Over 20,000 precolonial earthworks in the Southwest Amazonia
NatureTL;DR
Imagine flying a special laser scanner over the Amazon jungle that can 'see through' the treetops, like X-ray vision for the ground. When scientists did this, they found over 20,000 geometric shapes — ditches, mounds, and enclosures — built by ancient people long before Europeans arrived. These aren't small things: they're massive earthen structures, like monuments. This means the Amazon rainforest, which most people picture as empty wilderness, was actually home to millions of people who built cities and shaped the landscape. Think of it like discovering that a forest you thought was wild was actually someone's ancient garden on a continental scale.
Abstract Numerous geometric earthworks have been found in southwestern Amazonia, evidence of a monument-building precolonial civilization 1–3 . This knowledge has contributed to the discussion about the deep history and the precolonial urbanism of Amazonia, its sociocultural contexts and its environmental legacy 2,4–8 . Estimates of the geographical extent and population size of the forest civilization have remained weak, because the detection of earthworks has been almost exclusively limited to deforested areas where vegetation does not completely hide the structures. Here we used canopy-penetrating LiDAR data over 4,430 km of flight to define the geographical distribution and quantity of earthworks in this region better. On the basis of both existing data and our LiDAR documentation, we show that this cultural area alone contains as many earthworks as previously estimated for the whole of Amazonia. We also propose that the total human population of the area in 100–300 ad was 1.25–3 million people. If similar results are found elsewhere in Amazonia, the total precolonial population density and its effect on the current Amazonian soil and forest structure, biodiversity and even some modelling of the global climate should be re-evaluated.
- 1LiDAR data collected over 4,430 km of flight revealed over 20,000 precolonial earthworks in southwestern Amazonia, far exceeding previous estimates for the entire Amazon basin.
- 2The southwestern Amazonia cultural area alone contains as many earthworks as had been previously estimated for the whole of Amazonia.
- 3The study proposes that the total human population of the area in 100–300 AD was between 1.25 and 3 million people.
- 4Earthwork detection was extended beyond deforested areas into forested regions using canopy-penetrating LiDAR technology.
- 5Findings suggest that precolonial population density and its effects on Amazonian soil, forest structure, biodiversity, and global climate models should be re-evaluated.
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