Have you ever wondered exactly how many ants live on Earth? Possibly not, but it’s definitely a question we’ve been asking ourselves.
Our research published today provides an approximate answer. We conservatively estimate that our planet is home to about 20 quadrillion ants. That’s 20 billion million, or in numerical form, 20,000,000,000,000,000 (20 with 15 zeros).
We further estimate that the world’s ants together make up about 12 million tons of dry carbon. This exceeds the mass of all the wild birds and wild mammals in the world combined. It is also equal to about a fifth of the total weight of humans.
Eminent biologist Edward O. Wilson once said that insects and other invertebrates are “the little things that run the world” — and he was right. Ants in particular are a crucial part of nature. Ants aerate the soil, disperse seeds, break down organic matter, create habitat for other animals and are an important part of the food chain.
Estimating ant numbers and masses provides an important basis for monitoring ant populations amid worrying environmental changes.
Counting the ants of the world
There are over 15,700 named species and subspecies of ants, and many others that have not yet been named by science. The high degree of social organization of ants has allowed them to colonize almost all ecosystems and regions around the world.
The astonishing ubiquity of ants has prompted many naturalists to ponder their exact numbers on Earth. But these were essentially educated guesses. Systematic, evidence-based estimates were lacking.
Our research included an analysis of 489 studies of ant populations conducted by fellow ant scientists from around the world. This included non-English literature, in languages such as Spanish, French, German, Russian, Mandarin, and Portuguese.
The survey covered all continents and major habitats, including forests, deserts, grasslands and cities. They used standardized methods for collecting and counting ants, such as traps and leaf litter samples. You can imagine that this is often tedious work.
Based on all this, we estimate that there are about 20 quadrillion ants on Earth. This figure, while conservative, is two to twenty times higher than previous estimates.
The previous figures used a “top-down” approach by assuming that ants make up about 1% of the world’s estimated insect population. In contrast, our bottom-up estimate is more reliable because it uses data on ants observed directly in the field and makes fewer assumptions.
Our next step was figuring out how much all these ants weigh. The mass of organisms is usually measured in terms of their carbon composition. We estimate that 20 quadrillion average-sized ants correspond to a dry weight or “biomass” of about 12 million tons of carbon.
This is more than the combined biomass of wild birds and mammals – and about 20% of the total human biomass.
Carbon makes up about half the dry weight of an ant. If the weight of other body elements were included, the total mass of the world’s ants would be even higher.
We also found that ants are unevenly distributed across the Earth’s surface. They vary six times between habitats and peaks generally in the tropics. This underlines the importance of tropical areas for maintaining healthy ant populations.
Ants were also particularly abundant in forests, and surprisingly in arid regions. But they are less common in man-made habitats.
Our findings come with a few caveats. For example, the sample locations in our data set are unevenly distributed across geographic regions. And the vast majority of samples were collected from the soil layer, which means we have very little information about ant numbers in trees or underground. This means that our findings are somewhat incomplete.
We all need ants
Ants also provide essential “ecosystem services” to humans. For example, a recent study found that ants may be more effective than pesticides in helping farmers produce food.
Ants have also developed close interactions with other organisms – and some species cannot survive without them.
For example, some birds rely on ants to flush out their prey. And thousands of plant species feed or house ants in exchange for protection or dispersal of their seeds. And many ants are predators and help control the populations of other insects.
Worryingly, insect numbers are declining worldwide due to threats such as habitat destruction and fragmentation, use of chemicals, invasive species and climate change.
But data on insect biodiversity is alarmingly scarce. We hope that our study provides a basis for further research to fill this gap.
It is in the interest of humanity to monitor ant populations. Counting ants isn’t difficult, and citizen scientists from around the world could help investigate how these important animals are doing at a time of major environmental change.
(Authors: Mark Wong, Forrest Fellow, The University of Western Australia; Benoit Guénard, associate professor, University of Hong Kong; François Brassard, PhD student, Charles Darwin University; Patrick Schultheiss, temporary principal investigator, Julius Maximilian University of Wurzburg; Runxi Wang, PhD student, University of Hong Kongand Sabine Nooten, temporary principal investigator, Julius Maximilian University of Wurzburg)
(Disclosure Statement: Mark Wong receives funding from the Forrest Research Foundation.
Benoit Guénard is an associate professor at the University of Hong Kong (HKU). This study was supported by funding from HKU, an Early Career Scheme from the Research Grant Council of Hong Kong (#ECS-27106417) and National Geographic.
Patrick Schultheiss is temporary principal investigator at the University of Würzburg in Germany. He is currently receiving funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – project no. 499479766. This study was further supported by a Postdoctoral Fellow Research Award from the Department of Ecology and Biodiversity at the University of Hong Kong.
Sabine Nooten receives funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) — project no. 445715161
François Brassard and Runxi Wang do not work for, consult, own shares in, or receive funding from, any company or organization that would benefit from this article, and have not disclosed any relevant affiliations outside of their academic appointments.)
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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