What Are the 200 Million Termite Mounds in Brazil?

In northeastern Brazil, roughly 200 million termite mounds stretch across 89,000 square miles of caatinga scrubland — an area the size of Great Britain — spaced with uncanny regularity and standing up to 8 feet tall. Published in Current Biology in 2018, this is the largest known structure ever built by a single insect species on Earth.

Not Nests — Waste Heaps

The most counterintuitive fact about these mounds is what they actually are. They are not colonies. They are not homes. Each cone-shaped pile is a waste heap — excavated soil pushed upward by a single termite species, Syntermes dirus, as it carved an enormous underground tunnel network beneath the caatinga floor. The termites live below. The mounds are simply the debris.

This distinction matters enormously. It means the visible landscape — 200 million earthen cones scattered to the horizon — is just the byproduct of something far larger and more purposeful happening underground.

The Engineering Behind the Spacing

The mounds are evenly spaced, and that regularity is not accidental. The tunnel network below was built to fan out and cover the maximum possible ground without overlap. Each branch of the system needs equal access to the surface above it.

The reason comes down to timing. The caatinga is a semi-arid environment with a single, brief annual leaf-fall — one short window when food is abundant on the forest floor. Syntermes dirus evolved a solution: a hidden highway system radiating outward in every direction, so that when the leaf-fall arrives, every part of the network can reach it simultaneously. The even spacing of the mounds above is the surface signature of that underground logic.

Built Over Nearly 4,000 Years

Researchers used optically stimulated luminescence (OSL) dating to determine when the soil in the mounds was last exposed to sunlight — that is, when it was excavated. Some mounds dated to 3,820 years ago, placing their construction well before the founding of ancient Rome.

This is not a single construction event. The tunnel network expanded gradually across millennia, with new mounds forming as new tunnels were dug. The system self-organized without any central coordination — no queen issuing orders, no master plan. The even spacing emerged from the simple rule that each new tunnel grew where existing tunnels had not yet reached.

The Scale of Excavation

To quantify the work involved, researchers calculated the total volume of soil displaced. The figure is staggering: 2.4 cubic miles of earth — roughly equivalent to the soil volume of 4,000 Great Pyramids of Giza. Every grain was moved by an insect roughly the size of a rice grain.

The mounds themselves average 8 feet tall and 30 feet wide. Seen from satellite, the landscape they create is almost geometric — a natural structure so regular it initially looked artificial to researchers viewing aerial imagery.

Hidden in Plain Sight

Despite covering an area the size of Great Britain, this system was effectively unknown to science until researchers began analyzing satellite and Google Earth imagery of the region. The caatinga’s dense vegetation had concealed the mounds from casual observation for centuries. Local inhabitants knew of them, but no systematic scientific study had been conducted.

The 2018 Current Biology paper by Stephen Martin and colleagues brought the discovery to global attention — revealing that one of the largest biological construction projects in Earth’s history had been sitting quietly in plain sight, grain by grain, for nearly four thousand years.