Terras pretas: Approaches to formation processes in a new paradigm

Terras pretas (Amazonian Dark Earths) are a remarkable kind of archaeological site found in the Amazon region. Rich in cultural artifacts and other occupational debris, these dark anthropogenic soil matrices are very fertile, presenting high levels of organic carbon, phosphorus, calcium, magnesium, zinc, and manganese. Their high nutrient levels come from decomposed organic matter, including remains of fish, shellfish, game, and other refuse, while their dark color has been linked to residual charcoal from intentional fires associated with daily activities and landscape management. Studies of anthropogenic earths in the Amazon have a deep history, as much in the geosciences as in archaeology and other historical sciences. Terras pretas have been studied as evidence of a major shift in human-environment relations, but also within the lens of environmental resiliency and sustainability. We review representative studies from various disciplinary fields and trace the development of knowledge about terra preta. We present a growing consensus with regard to the origin and significance of anthropogenic soils, concomitant with increased efforts toward interdisciplinary study. We argue that terras pretas constitute a genuinely interdisciplinary research topic that bridges scientific and traditional knowledge and applied contexts.