Hidden Treasure of Amazonian Dark Earth: How It Supports Forest Restoration and Conservation

Did you know that there is a type of soil in the Amazon rainforest that is so fertile and black that it looks like chocolate cake? This soil is called Amazonian dark earth (ADE) or terra preta, and it was not made by nature, but by humans.

That's right, thousands of years ago, the people who lived in the Amazon added charcoal, animal bones, pottery, compost, and manure to the soil to make it better for growing crops.

They also created a living soil full of friendly bacteria and archaea that help plants thrive.

How ADE boosts plant growth

(Photo : PEDRO PARDO/AFP via Getty Images)

Scientists from Brazil have discovered that ADE can make plants grow faster and stronger than normal soil, as per Phys.org.

They did some experiments to see what happens when they plant grass and trees in pots with different types of soil.

They used control soil, the normal soil you find in farms, a mix of control soil and ADE, and 100% ADE. They then watched how the plants grew over time.

They found that ADE made all the plants grow better, especially cedro blanco (Cedrela fissilis), a tree that belongs to the final stage of forest recovery.

Cedro blanco seedlings that grew in 100% ADE were 2.5 times taller and had 3 times more weight than those that grew in control soil after 120 days.

ADE also made the soil more alive and diverse with bacteria and archaea, which could do amazing things like fixing nitrogen from the air, making phosphorus more available, producing plant hormones and fighting diseases

Also Read: Experts Reveal Why There Are No Bridges in the Amazon River

How ADE can help us restore forests and fight climate change

Scientists think ADE could be a 'secret weapon' to help us restore forests not only in the Amazon, where we have lost 18% or about 780,000 km2 of forest since the 1970s but worldwide.

By copying the recipe of ADE, especially its microbes, we could make reforestation projects faster and more successful.

"Here we show that the use of ADEs can enhance the growth of pasture and trees due to their high levels of nutrients, as well as to the presence of beneficial bacteria and archaea in the soil microbial community," said joint lead author Luís Felipe Zagatto, a graduate student at the Center for Nuclear Energy in Agriculture of São Paulo University, Brazil, as per Frontiers.

This means that knowledge of the 'ingredients' that make ADEs so very fertile could be applied to help speed up ecological restoration projects.

But that's not all. ADE could also help us fight climate change by storing more carbon in soils and plants. ADE contains stable organic matter from charcoal, which can keep carbon for thousands of years.

Plus, ADE could reduce the need for chemical fertilizers and pesticides, which are bad for the environment.

The History and Mystery of ADE

ADE is not a recent discovery. It was first reported by Spanish explorers who visited the Amazon in the 16th century, as per Science Focus.

They were amazed by the contrast between the dark and fertile soils cultivated by the natives and the surrounding infertile soils covered by forest. They also noticed that these soils contained pottery fragments and human bones.

However, it was not until the 20th century that scientists began to study ADE in more detail. They found out that ADE covers about 10% of Amazonia, mostly along rivers and ancient settlements.

They also estimated that ADE was created between 450 BCE and 950 CE by millions of Amerindian people who lived in complex societies before European contact.

The exact methods and motives behind ADE creation are still unknown. Some researchers think that ADE was intentionally produced as a way to improve soil fertility for agriculture.

Others suggest that ADE was an accidental by-product of waste disposal and fire management practices. Some even propose that ADE was part of a ritual or symbolic system related to ancestor worship or cosmology.

Whatever the case may be, ADE is a remarkable legacy of human ingenuity and adaptation to a challenging environment. It also shows us how humans can transform nature in positive ways without destroying it.