The world is home to at least 20 million billion ants

At least 20 million billion ants exist on Earth, according to a new study providing a probably still largely underestimated estimate of the global population of these insects, key to their ecosystem.

Counting how many ants inhabit the globe is important in order to be able to measure the consequences that changes to their habitat (including climate change) can have. Ants play a significant role wherever they are present, serving both as a means of dispersal for plant seeds, as hosts for certain organisms, and as predators or prey for other animals.

Some studies had already attempted a count based on an estimate of the overall insect population and had resulted in a much lower number of ants. For this new attempt, published Monday in the scientific journal "Proceedings of the National Academy of Sciences" (PNAS), the researchers analyzed the results of 465 studies that measured locally, in the field, the number of ants.

These hundreds of studies have used two standardized techniques: the setting of traps capturing individuals passing by for a certain period of time, or the analysis of the number of ants present on a given plot of foliage on the ground.

20% of human biomass

The total biomass of ants on Earth (measured in dry matter) is thus estimated at 12 million tonnes. This is more than the biomass of wild birds and mammals combined, and it is 20% of that of humans.

While surveys have been carried out on all continents, some large regions presented very little or no data, particularly in Central Africa and Central Asia. That's why "the true abundance of ants is likely considerably higher," the study warns. “It is of the utmost importance that these gaps are filled in order to provide the complete picture.”

According to the study, there are more than 15,700 species or subspecies of ants, and likely many more yet to be described. Amazingly, they are present everywhere on the planet. But nearly two-thirds of ants are found in just two types of ecosystems: tropical forests and savannahs, the work concludes.

In the future, the researchers plan to study the environmental factors influencing the density of ant populations.