Abstract
Anthropogenic climate change—combined with increased human-caused ignitions—is leading to increased wildfire frequency, carbon dioxide emissions, and refractory black carbon (rBC) aerosol emissions. This is particularly evident in the Amazon rainforest, where fire activity has been complicated by the synchronicity of natural and anthropogenic drivers of ecological change, coupled with spatial and temporal heterogeneity in past and present land use. One approach to elucidating these factors is through long-term regional fire histories. Using a novel method for rBC determinations, we measured an approximately 3500-year sediment core record from Lake Caranã in the eastern Amazon for rBC influx, a proxy of biomass burning and fossil fuel combustion. Through comparisons with previously published records from Lake Caranã and regional evidence, we distinguished between local and regional rBC emission sources demonstrating increased local emissions of rBC from ~1250 to 500 calendar years before present (cal yr BP), coinciding with increased local-scale fire management during the apex of pre-Columbian activity. This was followed by a regional decline in biomass burning coincident with European contact, pre-Columbian population decline, and regional fire suppression associated with the rubber boom (1850–1910 CE), supporting the minimal influence of climate on regional burning at this time. During the past century, rBC influx has rapidly increased. Our results can serve to validate rBC modeling results, aiding with future predictions of rBC emissions and associated impacts to the climate system.
Highlights
Anthropogenic increases in carbon dioxide (CO2 ) emissions, combined with an increase in human-caused ignitions, are leading to more severe fire seasons and increasing the frequency of wildfires [1]
Previous research indicates firemanagement management practices were the dominant driver of fire activity during the late Holocene at Lake Caranã [41,42]
Our results demonstrate the applicability of this new method for reconstructing refractory black carbon (rBC) in low latitude sites an area of few long-term studies [12,15]
Summary
Anthropogenic increases in carbon dioxide (CO2 ) emissions, combined with an increase in human-caused ignitions, are leading to more severe fire seasons and increasing the frequency of wildfires [1]. This is evident in the Amazon rainforest, the world’s largest terrestrial carbon sink [2]. Recent work has shown that rBC aerosols have an important role in climate by directly changing Earth’s radiation budget [5] and indirectly by changing cloud formation and reducing albedo [6,7]. Global rBC emissions have increased throughout the 20th century
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