30,000 years of fire history in the Cerrado.

The Cerrado, or Brazilian savanna, is a fire-prone ecosystem whose fire adaptations likely originated in the Miocene, with many plants retaining fire-adapted traits of fire up to the present. It is nowadays one of the most frequently and intensely burned ecosystem on Earth, but little is known about its fire history, from the Miocene to more recent times. We compiled a unique dataset of 12 macro-charcoal records from lacustrine or swamp sediments, covering the last 30,000 years in northern, central, and southeastern Cerrado. Our aim was to examine the relationships between charcoal abundance, vegetation structure, and climate variability. We analyzed charcoal abundance, fuel sources and fire return intervals as a function of vegetation cover (Poaceae frequencies), human activities and climate changes. Results indicate that different fire regimes have occurred over the past 30,000 years, with enhanced biomass burning during maxima of solar radiation and high atmospheric CO2 levels. Under natural fire drivers, overall savanna structure persisted across different fire regimes, although with significant local and regional variability. By linking insolation cycles and atmospheric CO2 to fire dynamics, we show that the Cerrado fire regime has shifted from being primarily climate-driven to increasingly human-driven.