Study details ancient earthworks construction in the Amazon

Feb. 6 (UPI) -- Scientists have discovered more than 450 earthworks in the western Brazilian Amazon. The large geometrical geoglyphs in the Brazilian state of Acre were constructed by indigenous people more two thousand years ago, prior to the arrival of European people.

For most of their history, the geoglyphs, large ditched enclosures, remained hidden by trees. Modern deforestation has revealed their presence.

"The fact that these sites lay hidden for centuries beneath mature rainforest really challenges the idea that Amazonian forests are 'pristine ecosystems,'" Jennifer Watling, a post-doctoral researcher at the Museum of Archaeology and Ethnography at the University of Sao Paolo, said in a news release. "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."

Analysis suggests the land around the geoglyphs was altered for thousands of years, but never on a grand scale -- no clearcutting or field burning. Instead, small clearings were made to allow for the creation of the earthworks. Indigenous people also altered the forest by encouraging the growth of preferred species.

"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," Watling said.

Watling was working toward her PhD at the University of Exeter when the research was conducted.

Because few artifacts have been recovered from the earthworks, Watling and her colleagues don't believe the buildings served as shelter or villages. They were likely gathering places with spiritual significance -- gathering places managed with a refined ecological consciousness.

"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," she said. "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 research was published in the journal Proceedings of the National Academy of Sciences.