Amazonian Dark Earth: A Key to Reversing Forest Degradation
A study published in BMC Ecology and Evolution in 2026 reveals that Amazonian dark earth (ADE) can significantly accelerate the restoration of degraded lands in Brazil. Researchers from the University of São Paulo’s Center for Nuclear Energy in Agriculture (CENA-USP), the Brazilian Agricultural Research Corporation (Embrapa) Western Amazon, and the National Institute of Amazonian Research (INPA) found that small amounts of this ancient organic-rich soil boosted native tree growth under real field conditions.
After 180 days, seedlings of the pink ipê (Handroanthus avellanedae) grown with modest amounts of ADE were up to 55% taller and had 88% larger stem diameters compared to those without the anthropogenic soil. Paricá (Schizolobium amazonicum) also showed strong responses, with 20% more growth and 15% larger stem diameters. The experiment was conducted from October 2022 to April 2023 at Embrapa Western Amazon’s Caldeirão Experimental Field in Iranduba, Amazonas state, in Manaus.
How Amazonian Dark Earth Works
Microbiome Engineering
Lead author Anderson Santos de Freitas, a researcher from CENA-USP, explained that ADE significantly altered the soil’s microbiota: it had little effect on bacterial diversity but increased fungal diversity, especially for pink ipê, and drove clear shifts in microbial composition, reducing pathogens and increasing beneficial micro-organisms and biocontrol agents. The soil functions as a biological inoculant that reconfigures the soil’s microbiome, making it more pathogen-suppressive and favorable to plant growth. Freitas highlighted that combined with fertility, this microbial effect explains ADE’s potential for sustainable ecological restoration.
Field Testing Beyond the Lab
The study aimed to test ADE microbes under real environmental conditions—rainfall, winds, surrounding vegetation, and soil characteristics. Seedlings were produced in a nursery with small amounts of dark earth and then transplanted into Ultisol (a soil type widely found in Brazil) planted with cassava. Scientists monitored development for six months, measuring height and diameter and collecting soil samples for physicochemical analyses and DNA sequencing. Results showed a reduction in potentially pathogenic organisms and an increase in beneficial microbes.
Conservation and Future Applications
Researchers emphasize that their goal is not to use ADE on a large scale in restoration. In Brazil, dark-earth sites are protected as archaeological and environmental heritage under federal law. The aim is to understand how this soil works and emulate its characteristics in the lab. The options under study include biochar (a carbon-rich charcoal) and isolation of micro-organisms present in ADE that stimulate plant growth. The future goal is to create bioinputs that replicate the biological benefits without disturbing original deposits.
Cautionary Perspectives
Wenceslau Geraldes Teixeira, an expert from Embrapa’s Soil division, cautioned that superficial readings could encourage illegal removal of ADE from the Amazon. He noted that commercial mining or extraction is a crime, and the real potential lies in scientific knowledge. He also raised methodological concerns: 290 cm³ (290 g) of ADE per plant might provide a nutritional start-up advantage, and there are huge variations among different dark-earth sites across the Amazon. In a study conducted in Bolivia, ADE led to high mortality in some tree species due to excess nutrients. Nonetheless, researchers agree that expanding knowledge about ADE is crucial for tropical ecological restoration in the face of climate change and deforestation.
This story was first published in Portuguese on June 29, 2026.