This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: New research is dismantling the longstanding 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 Frontiers of Biogeography. Amazonian fires rarely, if ever, ignite without human input.
In the prehuman evolutionary history of these wet forests, fire was an exceptional rarity. Glacial-age 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 strikingly, 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.
In their paper, the researchers describe the arrival of humans as the introduction of fire to a "naive landscape." Because Amazonian plants are evolutionarily fire-sensitive, the introduction of regular burning by a fire-using species fundamentally altered a system that had been stable since the late Pleistocene. By compiling and analyzing 1,361 radiocarbon-dated charcoal fragments and archaeological materials, researchers mapped a history of human-driven fire across Amazonia that unfolded over three phases of the Holocene. Between 10,000 and 6,000 years ago, fires were highly restricted, occurring primarily within the basin's peripheral areas and along the main channel of the Amazon River.
This localized footprint shifted dramatically between 6,000 and 4,000 years ago, as the geographic spread of fire and occupation sites accelerated sharply across most regions—a development that coincided with the onset of early maize cultivation in northwestern and southwestern Amazonia. Finally, between 3,000 and 2,000 years ago, fire reached the deep interior of the basin. Though central Amazonia had remained a relatively fire-free refuge for thousands of years while the periphery burned, it was ultimately transformed as expanding human influence and fire use reached the very heart of the forest.
This human-driven fire history is marked by a dramatic, two-phase decline over the last 700 years. First, fire frequency decreased 600 to 700 years ago, supporting the "early abandonment" of lands several centuries before European arrival. Physical evidence from lake sediments shows a significant "pollen surge" during this window, signaling massive reforestation and a major pre-Columbian shift in land use or site abandonment.
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