For the first time, scientists have estimated how many ants live on the Earth's surface based on 465 previous studies.

The estimated total number of 20 quadrillion is around 2.5 million times higher than the number of humans - and is associated with various uncertainties, according to the research team in its study in the specialist journal "PNAS" a fluctuation range of plus or minus 5 quadrillion ants.

However, the actual number could be even higher, as no valid estimates are available for ants living underground.

For other habitats, the team led by researchers from the University of Hong Kong evaluated the available regional censuses and extrapolated them according to the total area of ​​the different habitat types.

More biomass than that of wild birds and mammals combined

Hinnerk Feldwisch-Drentrup

Editor in the department "Nature and Science".

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So far there have only been much rougher estimates, which were extrapolated to the global landmass of the earth on the basis of small investigations of areas in England, for example, says zoologist Patrick Schultheiss, who has since moved from the Asian metropolis to the University of Würzburg.

This estimate resulted in a number of a few quadrillion ants - which is at least similar to the current result in terms of magnitude.

"We had no idea what the number could be - everything was surprising," he says.

The estimated biomass of ants is greater than that of wild birds and mammals combined, and is equivalent to around 20 percent of the biomass of all humans.

"Our first concern was to find out whether the density of ants is the same in different regions," explains Schultheiss, explaining the motivation of the team - this allows conclusions to be drawn about the importance and integration of insects in different ecosystems.

A good 60 percent of the ants that live above ground live in tropical rain forests;

the number of ants per area is higher there than in steppes, for example, but lower in park landscapes.

It was already known that the number of ant species in the tropics is higher, says Schultheiss.

Still large gaps in knowledge

It is also important that with the review the team has now determined for which regions of the world there are studies on the ant populations that occur in each case.

There are many surveys for southern Africa, but not for more northern regions of the continent.

In total, the team was able to draw on around 1,300 local censuses worldwide.

"We hope that the study will encourage people to collect data," says Schultheiss.

Datasets on regional occurrences are enormously important and allow conclusions to be drawn about what ants can do.

"It is of utmost importance to fill the remaining knowledge gaps in order to obtain a comprehensive picture of insect diversity - and a global understanding of the worldwide patterns of biodiversity and their drivers," the team writes in their article.

"As a global community, we should focus our efforts on the regions, habitats, and regional communities we know least about—while we still can."