Earth contains at least 20 quadrillion ants and they weigh more than all land birds and mammals combined.

The developed social organization of ants allowed the colonization of almost all ecosystems and regions of the world, with the exception of the polar regions.

This astonishing spread of ants has led many naturalists to think about their exact numbers on Earth. But those were basically rough estimates. The authors of the new study say there have been no systematic, evidence-based estimates yet.

This study is based on an analysis of 489 studies of ant populations conducted by specialists around the world.

The studies cover all continents—except Antarctica—and major habitats, including forests, deserts, grasslands, and cities. The researchers used standardized methods for collecting and counting ants, such as dug pits that catch ants that pass over a period of time, and counting ants that live on the bottom among the leaves in a specific patch of soil.

Based on this analysis, the researchers came up with about 20 quadrillion ants, 20 million, 20 thousand million or 20 with 15 zeros. This number is 2 to 20 times higher than previous estimates, but the researchers themselves call it ‘conservative’, so on the low side out of caution. More on that later.

These previous estimates took a top-down approach, assuming that ants make up about one percent of the estimated global insect population. The researchers say 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.