There are 20 quadrillion ants on the planet, and they weigh more than all wild mammals and birds combined

If you've ever wondered how many ants there are in the world.
Ameya Paleja

There are 20 quadrillion ants on the planet, according to a new estimate made by researchers at the Julius Maximilian University of Würzburg in Germany, New Scientist has reported.

Prior to this, estimates of their numbers were "essentially educated guesses" from scientists. So, the researchers put together data from 489 studies about ant population densities in various parts of the world. The numbers they got were then extrapolated to the size of the globe, and that's how the number 20,000,000,000,000,000, or 20 quadrillions, was reached.

The significance of ants

Ants are found in abundance in tropical and subtropical regions, but their numbers vary substantially across habitats. Scientists may be impressed by their engineering skills but need to know their numbers to determine their role in ecosystems.

We have over 15,700 known species of ants, which have been found to have roles such as dispersing seeds, increasing nutrient availability, as well as the role of food in the various ecosystems. Yet reliable data has been missing in this domain, and the researchers at Julius Maximilian University set about to collate it.

The 489 studies they used in their research consisted of ant numbers from all continents on the planet, major biomes, and habitats. According to their conservative estimates, there are about three quadrillions (3 × 1015) of ground-dwelling ants on the planet, while the total number is expected to be 20 quadrillions.

Not the complete estimate though

The total biomass of this population is estimated to be 12 megatons. This is much higher than the combined biomass of birds and mammals in the wild, which sums up to nine megatons, New Scientist said in its report. At 60 megatons, the human biomass is five times larger.

The study also found that forest areas had the highest density of ants while ground-foraging ants were the highest in number in arid regions. Yet, the estimates do not provide us with the complete picture. For instance, the estimates are only based on ant numbers on the ground and do not include those that are underground or harbored in trees.

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Additionally, there was limited data available about ant populations from Africa and north Asia, researcher Patrick Schultheiss told New Scientist. This means that there are still major gaps in our understanding of the ant populations and their numbers.

Given their role in various ecosystems, the estimation of ant numbers will also serve as a baseline for their distribution. In the future, researchers can use the same methods in the same places to determine what has changed in the ant biomass and study its impact.

The researcher's findings were published this week in the Proceedings of the National Academy of Sciences.

Abstract

Knowledge on the distribution and abundance of organisms is fundamental to understanding their roles within ecosystems and their ecological importance for other taxa. Such knowledge is currently lacking for insects, which have long been regarded as the “little things that run the world.” Even for ubiquitous insects, such as ants, which are of tremendous ecological significance, there is currently neither a reliable estimate of their total number on Earth nor of their abundance in particular biomes or habitats. We compile data on ground-dwelling and arboreal ants to obtain an empirical estimate of global ant abundance. Our analysis is based on 489 studies, spanning all continents, major biomes, and habitats. We conservatively estimate total abundance of ground-dwelling ants at over 3 × 1015 and estimate the number of all ants on Earth to be almost 20 × 1015 individuals. The latter corresponds to a biomass of ∼12 megatons of dry carbon. This exceeds the combined biomass of wild birds and mammals and is equivalent to ∼20% of human biomass. Abundances of ground-dwelling ants are strongly concentrated in tropical and subtropical regions but vary substantially across habitats. The density of leaf-litter ants is highest in forests, while the numbers of actively ground-foraging ants are highest in arid regions. This study highlights the central role ants play in terrestrial ecosystems but also major ecological and geographic gaps in our current knowledge. Our results provide a crucial baseline for exploring environmental drivers of ant-abundance patterns and for tracking the responses of insects to environmental change.

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