Domesticated species such as the Brazil nut are of economic importance today. Image courtesy of Ted Feldpausch.
Ancient peoples shaped Amazon rainforest
The Amazon rainforest was shaped by ancient people who lived there, new research reveals.
The study found that 85 tree species domesticated by pre-Columbian peoples remain more common in forests close to ancient settlements.
An international team of ecologists and social scientists – led by Carolina Levis, from Brazil’s National Institute for Amazonian Research and Wageningen University and Research Center in the Netherlands – carried out the research, which is published in the journal Science.
It shows that tree species domesticated and distributed throughout the Amazon Basin by indigenous peoples before colonisation by Europeans continue to play an important role in modern-day forests.
These new findings strongly refute the idea that Amazonian forests have been largely untouched by humans.
"We know that pre-Columbian peoples transformed vegetation in small areas, usually along streams, at the scale of several hectares by enriching soils for crop production,” said co-author Dr Ted Feldpausch, a tropical forest ecologist at the University of Exeter.
“However, it has been unclear whether there were more widespread changes in forests across the Amazon Basin due to humans.
“We have found that some domesticated species are more common in forests in a wider area beyond the archaeological sites, suggesting pre-Columbian peoples, through selection of useful tree species, played a role in modifying the surrounding tree composition in forests found today.
“This ancient legacy has an impact on the lives of modern inhabitants. For example, domesticated species such as cacao, Brazil nut, and the palm açai are of economic importance today for small-scale farmers living within or in close proximity to the forest.”
Carolina Levis said: "For many years, ecological studies ignored the influence of pre-Columbian peoples on the forests we see today. We found that a quarter of Amazonia’s domesticated species are widely distributed in the basin and dominate large expanses of forest. These results clearly indicate that the Amazonian flora is in part a surviving heritage of its past inhabitants.”
The team made the discovery by overlaying data from more than 1,000 forest surveys of the Amazon Tree Diversity Network on a map of more than 3,000 archaeological sites across the Amazon. By comparing forest composition at varying distances from archaeological sites, their analysis generated the first Amazon-wide picture of how pre-Columbian peoples influenced Amazonian biodiversity.
“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,” said Hans ter Steege, of Naturalis Biodiversity Center and coordinator of the Amazon Tree Diversity Network.
The study focused on 85 tree species known to have been domesticated by Amazonian peoples for food, shelter or other uses over the last several thousand years.
While the relatively small number of domesticated tree species used in the study was sufficient to reveal a strong human signal in modern forests, the authors point out that the signal may be even stronger than they documented, since hundreds of other Amazonian tree species were also managed by pre-Columbian peoples but not domesticated.
Untangling the complex interplay of historical, environmental and ecological factors structuring approximately 16,000-species Amazonian tree flora remains a focus of the team’s work.
The question is pressing, since both types of pre-Columbian heritage – archaeological sites and forests with a strong historical component – are at risk from deforestation, degradation, roadbuilding, mining and other threats.
Date: 6 March 2017