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New research is dismantling the long-standing myth of the "pristine" Amazon. A reconstruction of 10,000 years of Amazonian pyrogeography, based on 1,361 radiocarbon (¹⁴C) dates across 303 sites - including soil charcoal and burned archaeological material - shows that fire in the rainforest is almost exclusively a human-driven phenomenon, not a natural one. Over the last two millennia, human-ignited fire has driven vegetation change on a scale comparable to major climatic shifts, such as deglaciation or the extinction of Pleistocene megafauna. The research has been published in the open-access, peer-reviewed Frontiers of Biogeography journal.
The human spark
Amazonian fires rarely, if ever, ignite without human input. In the pre-human evolutionary history of these wet forests, fire was an exceptional rarity.
Glacial-aged paleoecological reconstructions from sites like the Hill of Six Lakes in Brazil and the Serra Sul dos Carajás reveal that charcoal was either entirely absent or present in only minuscule amounts before human arrival. Even more striking, the Campo Libre sediment core on the Andean slopes of Ecuador showed a total absence of fire for 30,000 years, ending only when humans appeared on the landscape around 4,500 years ago.
