Revitalizing the Amazon Rainforest with Ancient Soil Techniques

 The Amazon rainforest, a breathtaking hotspot of biodiversity, has seen approximately 18% of its area affected since the 1970s. To rejuvenate this vital ecosystem, researchers are turning to fertile soil created by Amerindians around 2,000 years ago.

In the past, Amerindians inhabited the region now recognized as the Amazon, unintentionally producing a highly fertile soil. This soil, known as Amazonian Dark Earth (ADE) or Terra Preta, formed from the combination of charcoal from bonfires, manure, animal remains, and broken pottery pieces.

The Soil's Potential to Restore the Amazon Rainforest

The Amazon rainforest soil not only holds traces of ancient human activity but also supports a thriving microbiome. Researchers at the University of São Paulo in Brazil conducted a simulation to investigate whether ADE could aid in restoring the Amazon's lush forests. They filled containers with three types of soil: control soil from cultivated Amazon areas, a mixture of cultivated soil with 20% ADE, and 100% pure ADE.

The scientists then sowed grass in each container and, once it matured, cut it back, leaving the roots intact. They subsequently planted various trees in the containers, mimicking the natural process of cropland transforming into grassland and eventually forest.

After 90 days of tree growth, the researchers observed that although all soils had fewer nutrients due to plant absorption, the ADE soils retained more nutrients than the control soil. Additionally, both ADE soils demonstrated greater bacterial and microbial biodiversity compared to the control.

The Microorganisms Found in ADE

Anderson Santos de Freitas, the joint lead author, explained in an interview with New Atlas, "Microbes transform soil chemical particles into nutrients that can be absorbed by plants. Our data showed that ADE contains microorganisms that are better at this transformation of soils, thus providing more resources for plant development." He further noted that ADE soils contained a higher number of beneficial bacterial families, such as Paenibacillaceae, Planococcaceae, Micromonosporaceae, and Hyphomicrobiaceae.

The Remarkable ADE Soil

It's astounding that, when cultivated in this microorganism-rich soil, the dry mass of the harvested grass increased 3.4 times in the 20% ADE mixture and even reached 8.1 times in the 100% ADE soil. The trees exhibited similar improvements. In the 20% ADE mixture, tree growth was 2.1 to 5.2 times taller per species compared to control soil, and in the 100% ADE soil, they grew up to 6.3 times taller.

While the research team advises against using actual ADE for Amazon rainforest restoration efforts, they suggest that creating soil abundant in the same microbes found in ADE could yield similar results, thereby promoting the growth of new forests on exhausted farmlands.

A Millennia-Long Process

"ADE took thousands of years to form and would require an equal amount of time to regenerate naturally if exploited," stated senior study author Siu Mui Tsai. "Instead of using the ADE itself, we recommend replicating its characteristics, particularly its microorganisms, for future ecological restoration endeavors."

This research was published in the journal Frontiers in Soil Science.

In conclusion, the fertile ADE soil, with its rich microbiome and enhanced nutrient retention, offers a promising solution for restoring the Amazon rainforest's health and biodiversity. By leveraging ancient Amerindian soil techniques, we may be able to rejuvenate this vital ecosystem and protect it for future generations.