What the past can say about the present and future of fire

Abstract

Wildfires are an integral part of most terrestrial ecosystems. Paleofire records composed of charcoal, soot, and other combustion products deposited in lake and marine sediments, soils, and ice provide a record of the varying importance of fire over time on every continent. This study reviews paleofire research to identify lessons about the nature of fire on Earth and how its past variability is relevant to modern environmental challenges. Four lessons are identified. First, fire is highly sensitive to climate change, and specifically to temperature changes. As long as there is abundant, dry fuel, we can expect that in a warming climate, fires will continue to grow unusually large, severe, and uncontrollable in fire-prone environments. Second, a better understanding of “slow” (interannual to multidecadal) socioecological processes is essential for predicting future wildfire and carbon emissions. Third, current patterns of burning, which are very low in some areas and very high in others—are often unprecedented in the context of the Holocene. Taken together, these insights point to a fourth lesson—that current changes in wildfire dynamics provide an opportunity for paleoecologists to engage the public and help them understand the potential consequences of anthropogenic climate change.

Emerging palaeoecological frameworks for elucidating plant dynamics in response to fire and other disturbance

“…Palaeorecords offer valuable data for examining the role of fire disturbance as a pivotal agent in driving plant community dynamics over temporal scales that allow us to contextualize ongoing and future change (e.g., Marlon, 2020;Whitlock et al, 2003). This is especially timely, because immense fires in the Pacific Northwest of the USA (Halofsky et al, 2020;Higuera & Abatzoglou, 2021), Australian mega forest fires (Boer et al, 2020) and reports of substantial carbon loss from recent Arctic wildfires (Mack et al, 2011;Natali et al, 2021;Walker et al, 2019) have captured the interest not only of scientists but also of a concerned public.…”

Modeled dispersal patterns for wood and grass charcoal are different: Implications for paleofire reconstruction

“…This interplay between fire and vegetation in the Earth System is intrinsic and spans broad temporal scales (Bowman et al, 2009; Scott, 2000). Although historical data such as recorded observations and satellite imagery can characterize short-term fire-vegetation relationships, long-term archives of fire and vegetation are needed to resolve these relationships on time scales exceeding observational records (Marlon, 2020; Rehn et al, 2021; Vachula et al, 2019; Whitlock and Larsen, 2002). Sedimentary charcoal records are among the most ubiquitous paleofire archives (Hawthorne et al, 2018; Power et al, 2008; Remy et al, 2018) and have provided unique insight into the dynamic relationships between fire, climate, vegetation, and humans (Marlon, 2020; Whitlock et al, 2010).…”

“…Although historical data such as recorded observations and satellite imagery can characterize short-term fire-vegetation relationships, long-term archives of fire and vegetation are needed to resolve these relationships on time scales exceeding observational records (Marlon, 2020; Rehn et al, 2021; Vachula et al, 2019; Whitlock and Larsen, 2002). Sedimentary charcoal records are among the most ubiquitous paleofire archives (Hawthorne et al, 2018; Power et al, 2008; Remy et al, 2018) and have provided unique insight into the dynamic relationships between fire, climate, vegetation, and humans (Marlon, 2020; Whitlock et al, 2010). Despite the continuous development of paleofire research, many uncertainties remain regarding the interpretation and controls of paleofire archives and proxies (Hennebelle et al, 2020; Rehn et al, 2022; Vachula, 2021; Vachula and Cheung, 2021).…”

On the scaling and standardization of charcoal data in paleofire reconstructions

“…A single fire can radically alter the relative abundances of Amazonian rainforest trees, and systems that have burned two or three times within a decade resulted Frontiers of Biogeography 2021, 13.1, e49431 © the authors, CC-BY 4.0 license 2 in an almost complete species turnover and incipient savannization (Barlow & Peres 2008). Local variability in fuel availability, human population density (reflecting potential ignition sources), and droughts would all create a spatial and temporal mosaic of fire effects (e.g., Marlon 2020). Thus, quantifying the spatial and temporal patterns of past fires (hereafter paleofires) is particularly important for understanding modern biogeographic patterns and local scale ecological processes in tropical forests.…”