Spoiler: their number greatly exceeds the billion scale.
It’s a question that many of us have already asked ourselves when crossing paths with a colony of well-organized insects: how many ants are there on Earth?
At first glance, this question might seem futile; you don’t need to be a great scientist to realize that it is simply impossible to list them one by one. We could therefore be tempted to close the file once and for all. But this funny question is much more interesting than one might think at first glance, and serious researchers are also looking into it.
Recently, a new international team of researchers based at Julius Maximilian University, Germany, attempted to come up with the most accurate estimate yet of the number of Formicidae on a planetary scale. Of course, they didn’t start gutting anthills by the dozen; instead, they conducted what is called a meta-analysis.
A large-scale meta-analysis
This is a somewhat special category of study, since it is not based on an experimental protocol established by the authors to verify their hypothesis. It is rather a question of harvesting all the serious scientific literature that exists around a specific subject. For the most solid meta-analyses, specialists often rely on dozens, even hundreds of studies that are relatively independent of each other.
Once this documentation work has been completed, researchers can then extract all the data that interests them, then cross-check and compare them using advanced statistical tools to draw conclusions on a larger scale.
In this specific case, the authors went through no less than 489 different studies that document the density of certain ant populations in given areas. They have a very important point in common: all these works are based on a standardized census method, which means that the methodology is very similar from one paper to another.
They were able to integrate all this data into a huge statistical model. The objective: to bring out clear correlations between the density of the ant population and lots of external factors such as the climate of the area concerned, for example.
This is significant progress, as until now, work of this kind has typically relied on measurements drawn from one or two isolated geographic areas. In essence, these were therefore only “educated guesses”, according to Patrick Schultheiss, co-lead author of the study.
At least 20 million billion ants on Earth!
From these elements, all they had to do was extrapolate to the scale of the whole planet to arrive at an estimate of the world population of ants. They were thus able to offer the best estimate of the total population of ants to date: for them, our planet was home to at least… 20,000,000,000,000,000 ants, or 20 billion, or even 20 million billion of these insects.
A number that makes you dizzy; this represents approximately 2.5 million ants for each of the (almost) 8 billion humans who inhabit the Earth. And the observation is even more impressive when we think in terms of biomass. Based on this estimate, the ant population represents about 12 million tons of carbon. Excluding humans, that’s more than all birds and land mammals combined!
However, it is important to remember that this estimate remains relatively vague, although it is the first study of its kind to present such a robust methodology. Because even if meta-analyses of this kind can bring out clear trends, they also suffer from a sometimes prohibitive defect: the data must be as precise and exhaustive as possible.
However, in the real world, it is physically impossible to collect perfectly representative data sets. This means that the quality and density of the readings will necessarily be heterogeneous. Result: there are still considerable gray areas in our knowledge of the 15,700 documented species of ants.
For example, if European ants are extremely well known, the same cannot be said of African or North Asian species. This also applies to certain ecological niches.
These include the canopy of tropical jungles or underground passages, which are often difficult to access for researchers; these areas are therefore much less studied than the soil of European forests, for example, and this necessarily has considerable consequences on the study of the species that reside there. For all these reasons, the real population of ants could still be much higher than the announced figure!
Ants, major players in the environment
Ultimately, despite these approximations, this work remains very important. Indeed, monitoring the global ant population has deeper implications than meets the eye. It’s not all about curiosity or conservation efforts. These insects are immensely important in the overall dynamics of a host of ecosystems, and this information allows us to appreciate their status as ecological hub.
It is often said that the survival of humanity is intimately linked to that of bees, in particular thanks to their role in the pollination of plants. But ants also play a determining role in their respective ecological niches. They are, for example, major players in soil mixing; they promote the transport of water, oxygen and nutrients essential to the growth of plants and micro-organisms.
They are also one of the pillars of the global food chain; ants are the basis of the diet of very many species which would be instantly threatened with extinction if the ants were to disappear. Studying the population of ants therefore makes it possible to better control the complex dynamics that animate this great ecological mille-feuille.
” With this study, we provide a basis for the global distribution of ant number and biomass. In the future, we can repeat these studies in the same places, with the same methods, to see what has changed. “, explains Sabine Nooten, second co-author of the paper.