A ONE THOUSAND YEAR PALEOCLIMATE RECORD OF WILDFIRE ACTIVITY IN THE NORTHEASTERN UNITED STATES

Future impacts from climate change can be better understood by placing modern trends into perspective through extension of the short instrumental records of climate variability. This is especially true for extreme climatic events such as wildfires. Associations between fire frequency and climate variability have been shown to exist¹, suggesting that future climate change will have a significant effect on wildfire activity. In the Northeastern United States (NEUS), wildfires play an important, albeit rare, role as a disturbance mechanism in dominant ecosystems throughout the region. Fully understanding the natural mechanisms that control fire occurrence and frequencies requires longer-term and continuous records, but presently little is known about the impacts of wildfire regimes in the region prior to human disturbance and anthropogenic climate change.

In this study, a lacustrine record from Basin Pond, Fayette, Maine, USA, is analyzed to reconstruct fire history at sub-decadal resolution over the past 1,000 years. Basin Pond sediment is preserved well enough to produce distinguishable laminations (varves), allowing for an annually- resolved age-to-depth model to be constructed. Using a multi-proxy approach, including organic biomarker analysis of polycyclic aromatic hydrocarbons (PAHs) and macrofossil charcoal counts, a long-term fire history was reconstructed. To distinguish between combustion sources (e.g., biomass burning vs. anthropogenic combustion practices), ratios of PAHs (retene to chrysene) were utilized^2,3. Peaks in PAH abundances were found to occur at times of known large-scale regional wildfire events occurring in the historical period. PAH abundances and charcoal counts are currently being examined from times prior to European settlement to determine if this multi-proxy approach is a promising method for analyzing past wildfire history and frequency at the local and regional scale in the NEUS.

1. A.L. Westerling et al. 2006, Science 313, 940; DOI: 10.1126/science.1128834
2. Yan et al. 2005, Environ. Sci. Technol. 39, 7012-7019.
3. Kuo et al. 2011, Environ. Pollution 159, 983-990.