The Ant Biomass Paradox: How Earth's Tiniest Workers Match the Weight of All Humanity

The Numbers Behind the Comparison

An estimated 20 quadrillion ants — that is 20,000,000,000,000,000 individual insects — inhabit Earth at any given time. A 2022 study published in the Proceedings of the National Academy of Sciences, the most comprehensive ant census yet attempted, arrived at this figure by synthesizing data from more than 1,000 studies covering ant populations across every continent except Antarctica.

Individual ants weigh between 1 and 5 milligrams depending on species, with worker ants at the smaller end. Averaging across species and castes, the total dry carbon mass of Earth's ant population works out to approximately 12 million tonnes of carbon — roughly equivalent to about 20% of the total human biomass when measured in the same units. In terms of wet weight (the measure most people think of intuitively), the ant total approaches but does not quite equal the human total, making the comparison an approximation rather than a precise equivalence. The rough equality is genuine and meaningful — even if the exact ratio shifts slightly depending on methodology.

Why Ants Are So Extraordinarily Numerous

Ants have been evolving for approximately 140 million years. They appeared in the Cretaceous period and survived the mass extinction event 66 million years ago that wiped out non-avian dinosaurs. In the time since, they have colonized essentially every terrestrial habitat on Earth except Antarctica, achieving densities in tropical forests that can exceed 8 million individuals per hectare.

Their success comes from a combination of traits: eusocial colony structure that coordinates labor efficiently, chemical communication via pheromones that allows individuals to act coherently as a collective, dietary flexibility that permits exploitation of enormously varied food sources, and the ability to thrive in soil environments that are largely inaccessible to larger predators. Some species farm fungi. Others herd aphids for their secretions. Still others conduct coordinated military raids on other insect colonies. The behavioral repertoire of ants, taken across 20,000 known species, covers nearly every ecological niche available to small ground-dwelling arthropods.

What Biomass Comparisons Reveal About the Living World

The ant-human weight comparison is part of a broader scientific effort to understand how Earth's biomass is actually distributed. A landmark 2018 study by Bar-On, Phillips, and Milo mapped the total carbon mass of all life on Earth and produced findings that challenge most people's intuitions about the distribution of life. Plants account for about 82% of all living carbon mass. Bacteria account for roughly 13%. All animals combined represent less than 0.5% of Earth's biomass. And within that animal fraction, marine fish outweigh humans, and livestock outweigh wild land mammals.

Insects collectively represent a substantial fraction of animal biomass, with ants among the most significant contributors. Termites, often compared to ants in discussions of social insect biomass, add another comparable figure. The combined biomass of social insects appears to substantially exceed that of all vertebrate animals on land.

Ecological Importance Far Exceeds Their Size

The reasons scientists study ant biomass go beyond curiosity. Ants perform enormous ecological services: they aerate soil through their tunneling activity, distribute seeds for hundreds of plant species, decompose organic material, and regulate populations of other insects. Some tropical forests depend on ant activity for soil nutrient cycling to such a degree that significant reductions in ant populations measurably affect plant growth. Leafcutter ants in Central and South America are among the planet's most significant herbivores, harvesting an estimated 15% of all plant material in some tropical forests.

The biomass comparison with humans is striking because it reframes humanity's place in the living world. Eight billion people, with all of our cities, agriculture, technology, and dramatic planetary footprint, weigh about the same as the insects going quietly about their work beneath our feet. Mass is not influence — humans have altered the planet in ways that no ant colony has managed. But in terms of the raw weight of living matter, the comparison is a useful corrective to any assumption that size and visibility determine significance.