Pre-Columbian agriculture in the Bolivian Lowlands: Construction history and management of raised fields in Bermeo

• Pre-Columbian raised fields in the Bolvian Lowlands
• This study provides a novel model for the pre-Columbian management of raised fields.
• OSL dating shows that the raised fields were use since as early as AD 570–770.
• Data suggests that raised fields were constructed during individual episodes.
• We suggest that raised fields were constructed to overcome periods severe flooding.

Recent archaeological research suggests that some parts of the Amazon Basin were significantly modified by pre-Columbian populations. One of the most impressive examples of such transformations is the raised fields of south-western Amazonia, in the Llanos de Moxos in the Bolivian Lowlands. Despite a growing interest in raised field agriculture, due to the important role it seems to have played in the development of pre-Columbian complex societies, very few field-based investigations have been performed in the Amazon Basin. As a result, there is limited knowledge of how these fields were constructed, managed and within which time-frame they were in use.This study provides a new interpretation of how pre-Columbian raised fields were managed and a chronological sequence of their utilisation and eventual abandonment. Fieldwork was carried out in the indigenous community of Bermeo, in the vicinity of San Ignacio de Moxos, where some of the best preserved fields in the Llanos Moxos are found. Magnetic susceptibility and the geochemistry of the sediments, combined with radiocarbon and optically stimulated luminescence dating, show that the raised fields were in intermittent use since as early as AD 570–770. The original surface on which the fields were built and distinct periods of construction and use have been identified. The data suggests that raised fields were built during a few separate construction events, probably linked to periods of more frequent and severe floods. The study challenges the most widely accepted theory that suggests that pre-Columbians were able to cultivate these fields on a continuous basis by transferring nutrient-rich sediments from the canals to the fields. We conclude that pre-Columbians built raised fields to overcome periods of increased flooding, with the main objective of improving drainage.