March 3 (UPI) -- The Amazon rainforest is a fertile place full of biodiversity. But it's not untouched by humans. New research shows the influence of indigenous people continues to shape the makeup of the forest today.
Analysis of species distribution within the Amazon proved domesticated trees and palms are five times more likely to be disproportionately abundant than non-domesticated species.
Researchers discovered the influence of early Amazonian people by overlaying forest survey maps and maps of some 3,000 pre-Columbian archaeological sites. In recent decades, scientists have found the remains of hundreds of ancient settlements in the Amazon.
Scientists measured the distribution of 85 tree species known to have been domesticated by indigenous people. They found the species were not only more likely to be present in general, but much more likely to be found close to ancient archaeological sites.
Amazonian peoples domesticated species like the cacao, acai and Brazil nut to harvest fruits and nuts and to build houses. Many of the species are distributed widely today and dominate large swaths of the rainforest -- a living legacy to the region's indigenous peoples.
It's unlikely all of these domesticated species were planted directly by humans. Instead, their presence likely created conditions that offered advantages to domesticated species. Domesticated species likely recolonized areas damaged by human activity.
"The finding promises to heat up a long-simmering debate among scientists about how thousands of years of human occupation in the Amazon basin have influenced modern-day patterns of Amazonian biodiversity, and challenges the view many of us ecologists had and still have of this huge area," Hans ter Steege, a researcher at the Naturalis Biodiversity Center in the Netherlands, said in a news release.
The findings, detailed in the journal Science, are a reminder that places that appear wild may be hiding unstudied human influences.
"It's not enough to study the environmental conditions that structure these communities of trees and palms," said lead study author Carolina Levis, a palaeoecologist at Wageningen University in the Netherlands. "We need to ask: 'What are the human influences in these communities?'"