Have you ever wondered how many ants there are in the world? The astonishing ubiquity of these insects has also led many naturalists to estimate their exact numbers on Earth, but systematic and empirical estimates have so far been lacking. A rigorous analysis allows us to see a little more clearly. So how many ants are there in this world? And what is the combined mass of all these insects?
Knowledge of the distribution and abundance of biodiversity is essential to understand the role of organisms within their ecosystems and, therefore, their ecological importance. These data are currently missing for insects, even for the most ubiquitous such as ants (15,700 species). However, these have considerable ecological importance.
In a new study, published in the Proceedings of the National Academy of Sciences, the researchers have relied on all currently available data to make a reliable estimate of the total number of ants on Earth, their biomass and their distribution. His meta-analysis is based on 489 studiescovering all continents, major biomes and habitats.
Based on the data analyzed, the researchers conservatively estimate that there are approximately twenty quadrillion (twenty million billion) of ants on Earth. This is twice the estimate of EO Wilson who, in 1994, estimated the number of ants by extrapolating data from south-east England. He notes that this new estimate does not account for colony members who do not leave their nests to forage, as well as areas such as boreal forests where data is sparse.
Biomass and distribution
Taking into account the diversity of ant weights, the authors also estimate that the dry carbon in these quadrillion small bodies amounts to approximately twelve megatons. For comparison, this equates to approximately 20% of human biomass.
Finally, on the distribution side, we learn that there are about six times as many tree ants as there are ground ants. In the latter, abundances are strongly concentrated in tropical and subtropical regions, but vary considerably across habitats. Leaf litter ant density, for example, is highest in forests, while the number of actively foraging ants on the ground is highest in arid regions.
For the authors, this new work highlights the central role of these insects in terrestrial ecosystems, but also important ecological and geographical gaps in our current knowledge. Ultimately, this new data could provide a baseline for tracking ant responses to environmental changes.