The indigenous people may have created the ‘dark lands’ of the Amazon on purpose

CHICAGO – The indigenous people in the Amazon deliberately created a fertile soil for thousands of years.

At archaeological sites across the Amazon River basin, the mysterious resurgence of fertile soil gives the landscape its distinctive features. Scholars have long debated the origin of this “dark earth,” which is darker in color than the surrounding earth and richer in carbon.

Already, researchers have learned that the indigenous Kuikuro people in southern Brazil actively create similar land around their villages. The discovery, which was presented on December 16 at the meeting of the American Geophysical Union, adds to the evidence for the idea that the Amazon long ago also built such an industry on its own.

The fact that the Kuikuro people are doing dark soil today is “a pretty strong argument” that people were doing it in the past as well, says Paul Baker, a geochemist at Duke University who was not involved in the research.

In doing so, these ancient inhabitants inadvertently stored large amounts of carbon in the soil, says study author Taylor Perron, an earth scientist at MIT. The technique, he says, could provide a blue print for developing ways to sustain atmospheric carbon in the tropics, helping to fight climate change.

Indigenous peoples have changed the Amazon for thousands of years

The Western world had long viewed the Amazon as a vast wilderness that was relatively untouched before the Europeans showed up. At the heart of this argument is the idea that the Amazon alone, which is poor in food like other tropical lands, has prevented its inhabitants from cultivating agriculture on the scale required to support complex societies.

But archaeological discoveries in recent decades – the discovery of ancient urban centers in the Amazonian areas of present-day Bolivia – show that people were actively shaping the Amazon for thousands of years before the arrival of Europeans.SN: 5/25/22).

Most scientists today agree that the presence of dark soil near archaeological sites means that long ago the Amazon used this soil to grow crops. But while some archaeologists argue that humans made the earth with energy, others argue that the dark earth was laid down by a geological process.

Perron and colleagues reviewed interviews with Kuikuro people by a Kuikuro filmmaker in 2018. Those interviews revealed that the Kuikuro villagers were actively blackening the land – eegepe in Kuikuro – using ashes, the food continues to burn and burn.

“When you plant where there is no eegepe, the soil is weak,” explained elder Kanu Kuikuro in one of the interviews. “That’s why we inject the ashes, cassava, peeled, cassava pulp.”

The researchers only collected samples from around Kuikuro villages and archaeological sites in Brazil’s Xingu river basin. The team found “striking similarities” between dark earth samples from ancient and modern sites, Petron says. Both were far less acidic than the surrounding soils—probably due to the way the ash decomposed—and contained higher levels of plant-friendly nutrients.

A dark earth could store a lot of carbon in the Amazon

These analyzes also revealed that dark soil holds twice as much carbon as the surrounding soil on average. Infrared scans of the Xingu region suggest an area of ​​dark pockmarked earth, and as much as 9 megatons of carbon — the annual carbon emissions of a small, industrial country — may have gone into the environment, the researchers reported. assembly

This number, while preliminary, could be inflated to roughly the annual carbon emissions of the United States when all the dark land across the Amazon is considered, Perron says.

Finding out how much carbon is actually stored in the Amazon could help improve climate simulations. But the researchers estimate “massive extrapolations from small datasets,” Baker cautions — a sentiment echoed by Perron.

Determining the true value of carbon stored in the Amazon’s dark soil will require more data, says Antoinette Winkler-Prins, a geographer at Johns Hopkins University who was not involved in the study. However, the research says Amazon’s “past and future” have “profound implications.”

For one, the art sheds light on how ancient humans were able to thrive in the Amazon by developing sustainable agriculture, which doubled as carbon-sequestration technology. As more and more greenhouse gases enter the atmosphere, darkening the earth or something similar, it may be a method of mitigating climate change while supporting agriculture in the tropics.

“People in the ancient past figured out how to store a lot of coal for hundreds or even thousands of years,” says Petron. “Maybe we can learn something from that.”