Scarce fire activity in north and north-western Amazonian forests during the last 10,000 years

Background Fire is known to affect forest biodiversity, carbon storage, and public health today; however, comparable fire histories from across forest regions in Amazonia are lacking. Consequently, the degree to which past fires could have preconditioned modern forest resilience to fire remains unknown. Aim We characterised the long-term (multi-millennial) fire history of forests in Amazonia to determine spatial and temporal differences in fire regimes. Methods We collated and standardised all available charcoal data extracted from continuously deposited lake sediments (n = 31) to reconstruct a ca. 10,000-year fire history for: (i) north and north-western, (ii) south-western, and (iii) eastern parts of Amazonia. Results Charcoal was found across Amazonia, but it was less abundant in the north and north-western regions. Regionally distinct periods of elevated charcoal deposition were identified at between ca. 4000 and 1500 (eastern), 3000-1000 (south-western) and 2500-2000 (north and north-western) years ago. Conclusions Forests in eastern and south-western Amazonia have been exposed to fire activity over recent millennia, while the forests in north and north-western Amazonia have grown under conditions largely free of fire activity. Consequently, we hypothesise that the forests in eastern and south-western Amazonia are preconditioned to be relatively more resilient to the threat of increased modern fire activity.