PreColumbian Agricultural Impacts in the Amazon

Pre-Columbian agricultural landscapes, ecosystem engineers, and self-organized patchiness in Amazonia

1. Doyle McKey (a,1)
2. Stéphen Rostain (b)
3. José Iriarte (c)
4. Bruno Glaser (d,2)
5. Jago Jonathan Birk (d)
6. Irene Holst (e)
7. Delphine Renard (a)


a. Université Montpellier II and Centre d'Ecologie Fonctionnelle et Evolutive, Unité Mixte de Recherche (UMR) 5175 Centre National de la Recherche Scientifique (CNRS), F-34293 Montpellier Cedex 5, France;

b. Archéologie des Amériques, UMR 8096 CNRS, F-92323 Nanterre, France;

c. Department of Archaeology, School of Geography, Archaeology, and Earth Resources, University of Exeter, Exeter EX4 4QE, United Kingdom;

d. Department of Soil Physics, University of Bayreuth, Bayreuth D-95447 Germany; and

e. Smithsonian Tropical Research Institute, Apartado Postal 0843 -03092, Balboa, Republic of Panama

1. To whom correspondence should be addressed. E-mail: doyle.mckey@cefe.cnrs.fr.

2. Present address: Terrestrial Biogeochemistry, Martin-Luther-University Halle-Wittenberg, 06108 Halle, Germany.

Abstract:

The scale and nature of pre-Columbian human impacts in Amazonia are currently hotly debated. Whereas pre-Columbian people dramatically changed the distribution and abundance of species and habitats in some parts of Amazonia, their impact in other parts is less clear. Pioneer research asked whether their effects reached even further, changing how ecosystems function, but few in-depth studies have examined mechanisms underpinning the resilience of these modifications. Combining archeology, archeobotany, paleoecology, soil science, ecology, and aerial imagery, we show that pre-Columbian farmers of the Guianas coast constructed large raised-field complexes, growing on them crops including maize, manioc, and squash. Farmers created physical and biogeochemical heterogeneity in flat, marshy environments by constructing raised fields. When these fields were later abandoned, the mosaic of well-drained islands in the flooded matrix set in motion self-organizing processes driven by ecosystem engineers (ants, termites, earthworms, and woody plants) that occur preferentially on abandoned raised fields. Today, feedbacks generated by these ecosystem engineers maintain the human-initiated concentration of resources in these structures. Engineer organisms transport materials to abandoned raised fields and modify the structure and composition of their soils, reducing erodibility. The profound alteration of ecosystem functioning in these landscapes coconstructed by humans and nature has important implications for understanding Amazonian history and biodiversity. Furthermore, these landscapes show how sustainability of food-production systems can be enhanced by engineering into them fallows that maintain ecosystem services and biodiversity. Like anthropogenic dark earths in forested Amazonia, these self-organizing ecosystems illustrate the ecological complexity of the legacy of pre-Columbian land use.

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