LiDAR Reveals a 3-Million-Person Civilization in the Amazon

Fly a laser over the Amazon canopy instead of a satellite camera, and an entirely different rainforest appears. Where old imagery showed 30 scattered structures in one patch of forest, the laser found 156. Multiply that gap across the wider region, and a picture emerges of a precolonial civilization that may have rivaled medieval Europe in population density.

A Civilization Hiding in Plain Sight

A research team led by Martti Pärssinen of the University of Helsinki and the Instituto Iberoamericano de Finlandia has used canopy-penetrating LiDAR to map thousands of geometric earthworks across southwestern Amazonia, revealing a precolonial society far larger and more organized than previously understood. The findings were published in the journal Nature.

The researchers focused on a cultural area they call the Aquiry civilization, named for the earthworks-and-geoglyphs tradition first documented in Brazil’s Acre state. Between 2001 and 2024, systematic study of satellite imagery and aerial photographs had already revealed nearly 1,300 earthworks across roughly 134,000 square kilometers of the region. The new LiDAR survey was designed to see what all that satellite imagery had missed.

Flying Lasers Over 4,430 Kilometers of Jungle

In 2024, the team flew airborne laser scanning surveys covering 4,430 kilometers of flight lines across the Brazilian states of Acre and Amazonas, using a long-range RIEGL LMS-Q780 II laser scanner mounted on a Seneca V aircraft. Unlike satellite or drone photography, this technology can penetrate small gaps in the forest canopy and generate a detailed terrain model of the ground beneath, exposing structures completely invisible from above.

The new data documented 432 earthworks, of which only 36 had been previously known. Combined with earlier satellite-based findings, researchers were now able to define the geographical extent of the Aquiry civilization with far greater precision than before, and to distinguish its structures from later, unrelated earthworks built centuries afterward.

Five Times More Than Satellites Ever Showed

The most striking result of the entire survey was a straightforward comparison. In one heavily studied block of deforested land, researchers had previously identified just 30 earthworks using satellite imagery from Google Earth, Bing, and ESRI. LiDAR scanning of the exact same area revealed 156, five times as many. That same multiplier held up consistently across every flight line in the study.

Extrapolated across the wider region, and accounting for how much of the dense forest canopy likely still hides additional structures from even LiDAR’s laser pulses, researchers estimate the true number of earthworks across the Aquiry civilization’s territory could be as high as 24,000 to 30,000, a dramatic jump from the roughly 200 structures known when the first population estimate for the region was made back in 2009.

Circles, Squares, and Roads Built to a Plan

The newly documented earthworks come in several recognizable forms. Geometric ditched enclosures, known as geoglyphs, range from small sites under half a hectare up to monumental structures nearly 50 hectares in size, with excavated ditches 9 to 13 meters wide and as much as 5 meters deep. Researchers also found that embanked enclosures without ditches, previously undetectable by satellite, were far more common than expected, and that many earthworks form larger clusters of up to eight connected enclosures.

Radiocarbon dating places construction of these geoglyphs between roughly 600 BC and AD 850, spanning nearly 1,500 years of continuous building and maintenance. The scale of the effort required real coordination. Building and sustaining these structures across such a long stretch of time would have demanded a substantial workforce, organized division of labor, and a working understanding of geometry, all directed toward sites that researchers believe functioned as public, ceremonial, and political gathering places rather than permanent, defended settlements.

Feeding a Population Without Clearing the Forest

One of the study’s most significant findings concerns how the Aquiry civilization sustained such a large population without stripping the rainforest bare. Researchers found a clear correspondence between the presence of earthworks and stands of domesticated and semi-domesticated tree species, particularly Brazil nut trees, along with several palm species including peach palm, bacaba, and uricuri. Macrofossil evidence recovered from excavations confirms these trees were important protein and nutrition sources for local communities, and many of the same species still grow around earthwork sites today.

Phytolith evidence also points to cultivation of maize and squash at geoglyph sites, while historical Spanish accounts from the sixteenth and seventeenth centuries describe manioc, sweet potato, chili peppers, beans, and peanuts as likely common crops as well. Rather than clearing large areas of forest for agriculture, researchers believe Aquiry communities practiced a form of forest stewardship, cultivating food trees and useful plants within a landscape that remained substantially forested, aided by unusually nutrient-rich soil confirmed by recent base cation concentration mapping of the region.

From 60,000 People to as Many as 3 Million

Population estimates for the region have climbed dramatically as the evidence has grown. The original 2009 estimate, based on roughly 200 known earthworks and the labor required to build and maintain them, put the population at about 60,000 people. With the new LiDAR-driven figure of 24,000 to 30,000 total earthworks, researchers recalculated using a combination of methods, including comparison with later precolonial mound villages in the same region and ethnographic data on similar living communities.

Using an estimated 300 people per average earthwork and accounting for the 25 to 60 percent of structures likely in simultaneous use during the civilization’s apparent population peak between AD 100 and 300, the team arrived at a total population of roughly 1.25 to 3 million people, and potentially as high as 3.8 million once accounting for structures that remain completely hidden beneath dense canopy the lasers couldn’t fully penetrate. For comparison, that would mean population densities in the civilization’s core area reaching 13.6 to 32.6 people per square kilometer, comparable to some late medieval German towns of the same era.

A Bigger Question for the Whole Amazon

This LiDAR survey covered less than 3 percent of Greater Amazonia, yet the Aquiry cultural area alone now appears to contain roughly as many earthworks as had previously been estimated for the entire Amazon basin combined. That comparison alone reshapes long-standing assumptions about how densely populated the precolonial Amazon really was.

The researchers are careful to frame their population estimate as specific to this one region, but they note the implications could extend much further. If similarly dense concentrations of earthworks turn up elsewhere in Amazonia as more LiDAR surveys are conducted, the total precolonial population of the entire Amazon basin, along with our understanding of its long-term effects on soil composition, forest structure, biodiversity, and even regional climate modeling, may need to be substantially reevaluated.

Sources

Nature