Neotropical human–landscape interactions, fire, and atmospheric CO2 during European conquest

Abstract

Neotropical biomass burning reconstructions synthesized from soil and sedimentary charcoal records indicate a period of reduced biomass burning sustained for several centuries after ~500 cal. yr BP. Proxy records of solar irradiance, El Niño events, temperature, and precipitation document regionally variable climate-related trends that do not account for the uniform reduction in burning across the Neotropics. Decreased human ignition resulting from pandemic-induced mortality offers an alternative, geographically comprehensive explanation. In addition, natural (solar-volcanic) factors can explain only ~1.3 ppm out of the rapid 6–10 ppm CO2 decrease between ad 1525 and the early 1600s. Reforestation following land abandonment due to population collapse has the potential to account for the rest of this CO2 decline, and variations in the 13C/12C of atmospheric CO2 and CH4 are consistent with both a major reduction in Neotropical landscape management by fire and massive reforestation. Our findings are demonstrative of the scale at which pre-industrial human activities influenced Earth’s atmospheric greenhouse gas budget.