Over 20,000 Ancient Earthworks in the Amazon Reshape Debate on Precolonial Settlement and Forest Conservation

A Nature study (July 29, 2026) documents over 20,000 precolonial earthworks — mostly geoglyphs — across the Southwest Amazon, radiocarbon-dated to roughly 2,500 years. The scale challenges the view that the basin could not sustain large, complex societies and complicates conservation models treating the forest as a pristine baseline. Indigenous land-rights discussions may also be affected.