Université Montpellier II and Centre d'Ecologie Fonctionnelle et Evolutive, Unité Mixte de Recherche 5175 Centre National de la Recherche Scientifique, F-34293 Montpellier Cedex 5, France.
Proc Natl Acad Sci U S A. 2010 Apr 27;107(17):7823-8. doi: 10.1073/pnas.0908925107. Epub 2010 Apr 12.
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 follows 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.
在亚马逊地区,前哥伦布时期人类活动的规模和性质目前存在激烈争议。尽管前哥伦布时期的人类在亚马逊地区的一些地方极大地改变了物种和栖息地的分布和丰度,但他们在其他地方的影响却不那么明显。开创性的研究曾提出,他们的影响是否进一步扩大,改变了生态系统的功能,但很少有深入的研究探讨这些改变的弹性背后的机制。我们结合考古学、考古植物学、古生态学、土壤科学、生态学和航空图像,展示了圭亚那沿海地区的前哥伦布时期农民建造了大型的高地农田综合体,在上面种植了玉米、木薯和南瓜等作物。农民通过建造高地农田,在平坦、沼泽的环境中创造了物理和生物地球化学的异质性。当这些田地后来被废弃时,积水基质中排水良好的岛屿镶嵌模式引发了由生态工程师(蚂蚁、白蚁、蚯蚓和木本植物)驱动的自组织过程,这些工程师更倾向于出现在废弃的高地农田上。如今,这些生态工程师产生的反馈维持了这些结构中人类引发的资源集中。工程师生物将物质输送到废弃的高地农田,并改变其土壤的结构和组成,从而降低可侵蚀性。人类与自然共同构建的这些景观中生态系统功能的深刻改变,对理解亚马逊地区的历史和生物多样性具有重要意义。此外,这些景观展示了如何通过将维持生态系统服务和生物多样性的工程设计融入到粮食生产系统中,来提高其可持续性。与亚马逊森林中的人为黑土一样,这些自组织的生态系统说明了前哥伦布时期土地利用的遗产所具有的生态复杂性。