Agricultural settlements thrived in the Amazon 4,500 years ago, introducing new plants that have changed the way the rainforest has developed up to the present day.

A major new study reveals that early farming communities lived in the rainforest as far back as 2,500 BC, explaining why archaeological sites in the Amazon are replete with edible plants more than other parts of the forest.

The study is the first of its kind to analyze the long-term history of human use of land in the Amazon. It also provides evidence that the Amazon is not unscathed by human hands as previously thought.

Ancient Farmers In The Amazon

A team of archaeologists, ecologists, and botanists from the University of Exeter has found that ancient farmers planted new crops and edible trees in the Brazilian region of the Amazon on the eastern portion of the rainforest.

In a paper published in the journal Nature Plants, the team says early farmers used the lands of the Amazon extensively to grow food for their growing populations.

However, unlike large-scale industrial farmers, early communities maintained a closed-canopy forest by continuously nourishing the soil to keep it from running out of nutrients.

Crops Planted In The Amazon

The researchers studied samples of pollen, plants, and charcoal extracted from the soil in archaeological sites as well as sediments taken from a nearby lake.

A detailed analysis of these samples revealed that Amazonian farmers planted corn, sweet potato, squash, and cassava at least 4,500 years ago. Early communities also relied on fishing in the lakes and tributaries of the Amazon River.

As the farmers increased the amount of crops they planted, they also improved the levels of nutrition in the soil by burning and adding manure and other waste products.

None of these farming communities have survived. However, the impact of their activities in the Amazon can be seen as more edible plants are seen in areas where they once lived in.

Nutrient-Rich Earth

Lead author Yoshi Maezumi, a paleoecologist at the University of Exeter, says the farmers developed what is called Amazonian Dark Earths.

These ADEs are a nutrient-rich soil that allowed early farming communities to continue farming without depleting the soil of its nutrients. It also helped them grow corn and other crops in areas with generally poor soils.

Although these indigenous farmers most likely cut down some trees beneath the canopy, they kept a closed canopy by reusing the soil instead of clearing trees to expand their farming to other areas.

"This is a very different use of the land to that of today, where large areas of land in the Amazon is cleared and planted for industrial scale grain, soya bean farming, and cattle grazing," says Maezumi. "We hope modern conservationists can learn lessons from indigenous land use in the Amazon to inform management decisions about how to safeguard modern forests."

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