Just to highlight the part that I personally find most interesting: Terra preta, Woods guesses, covers at least 10 percent of Amazonia, an area the size of Fra

Just to highlight the part that I personally find most interesting: Terra preta, Woods guesses, covers at least 10 percent of Amazonia, an area the size of France. It has amazing properties, he says. Tropical rain doesn't leach nutrients from terra preta fields; instead the soil, so to speak, fights back. Not far from Painted Rock Cave is a 300-acre area with a two-foot layer of terra preta quarried by locals for potting soil. The bottom third of the layer is never removed, workers there explain, because over time it will re-create the original soil layer in its initial thickness. The reason, scientists suspect, is that terra preta is generated by a special suite of microorganisms that resists depletion. "Apparently," Woods and the Wisconsin geographer Joseph M. McCann argued in a presentation last summer, "at some threshold level ... dark earth attains the capacity to perpetuate—even regenerate itself—thus behaving more like a living 'super'-organism than an inert material." [...] Not all Xingu cultures left behind this living earth, they discovered. But the ones that did generated it rapidly—suggesting to Woods that terra preta was created deliberately. In a process reminiscent of dropping microorganism-rich starter into plain dough to create sourdough bread, Amazonian peoples, he believes, inoculated bad soil with a transforming bacterial charge. [...] Wikipedia has, of course, an article on terra preta: http://en.wikipedia.org/wiki/Terra_preta http://en.wikipedia.org/wiki/Terra_preta Most interesting is modern attempts by scientists to effectively reverse-engineer the soil; using a combination of crude charcoal, organic compost, and microorganism cultures to convert poor soils into something approximating the robust, fertile terra preta.