Raised-field agricultural systems in the Neotropics: Past, present and heir implications for sustainable agriculture
The need to reconcile food production, ecosystem services and biodiversity conservation has spurred the search for more sustainable ways of farming. Archaeology offers examples of prehistoric pathways to agricultural intensification that could be rich sources of inspiration for applying ecological engineering in agriculture today. In this presentation, I will briefly summarise the nature of pre-Columbian raised field agriculture. In particular, I will report a 2,150 yr old paleoecological record from a French Guianan coastal savanna that forces reconsideration of how pre-Columbian savanna peoples practiced raised-field agriculture and how the Columbian Encounter impacted these societies and environments. The study shows that pre-Columbian raised-field farmers limited burning to improve agricultural production, contrasting with extensive use of fire in pre-Columbian tropical forest and Central American savanna environments, as well as in present-day savannas. The charcoal record indicates that extensive fires in the seasonally flooded savannas of French Guiana are a post-Columbian phenomenon, postdating the collapse of indigenous populations. The discovery that pre-Columbian farmers practiced fire-free savanna management calls into question the widely held assumption that pre-Columbian Amazonian farmers pervasively used fire to manage and alter ecosystems. More importantly, I will discuss how this land use management offers fresh perspectives on an emerging alternative approach to savanna land use and conservation that can help reduce carbon emissions.
We examine one set of techniques, pre-Columbian raised-field agriculture in wetlands of Mesoamerica and South America. We point to gaps in knowledge at three levels. First, raised-field agriculture was conducted in a wide range of soils and climates. How different systems functioned was likely to have been correspondingly diverse, but this variation is under-appreciated. At the scale of single farms, nutrient dynamics in raised-field systems likely included complexities quite unusual in 'modern' agriculture, owing to the mixture of aerobic and waterlogged compartments, but data are scarce. Second, at the landscape level there is disagreement about whether fallow periods were necessary, and their eventual roles are poorly understood. Current evidence suggests that self-organizing processes in fallows may have increased the sustainability of some raised-field farming systems in unusual ways. Third, the labor-intensive nature of raised-field farming is held to limit its pertinence to today's global problems, but its real labor costs are unknown. Furthermore, achieving sustainable intensive agriculture will require compensating farmers for ecosystem services they provide. Under a socioeconomic regime that does this, raised-field agriculture could have considerable practical application.