out that changes in agriculture or the way forests have been harvested could have an impact on ant numbers.

“No one has ever assembled a dataset on ants on a global scale,” Schultheiss said. He added that while they knew from studies that ant numbers were very high in West African rainforests compared to Arctic regions, “we didn’t know what the picture is — how many numbers there were.”

The estimated abundance of ants exceeds the combined biomass—that is, the total mass—of wild birds and mammals and amounts to about 20% of human biomass, according to the study.

“A surprisingly common question I’m asked is ‘How many ants are there on Earth?’ and while there are some estimates, none of the numbers used seem robust,” Adam Hart, a professor of science communication at the University of Gloucestershire, England, told CNN .

Hart, who is also vice president of the UK’s Royal Entomological Society, was not involved in the study.

“This new study, based on nearly 500 studies worldwide, gives us the best answer to this tricky question. What’s surprising is not just the total number, but the proportion of biomass that ants represent — one-fifth of the biomass of all humans. It really highlights how important ants really are,” he added.

A ‘conservative’ figure

The estimated overall number is almost unimaginably large, but the study’s authors said it’s “conservative.” This is because they weren’t able to gather all the data they wanted to include.

For example, many ants live underground, but there were no studies available that could provide numbers on how many, Schultheiss said.

There are ants in the far north and far south, such as the sub-Antarctic region, but there have not been enough studies of ants in these areas to make a mathematical estimate.

Citizen scientists could fill in these gaps, according to Schultheiss, who said that non-scientists, even students, could contribute to the dataset in impactful ways simply by collecting litter from leaves, pulling out all the ants, and counting how many there are.

“We hope to inspire people, first and foremost, to respect nature, to enjoy nature, because it’s amazing what ants can do and at what scale. But, also, if they are willing to contribute to science with a very simple method, even very simple data can be of enormous value,” he added.