Impact of pre-Columbian “geoglyph” builders on Amazonian forests

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Over 450 pre-Columbian (pre-AD1492) geometric ditched enclosures (‘geoglyphs’) occupy ~13,000 km2 of Acre state, Brazil, representing a key discovery of Amazonian archaeology. These huge earthworks were concealed for centuries under terra firme (upland interfluvial) rainforest, directly challenging the ‘pristine’ status of this ecosystem and its perceived vulnerability to human impacts. We reconstruct the environmental context of geoglyph construction and the nature, extent and legacy of associated human impacts. We show that bamboo forest dominated the region for ≥6000 y and that only small, temporary clearings were made to build the geoglyphs; however, construction occurred within anthropogenic forest that had been actively managed for millennia. In the absence of widespread deforestation, exploitation of forest products shaped a largely forested landscape that survived intact until the late 20th century.Gregorio de Souza for creating Fig. 1, and F. Braga for fieldwork support. Funding for this research was granted by the United Kingdom Arts and Humanities Research Council (AH/J500173/1) (to J.W.), Natural Environment Research Council (NERC) (NE/B501504) (to N.J.L.), NERC/OxCal Radiocarbon Fund (2013/2/8) (to J.W and J.I.), and National Geographic Society and Exploration Europe (GEFNE14-11) (to F.E.M. and J.I.)