Did ancient tribes shaped the Amazon?

New research shows the Amazon was partly shaped by indigenous peoples thousands of years ago.

Whether pre-Columbian societies altered the Amazonian rainforest and landscape or not is something that has always been debated. Nonetheless it is common to assume certain species thrived thanks to natural selection rather than human intervention.

But now, a study published in Science Magazine shows tree communities across the basin were in part structured by historical human use.

Researchers analyzed human impact on the forests by overlapping more than 3,000 known archaeological sites in the Amazon with the distribution and abundance of over 1,000 forest surveys. They focused on 85 tree species that were known to be domesticated by indigenous communities for shelter and food among other uses.

"Some of the tree species that are abundant in Amazonian forests today, like cacao, acai, and Brazil nut, are probably common because they were planted by people who lived there long before the arrival of European colonists," said Nigel Pitman, co-author of the study to Science Daily.

The team was made up of hundreds of ecologists and social scientists and was led by Carolina Levis, a PhD student at Brazil National Institute for Amazonian Research (INPA) and Wagenigen University and Research in the Netherlands.

“Domesticated species are five times more likely than non-domesticated species to be hyperdominant,” the study reads. “The relative abundance and richness of domesticated species increase in forests on and around archaeological sites. […] Our analyses indicate that modern tree communities in Amazonia are structured to an important extent by a long history of plant domestication by Amazonian peoples.”

Surprisingly this was also the case of some remote mature forests which, as Pitman added, were thought to be “pristine and undisturbed.”

According to Hans ter Steege of Naturalis Biodiversity Center and coordinator of the Amazon tree Diversity Network, “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."

More so, “this lays to rest the long-standing myth of the 'empty Amazon'," told Phys.org Charles Clement, senior researcher at INPA, Manaus, and a coauthor of the study.

"Early European naturalists reported scattered indigenous populations living in huge and apparently virgin forests, and that idea has continued to fascinate the media, policy makers, development planners and even some scientists. This study confirms that even areas of the Amazon that look empty today are crowded with ancient footprints."

Nonetheless the team cautioned that there is still a lot to learn about how ancient tribes might have affected the species composition of the Amazon.

Meanwhile, Flávia Costa, another researcher with INPA and study co-author told Mongabay these findings “have important implications for conservation,” especially considering many domesticated tree species are crucial to the livelihoods of Amazonian people today.

“We have shown that the southwestern and eastern regions concentrate the most domesticated species, and these are the regions where most forest degradation and loss is occurring,” she added. “Southwestern and eastern Amazonia may not be considered classical biodiversity hotspots, but should be top conservation priorities as reservoirs of high value forests for human populations.”

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