The extent to which biomass burning declined across the Americas after ca. AD 1500, and its cause, is a topic of considerable debate. To investigate whether climate or human population collapse was responsible for changes in biomass burning over 300 sedimentary charcoal records from the Americas were examined to produce continental- and regional-scale summaries of late-Holocene fire activity. The Hyde 3.1 global population data and a network of paleoclimate proxies from the Americas were used to explore the influence of climate versus population on regional fire activity.
A widespread post-AD 1500 decrease in biomass burning is evident, not only in the tropics, as previously assumed, but also in middle and high latitudes. The minimum in biomass burning for all of the Americas occurred between AD 1600 and 1750, although there are regional differences in the timing and amplitude of this downturn. Comparisons with paleoclimate records and pre-Columbian population estimates suggest long-term trends in climate, culminating in the Little Ice Age cooling, were underway several centuries before the arrival of European diseases and demographic collapse in the Americas. This analysis suggests climate rather than population collapse is a more parsimonious explanation for the 17th century decline in biomass burning.