History of Amazonian Savannas in the Last 10,000 Years

There is no arguing about the occurrence of savannas in the middle of the Amazon forest anymore. However, several questions still remain unresolved, such as: How and when were they formed? Do they all share the same origins? As an attempt to address some of these complicated issues, we tried to investigate how climate and human activity may have influenced areas of disjoint savannas within Brazilian Amazonia. Fossil pollen, charcoal, and radiocarbon records of 6 lakes were used to provide a regional palaeoecological history of northeastern Amazonia in the Holocene. The analyses performed on these sediment cores allowed us to infer and date changes in the environment, vegetation, hydrology and sedimentation, and also to recognize human occupation near the lakes in the last 7,000 years. Although each individual record indicated local variation, all the studied lakes were Holocene in age, and exhibited rising water levels until ca. 6500-5300 years BP. We were also able to identify the establishment of savannas in Eastern Amazonia (Amapá), a strong signal of human occupation in central Amazonia (Prainha), and relatively stable savanna vegetation in the Northernmost site (Roraima).