Domestication of amazonian forests
The idea that Amazonian forests have been largely untouched by humans has fascinated naturalists, policy makers, the media, and natural and social scientists worldwide. For many decades, ecological studies overlooked the influence of past peoples in modern forests. However, humans arrived in the Amazon basin at least 13,000 years Before Present (BP) and populations expanded strongly around 2,500 years BP. Evidence of past human activities has been found in extensive areas previously considered pristine. Anthropogenic soils (Amazonian Dark Earths - ADE) and human-made earthworks found across the basin are examples of the landscapes domesticated by pre-Columbian peoples and evidence of large societies with considerable capacity for modifying the environment. Cultivation and management of Amazonian flora by past societies may have significantly contributed to the ecological patterns we see today. These findings stimulated an academic debate about the pristineness versus domestication of Amazonian forests. Although most scientists agree that human impacts were spatially heterogeneous across the basin, the scale of past human influences in Amazonian forests remains controversial. A more realistic and broadscale view is required (Chapter 1). In my thesis, I integrated data from different disciplines in the social and natural sciences to generate the first broad-scale assessment of the effects of long-term human influences in modern Amazonian forests and how these legacies are maintained by local management practices. I studied the Amazon forest as a mosaic of patches domesticated to different degrees by human-nature interactions. To estimate the influence of past people on modern forests, I first compared the density of sedentary pre-Columbian occupation sites with ADE along some stretches of major white-water rivers and their black or clear-water tributaries that have been sampled by archaeologists. I counted the number of archaeological sites along 12-km sections for both river orders (major and tributary) and found the same density of sites along both orders, showing that archaeological sites are widespread across tributary rivers of the Central Amazon basin (Chapter 2). This result suggests that the influence of past societies in Amazonian landscapes is more extensive than previously imagined and deserves further investigation. To unravel the effects of long-term human actions at the basin-wide scale, we investigated the relationship between the richness and abundance of 85 domesticated plant species found in Amazonian forests and the distribution of known archaeological sites (Chapter 3). We focused on domesticated species because they are known to have been propagated and selected by peoples in Amazonia and elsewhere in the Americas for food or other uses for a long time. I correlated data from more than 1,000 floristic inventories of the Amazon Tree Diversity Network (ATDN) with a map of more than 3,000 archaeological sites across different Amazonian geological regions compiled by the AmazonArch Network. Our analysis also incorporated environmental data to distinguish the relative importance of environmental conditions from past human factors on modern plant communities. We found that domesticated species were five times more likely to be common in floristic inventories than nondomesticated species and sometimes more abundant far from the places where they were domesticated, suggesting past human dispersal. The richness and abundance of these domesticated species increase with the proximity to archaeological sites and in areas with poorly drained soils and higher rainfall seasonality. Our results show that plant communities in Amazonia are structured by both natural and cultural processes, and refute the idea that these forests are largely untouched by humans. To understand the relative contribution of past and recent human activities in shaping these current floristic patterns, we expanded our previous analyses to incorporate the influence of current activities (Chapter 4). We found that old-growth forests were transformed by both past and current peoples, but we showed that the effects of recent activities have a smaller role when compared to the persistent effects of pre-Columbian activities on forest composition. Overall, these new analyses strengthened the importance of ancient peoples in explaining the richness and abundance of domesticated species across Amazonia.
| Main Authors: | , , , , |
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| Format: | Texto biblioteca |
| Language: | eng |
| Published: |
Wageningen, The Netherlands Wageningen University. Instituto National de Pesquisas da Amazônia
2018
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| Subjects: | Ordenación forestal, Actividades antropogénicas, Bosques, Efecto de los seres humanos sobre la naturaleza, |
| Online Access: | http://library.wur.nl/WebQuery/wurpubs/538191 |
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