CHICAGO — For thousands of years, indigenous peoples of the Amazon may have intentionally created fertile soil for farming.
At archaeological sites in the Amazon basin, mysterious patches of unusually fertile soil dot the landscape. Scientists have long debated the origin of this “dark earth,” which is darker and more carbon-rich than the surrounding soil.
Now researchers have shown that the indigenous Kuikuro people of southeastern Brazil deliberately create similar soil around their villages. The finding, presented at the December 16 meeting of the American Geophysical Union, adds evidence to the idea that ancient Amazonians also intentionally prepared such soil.
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The fact that Kuikuro people are making dark earth today is “a pretty strong argument” that people did it in the past, says Duke University geochemist Paul Baker, who was not involved in the study.
By doing so, these early inhabitants may have inadvertently stored vast amounts of carbon in the soil, says study leader Taylor Perron, an earth scientist at MIT. The technique, he says, could provide a blueprint for developing methods to sustainably lock atmospheric carbon in tropical soils, helping to combat climate change.
Indigenous people have altered the Amazon for thousands of years
The Western world has long considered the Amazon to be a vast desert that was relatively untouched before the arrival of Europeans. On the same subject : Roland-Story sports overview: RS football team achieves first victory. Central to this argument is the idea that the Amazon’s soil, which is nutrient-poor like other tropical soils, did not allow its inhabitants to develop agriculture to the extent necessary to support complex societies.
But archeological discoveries in recent decades—including the discovery of ancient urban centers in the present-day Bolivian Amazon—have shown that humans were actively shaping the Amazon thousands of years before Europeans arrived (SN: 5/25). /22).
Most modern scientists agree that the presence of dark soil near archaeological sites means that ancient Amazonians used this soil to grow crops. But while some archaeologists argue that humans created the soil on purpose, others argue that the dark earth was formed through geological processes.
Perron and colleagues reviewed interviews with Kuikuro people conducted by a Kuikuro filmmaker in 2018. These conversations revealed that Kuikuro villagers actively make dark earth – Kuikuro eegepe – using ashes, food scraps and controlled burns.
“If you plant where there is no eege, the soil is weak,” explained elder Kanu Kuikuro in an interview. “That’s why we throw away the ash, cassava peels and cassava pulp.”
The researchers collected soil samples from Kuikuro villages and archaeological sites in Brazil’s Xingu River basin. Perron says the team found striking similarities between dark earth samples from ancient and modern sites. Both were much less acidic than the surrounding soils—probably due to the neutralizing effect of the ash—and contained more plant-friendly nutrients.
Dark earth could store a lot of carbon in the Amazon
These analyzes also showed that dark earth contains, on average, twice as much carbon as surrounding soils. To see also : ‘The Boys’ Isn’t Show No. 1 More Prime Video. Infrared scans of the Xingu region suggest that the region is covered in dark earth, and about 9 megatons of carbon, the annual carbon dioxide emissions of a small industrialized nation, may have gone undetected in the region, scientists said at the meeting.
While that number is preliminary, it could increase to roughly the level of the United States’ annual carbon emissions if all of the Amazon’s dark land is taken into account, Perron says.
How much carbon is actually stored in the Amazon could help improve climate simulations. But the researchers’ estimates are “a huge extrapolation from a very small data set,” warns Baker — a sentiment echoed by Perron.
More data is needed to determine the true value of the carbon stored in the Amazon’s dark ground, says Johns Hopkins University geographer Antoinette WinklerPrins, who was not involved in the study. Still, the study has profound implications for the past and future of the Amazon, he says.
First, the technique highlights how ancient humans were able to thrive in the Amazon by developing sustainable agriculture that served as a carbon sequestration technique. As more and more greenhouse gases are released into the atmosphere, turning the dark earth – or something similar – could be a method of mitigating climate change while supporting agriculture in the tropics.
“In the ancient past, people figured out how to store a lot of carbon for hundreds or even thousands of years,” says Perron. “Maybe we can learn something from this.”
