Anthropogenic Soils of the Amazon: Origins, Extent, and Implications for Sustainable Tropical Agriculture

Many tropical soils are marginal for agriculture because they are nutrient-poor and contain little organic carbon. Yet archaeological evidence shows that some tropical regions supported thriving societies well before the advent of modern agricultural techniques. Between 500 and ~8,700 years ago, pre-Columbian societies in the Amazon Basin created and cultivated extensive deposits of rich soils known as anthropogenic dark earth (ADE) or terra preta (“dark earth” in Portuguese). ADEs are so fertile that they are still farmed (and destructively mined) today, and modern researchers are attempting to reproduce them as part of a strategy for sustainable tropical agriculture and carbon sequestration.

Although the origins and extent of ADEs remain unclear, their modern relevance is very clear: If we can determine how ancient people engineered the landscape to create a productive and sustainable agricultural tradition in a marginal tropical environment, we will be able to conserve the soil resources they created and adapt their technology to guide agricultural development in other tropical regions. This PI team will pursue a multi-disciplinary pilot study that will draw on geoscience, archaeology, materials engineering, and machine learning to:

(1) Develop a predictive model of Amazonian ADE location and extent to aid the discovery and conservation of ADE sites; and

(2) Clarify the “recipe” for creating ADEs in terms of landscape characteristics, including the role of Amazonian rivers, as well as soil materials.

The team anticipates that this unique ability to combine geospatial and materials analysis techniques with archaeological and cultural expertise will allow us to understand how the evolving rivers of the Amazon shaped ADE formation and generate insights that will help inform agricultural practices in tropical developing nations.