How natural are Amazonian forests? Fire as a transformative process

Background/Question/Methods: The naturalness of Amazonia has been hotly contested by academics with different world views. Scientists studying ecological processes have often labeled old-growth forests as either ‘primary’ or ‘pristine’, while anthropologists and archaeologists inevitably emphasize anthropogenic influences and consider much of Amazonia to be an ‘anthropogenic forest’ or ‘cultural parkland’. I explore this debate using data collected following recent wildfires in Amazonian forests.

Results/Conclusions: In some regions these wildfires cause very high levels of tree mortality (up to 50% of trees >10cm in DBH) and an almost complete turnover in the species composition of regenerating trees. However, other Amazonian forests appear to be more resilient, with tree mortality as low as 20%, suggesting a longer evolutionary history of fire in these systems. Furthermore, evidence suggests that some forests that have been considered pristine are actually recovering from understorey fires. Finally, I will demonstrate that ecologists and anthropologists could have a more constructive debate regarding the naturalness of Amazonia by adopting better and more precise definitions of disturbed forests.