Jennifer Watling, post-doctoral researcher at the Museum of Archaeology and Ethnography, University of São Paulo, carried out the study of the sites while studying for a PhD at the University of Exeter.

"The fact that these sites lay hidden for centuries beneath mature rainforest really challenges the idea that Amazonian forests are 'pristine ecosystems," said Dr. Watling. "We immediately wanted to know whether the region was already forested when the geoglyphs were built, and to what extent people impacted the landscape to build these earthworks."



Members of Dr. Watling's team were able to reconstruct 6000 years of history surrounding the sites, and they found that humans had heavily altered bamboo forests for millennia in order to create small, temporary clearings to build the geoglyphs. Instead of burning away vegetation, the ancient native inhabitants used horticultural methods to promote economically valuable tree species such as palms, creating a kind of 'prehistoric supermarket' of useful forest products. This suggests that the biodiversity of some of the Amazon's flora may be a result of these inhabitant's agricultural husbandry.

"Despite the huge number and density of geoglyph sites in the region, we can be certain that Acre's forests were never cleared as extensively, or for as long, as they have been in recent years," said Watling. "Our evidence that Amazonian forests have been managed by indigenous peoples long before European Contact should not be cited as justification for the destructive, unsustainable land-use practiced today. It should instead serve to highlight the ingenuity of past subsistence regimes that did not lead to forest degradation, and the importance of indigenous knowledge for finding more sustainable land-use alternatives".

The full study will be released in the Proceedings of the National Academy of Sciences of the USA and involved researchers from the universities of Exeter, Reading and Swansea (UK), São Paulo, Belém and Acre (Brazil). The research was funded by the Arts and Humanities Research Council, National Geographic, and the Natural Environment Research Council Radiocarbon Facility.