Airborne lasers have uncovered more than 20,000 precolonial earthworks beneath the Amazon rainforest, evidence of a sprawling civilisation that has been hiding in plain sight for centuries.

A study published on 29 July 2026 in the journal Nature used LiDAR — a laser-based surveying technology that fires pulses from aircraft through the canopy to map the ground below — to document the structures across the Brazilian state of Amazonas. The sheer scale surprised the researchers: over 20,000 distinct earthworks, ranging from geometric enclosures to raised causeways, spread across a region long assumed to have been sparsely populated before European contact.

The following day, ARTnews reported on aerial surveys in Brazil that produced further evidence of a pre-Columbian civilisation, building on the Nature findings (ARTnews).

How many people lived there? Science magazine, reporting on the study the same day it was published, wrote that the newly discovered earthworks suggest approximately 3 million people may have lived in roughly 3 per cent of the forest's total area (Science). That figure covers only the surveyed portion; the wider Amazon may hold many more undiscovered structures.

Brazilian researchers had been edging toward this picture for years. The Instituto Nacional de Pesquisas da Amazônia, a federal research body in Manaus, has hosted academic papers on its government website documenting pre-Columbian earthworks across the region. One such paper, by researcher R. Kalliolla, noted that more than 10,000 earthworks remain hidden throughout Amazonia — a figure the 2026 LiDAR survey has now dramatically expanded.

What the lasers found were not just a handful of isolated mounds. The earthworks include fortified villages, ceremonial plazas and road networks — the infrastructure of organised, settled societies, not small wandering bands. Geometric shapes, some spanning hundreds of metres, had been carved into the terrain and then swallowed by jungle growth over the centuries since they were abandoned.

The findings add to a growing body of evidence that the pre-Columbian Amazon was far more densely populated than twentieth-century historians believed. Earlier estimates held that the rainforest's poor soils could not support large populations. The earthworks suggest otherwise: these societies modified the landscape on a massive scale, and the forest that grew over their work preserved it.

What remains unknown is how many more earthworks lie beyond the surveyed area. The LiDAR flights covered only a fraction of the Amazon basin. Every new survey could add thousands more to the count.