Study Investigates Source of Amazon’s “Dark Earth”

CHICAGO, ILLINOIS—Science News reports that the ancient patches of fertile land known as Amazonian Dark Earths (ADEs) found near archaeological sites in the Amazon River basin may have been created intentionally, based upon a new study of the practices of the Kuikuro people, who live in southeastern Brazil. Some have argued that ADEs were formed through geologic processes, but the Kuikuro create enriched soil, known as eegepe, around their villages today with ash, food scraps, and controlled burns. Morgan J. Schmidt and Taylor Perron of the Massachusetts Institute of Technology and their colleagues compared samples of ADEs collected from areas around Kuikuro villages and archaeological sites in Brazil’s Xingu River basin and found that they are both far less acidic than the surrounding soils, perhaps as a result of the addition of ash. The ADEs also contained higher levels of nutrients needed for growing crops. Finally, the researchers found that the samples held about twice the amount of carbon than the surrounding soils. “People in the ancient past figured out a way to store lots of carbon for hundreds or even thousands of years,” Perron concluded. For more, go to "Dark Earth in the Amazon."