Amazonia rainforest fires: A lacustrine record of 7000 years

Although human influence dominates present-day Amazonian rainforest fires, old charcoal fragments, buried in the soils or in lacustrine sediments, confirm that fire has played a major role in the history of Amazonian forests. These fires may have influenced the present-day diversity and structure of the rainforest and if these fire-favorable events of the past reoccur there may be drastic consequences for the future of the Amazonian forests. Detailed studies of Carajas lake sediments permit identification of these past fire events, through microscopic observations of small charcoal fragments. They also permit, through radiocarbon dating, a better definition of their timing and make it possible to relate them to past paleo-environmental and paleoclimatic conditions. The paleodata indicate that fire events were concomitant with short dry climate episodes whose frequency of occurrences has varied during the last 7000 years. These dry events may be related to past climate conditions observed in different regions of tropical South America.