Raised fields in the Bolivian Amazonia: a prehistoric green revolution or a flood risk mitigation strategy?

摘要

The Llanos de Moxos (LM), Beni, Bolivia, with its impressive number of pre-Columbian earthworks, is an ideal region for studying past human-environment interactions in the Amazonia. Agricultural raised fields are among the most striking of those earthworks. They can offer us valuable information about the region's agricultural carrying capacity and the nature and extent of human occupation in pre-Columbian times and, therefore, help adopt better informed conservation and development strategies for Amazonia in the future. However, before tackling these issues we need to further our understanding of why pre-Columbian raised fields were built and how they were managed in the past. Published data on raised fields in the LM is contrasted with new data gathered from field and remote sensing images. Raised fields have been analysed in relation to the hydrology, soil, topography and paleoclimate of the areas where they are found. In light of this new data we believe that there are grounds to question the current model that suggests raised field agriculture provided high yields without the need of fallow periods, representing a kind of pre-Columbian green revolution. Our alternative proposal suggests that raised field agriculture allowed pre-Columbian peoples to mitigate the risk of more intense and frequent flooding than is experienced today in the LM. We show that raised fields were built only in those areas where there were no alternatives, which do not coincide with those areas where pre-Columbian societies seem to have flourished and reached high levels of social complexity.