Rainforest researchers hit pay dirt

It shouldn’t be there, but it is. Deep in the central Amazonian rainforest lies a rich, black soil known locally as terra preta do Indio (Indian dark earth) that farmers have worked for years with minimal fertilization. A Brazilian-American archeological team believed terra preta, which may cover 10 percent of Amazonia, was the product of intense habitation by Amerindian populations who flourished in the area for two millennia, but they recently unearthed evidence that societies lived and farmed in the area up to 11,000 years ago.

As reported in the August 9 issue of the journal Science, such long-lasting fertility is an anomaly in the tropics, where punishing conditions make the land highly acidic, low in organic matter and essential nutrients, and nearly incapable of sustaining life.

In 1994, James Petersen, associate professor and chair of anthropology at the University of Vermont, and Michael Heckenberger, now at the University of Florida, investigated their first terra preta deposit on a riverbank near Açutuba. The three-kilometer site was thick with broken pieces of ceramic, relics of a large, ancient society. To date, they and fellow researchers have excavated four sites and explored 30 others near the junction of the Amazon and Rio Negro.

What researchers find most remarkable is that instead of destroying the soil, the indigenous inhabitants improved it – something ecologists don’t know how to do today. Although the project is in its early stages, modern scientists hope to learn the principles behind terra preta. The ability to reproduce the super-fertile soil could have broad impact, making it possible to sustain intensive agriculture in the Amazon and other hot regions.