The sophisticated social organization of ants has allowed them to colonize almost all ecosystems and regions in the world, with the exception of the polar regions.
That astonishing ubiquity of ants has prompted many naturalists to ponder their exact numbers on Earth. But those were essentially rough estimates. There have been no systematic, evidence-based estimates until now, the authors of the new study say.
This study is based on an analysis of 489 studies of ant populations conducted worldwide by specialists.
The studies span all continents – with the exception of Antarctica – and key habitats, including forests, deserts, grasslands and cities. The researchers used standardized methods to collect and count ants, such as dug-in pits that catch the ants that pass by during a certain period of time and counting the ants that live on the bottom between the leaves in a demarcated patch of soil.
Based on that analysis, the researchers arrive at about 20 quadrillion ants, 20 million billion, 20 thousand million million or 20 with 15 zeros. That number is between 2 and 20 times higher than the earlier estimates, but the researchers themselves call it ‘conservative’, so on the low side for the sake of caution. More on that later.
Those earlier estimates took a top-down approach, assuming that ants make up about one percent of the estimated global insect population. The new study’s “bottom-up” estimate is more reliable because it uses data on ants collected directly in the field and makes fewer assumptions, the researchers say.