Morgan Schmidt

MORGAN J. SCHMIDT, Massachusetts Institute of Technology, Cambridge, Massachusetts, received a grant in April 2018 to aid research on “Ethnoarchaeology of Terra Preta: Formation Processes, Cultural Practices and Perceptions of Anthrosols the Upper Xingu Community.” The size of ancient human populations in the Amazon and the extent of their ecological impacts are hotly debated. Central to this debate is dark earth — anthropic soil characterized by darker color, higher organic carbon content, and higher fertility than typical Amazonian upland soils. Archaeological evidence indicates that dark earth formed in association with human occupation, but it is uncertain what practices created dark earth, what determined its spatial extent, and whether humans created it intentionally. The amount of carbon distributed across dark earth sites is largely unknown, adding uncertainty to the potential climate impacts of soil carbon loss due to land-use change and global warming. This research shows similarities between dark earth in ancient and modern contexts and documents contemporary indigenous practices that enrich soil. Interviews with Kuikuro specialists show how they act to intentionally create dark earth for crop cultivation. This combined evidence suggests that ancient Amazonians managed soil to improve fertility and increase crop productivity. These practices also sequestered and stored carbon in the soil for centuries. Our results demonstrate the intentional creation of Amazonian dark earth, highlighting that indigenous knowledge can provide strategies for sustainable rainforest management.