For every person alive on Earth, roughly 2.5 million ants are going about their business, tunneling through soil, dispersing seeds, and recycling organic matter. That ratio comes from a global census that tallied approximately 20 quadrillion individual ants, a number so large it translates to about 12 million tons of carbon in ant biomass alone. The sheer weight of these insects exceeds that of all wild birds and mammals combined, a finding that forces a reconsideration of which animals truly dominate the planet’s ecosystems.
Why a 20-quadrillion-ant planet demands attention now
The estimate did not emerge from a single field survey. It drew on an analysis of 489 studies spanning every continent where ants are found. Researchers compiled ground-level sampling data, then modeled total abundance across habitats and latitudes to arrive at the 20,000,000,000,000,000 figure. That synthesis, published in Proceedings of the National Academy of Sciences (DOI 10.1073/pnas.2201550119), represents the most data-intensive attempt yet to pin down a global ant count.
Independent coverage of the work underscored the scale of the finding, with one report noting that the 20-quadrillion estimate implies ants alone make up a significant fraction of global insect biomass. Another summary emphasized how the study shows that ants on Earth collectively outweigh many larger, more charismatic groups of animals that typically dominate conservation debates.
The ecological stakes behind this number are direct. Ants aerate soil by excavating billions of tiny tunnels, improving water infiltration and root growth for crops. They disperse seeds for thousands of plant species and serve as a food source for birds, lizards, and other wildlife. When ant populations decline in a given area, those services shrink. The concern is straightforward: regions where pesticide use is climbing fastest may be the same regions where ant-driven soil turnover matters most for agriculture. If that overlap holds, rising chemical application rates could erode the very soil health that farmers depend on, and the losses would compound over relatively short timescales.
That hypothesis has not been formally tested at a global scale, partly because the data needed to track ant population trends over time is still thin. The 489-study compilation provides a snapshot, not a time series. Tracking whether ant numbers are rising or falling in high-pesticide zones will require repeated surveys in the same locations, work that has barely begun in many tropical and subtropical agricultural belts. Until those longitudinal datasets exist, scientists can only infer potential risks from broader patterns in land use, climate, and insect decline.
How 489 studies produced 12 million tons of carbon
The research team aggregated field counts from pitfall traps, leaf-litter extractions, and soil cores collected across decades of independent studies. By standardizing those counts and scaling them against mapped habitat areas, they arrived at the 20 quadrillion estimate published in PNAS. Converting raw abundance into biomass yielded approximately 12 million tons of carbon, a figure that puts ants in the same weight class as humanity’s most abundant livestock.
The biomass comparison is striking because wild birds and mammals, from sparrows to elephants, collectively weigh less than the planet’s ant population. That disparity reflects ants’ extraordinary density at ground level. A single colony can contain millions of workers, and colonies blanket nearly every terrestrial habitat from boreal forests to tropical rainforests to urban sidewalks. The research confirmed that tropical regions harbor the highest concentrations, though temperate and arid zones contribute meaningful numbers as well.
Translating scattered field measurements into a global map required several modeling steps. The team first grouped sampling sites by habitat type and climate zone, then calculated average ant densities for each category. Those averages were multiplied by the total area of each habitat worldwide. Finally, the authors combined aboveground and leaf-litter counts with limited data from deeper soil layers to estimate the full vertical distribution of ants in the ground. Each layer of extrapolation introduced uncertainty, but it also allowed the researchers to move beyond the heavily studied forests and grasslands of Europe and North America.
A separate commentary piece (DOI 10.1073/pnas.2214825119), indexed in the National Library of Medicine, evaluated the methods behind the estimate and flagged the same limitation the original authors acknowledged: sampling coverage remains uneven. Africa and central Asia contributed far fewer field studies than the Americas, Europe, or Australia. The 2.5-million-per-human ratio therefore rests partly on modeled extrapolations for undersampled regions, and the true global number could be higher or lower depending on how well those models capture real ant densities in data-sparse areas.
Gaps in tropical and arid sampling leave key questions open
The most significant unresolved problem is geographic bias. Tropical forests, which the study identifies as ant-density hotspots, are also among the least systematically sampled habitats. If actual densities in those forests differ meaningfully from the modeled values, the global total shifts by trillions of individuals. The same uncertainty applies to arid and semi-arid landscapes across the Sahel, the Arabian Peninsula, and the steppes of central Asia, where ant ecology research has been sparse.
A second open question is temporal direction. The 489-study compilation tells us how many ants exist at a point in time but says almost nothing about whether that number is growing or shrinking. Insect decline research over the past decade has documented sharp drops in flying insect biomass in parts of Europe, yet ants, which spend most of their lives underground, have not been tracked with the same rigor. Without repeated censuses in the same locations, claims about ant population trends remain speculative.
Climate change adds another layer of uncertainty. Ant species are finely tuned to temperature and moisture, and shifts in rainfall patterns or heat extremes could reconfigure community composition in ways that either amplify or erode their ecosystem roles. Some species may expand into new regions as conditions warm, while others retreat or disappear locally. Whether those changes maintain, increase, or diminish total ant biomass is an open empirical question.
The practical consequence for anyone who grows food or manages land is this: ants perform billions of dollars’ worth of ecosystem labor, from soil mixing to pest control, and we still lack the monitoring infrastructure to know whether that labor force is stable. The next development to watch is whether research groups begin deploying standardized, repeatable ant surveys in the tropical and arid regions where current data is weakest. Building that network of long-term plots and harmonized sampling methods would transform a one-time global headcount into an early-warning system for the planet’s most numerous ground-dwelling animals.
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*This article was researched with the help of AI, with human editors creating the final content.
