I, AS, B-- In the past few years, a small but growing group of researchers has been investigating terra preta, a rich, black soil that is believed to have sustained large settlements in Amazonia for 2 millennia. By understanding how indigenous groups created these so-called Amazonian dark earths, these researchers hope, today's scientists might be able to transform some of the region's nutrient-poor soils into new terra preta. Indeed, experimental programs to produce "terra preta nova" have already begun.