The human effect – How people have influenced the Amazon rainforest

It's tempting to see the Amazon's rainforests as pristine environments mostly unaffected by mankind. It's equally tempting to see indigenous people as having very little impact on the natural forest environment. But new research reveals humans have an awful lot to do with the way Amazon forests have developed over the 8000 years or so that people have lived there.

Proof that Pre-Colombians colonised the Amazon and thrived there

New research reveals that the area's powerful Pre-Colombian civilisation changed the region profoundly. A team from Naturalis Biodiversity Center and the Amazon Tree Diversity Network compared the distribution of 85 tree species, cross-referencing them with known archaeological sites. What they found was a surprise. It looks like the trees that were once domesticated by the pre-Columbians still dominate the forest, being five times more likely to grow around ruined cities and settlements than non-domesticated trees.

Out with the old, in with the new

The finding is already generating heated debate amongst scientists, challenging the old view that somehow, thousands of years of human occupation didn't really impact today's levels of diversity. And it's interesting to see which trees these ancient people valued most. They cultivated Brazil nuts and cacao, rubber, acai palm, cashew, caimito and tucuma palm, all species that are widely found to this day around the ruins of their cities. It looks like the Amazon is not as untouched as everyone assumed.

Why does it matter?

The results matter because they can be used to examine the agricultural history of the region. The Amazon is unbelievably vast, which usually makes research tricky, but the sheer quantity of new archaeological sites found recently, partly thanks to good quality satellite imagery, reveal the pre-Columbians' powerful ecological legacy.

No longer can we claim that the Amazon rainforest was only sparsely populated before Europeans arrived on the scene. The pre-Columbians lived and thrived in the Amazon region, just as they did across the rest of  South America.

There's some very good news too – interestingly, the domesticated tree species are tipped to re-colonise deforested areas more readily than non-domesticated species, and they can do it without help from humans.

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