Pre-Columbian farmers ways of fertilizing the soil still impacts Amazon’s biodiversity

Pre-Columbian farmers ways of fertilizing the soil still impacts on Amazon's biodiversity

Long before Columbus discovered the American continent, there lived in the vast Amazon people who grew their own food there. To get the most out of their fields, they developed a special way of fertilizing. They mixed the soil with charcoal and food scraps, creating a dark layer of soil visible to this day in some places. And that layer of soil still affects biodiversity in the Amazon, according to an international team of researchers in the journal Global Ecology and Biogeography.

On the dark soil, very different plant species were found to be in the field than on the unprocessed soil, and so the dark soil contributes to the biodiversity of the area, according to the researchers. For example, on the processed earth, many more edible plant species and trees with edible fruits grew.

The researchers draw their conclusions based on field research. They traveled to the Amazon and compared the soil mixed with charcoal and food scraps with soil that had not been processed by the old farmers. And they looked at what exactly was growing on that ground. They found that the dark – including charcoal permeated – soil had a much higher pH and harbored more nutrients. The soil was therefore much more fertile than the land that the old farmers had not taken care of.

It is believed that the old farmers used dark soil to grow various crops. And in the meantime, so-called forest farming was done in the adjacent forests without dark soil. This involves combining forestry and agriculture in one area. It must have been a success. But after the Europeans colonized the area, the indigenous populations collapsed and the carefully processed fields were abandoned.

The research reveals for the first time the extent to which pre-Columbian farmers have influenced the biodiversity of the Amazon. “Pre-Columbian indigenous people, who fertilized the nutrient-poor land of the Amazon for at least 5,000 years, have created an impressive legacy with the dark earth,” researcher Ben Hur Marimon Jr.

Today, however, there are (indigenous) people who successfully grow their crops on the fields farmed by pre-Columbian farmers. However, it is assumed that only a fraction of the pre-Columbian fields are back in use; much of it would still be hidden in the Amazon and – unseen – would still contribute to the growth of trees and regional biodiversity.

Although the Pre-Columbian farmers have been making their mark on the Amazon through their dark soil for many centuries, their legacy is now under threat. The areas with the characteristic dark soil and everything that grows on them are increasingly falling prey to illegal logging.

Based on what we now know – thanks to this research among others – of the dark soil, this should not happen at all, the researchers say. The dark soil and the rich vegetation that can be found thereon is not only culturally, but also biologically of great value and should, therefore, be preserved for future generations.


” Innovation by ancient farmers adds to biodiversity of the Amazon, study shows ” – University of Exeter (Eurekalert)