Coherent signature of warming-induced extreme sub-continental boreal wildfire activity 4800 and 1100 years BP

Abstract

Climate changes are expected to progressively increase extreme wildfire frequency in forests. Finding past analogs for periods of extreme biomass burning would provide valuable insights regarding what the effects of warming might be for tree species distribution, ecosystem integrity, atmospheric greenhouse gas balance, and human safety. Here, we used a network of 42 lake-sediment charcoal records across a ∼2000 km transect in eastern boreal North America to infer widespread periods of wildfire activity in association with past climate conditions. The reconstructed fluctuations in biomass burning are broadly consistent with variations in ethane concentration in Greenland polar ice cores. Biomass burning fluctuations also significantly co-varied with Greenland temperatures estimated from ice cores, at least for the past 6000 years. Our retrospective analysis of past fire activity allowed us to identify two fire periods centered around 4800 and 1100 BP, coinciding with large-scale warming in northern latitudes and having respectively affected an estimated ∼71% and ∼57% of the study area. These two periods co-occurred with widespread decreases in mean fire-return intervals. The two periods are likely the best analogs for what could be anticipated in terms of impacts of fire on ecosystem services provided by these forests in coming decades.

Impacts of Climate Change on Wildfires in Central Asia

“…Wildfires are a dominant disturbance in most forests and are strongly influenced by climate [1]. Climate warming has recently caused changes in the fire regime in the Northern Hemisphere [2], which has experienced extreme wildfire seasons and fire frequency increases in forests. Notably, high-intensity fires have occurred in summer in some regions.…”

The 2023 wildfire season in Québec: an overview of extreme conditions, impacts, lessons learned and considerations for the future

“…Over the last centuries, variations in drought severity and frequency have significantly influenced fire regimes in Québec. Research shows that fire activity is closely linked to temperature, precipitation, vegetation, and human activities, highlighting the complex relationship between climate change and fires (Carcaillet et al 2001; Remy et al 2017; Girardin et al 2019). To understand the 2023 wildfires, it is essential to differentiate between the wildfire histories of the Intensive Protection Zone and Northern Protection Zone, as historical fire drivers differed between these zones.…”

The North American tree‐ring fire‐scar network

“…Insights provided by the fire-scar network have applicability primarily across the sampled range of forest types and climate spaces it represents. This calls for research efforts to fill data gaps (e.g., sites in warmer or wetter climates), but acknowledges that some regions and forest types may not contain tree-ring fire-scar records, necessitating other approaches such as paleocharcoal (Girardin et al, 2019), forest age structure-derived fire history (Drobyshev et al, 2017;Johnson & Larsen, 1991;Van Wagner, 1978), or the use of precisely dateable anatomical indicators of fire exposure (Arbellay et al, F I G U R E 8 (a-n) Climate space of forests, the North American fire-scar network (NAFSN) sites, and modern fires in terms of mean annual precipitation (MAP; square root transformed) and mean annual temperature (MAT) by ecoregion. Forests: Density estimates of the forested climate space were derived using 2D kernel density estimation and scaled from 0.0 to 1.0 (blue to cyan), with 1 corresponding to the highest densities.…”

“…Insights provided by the fire‐scar network have applicability primarily across the sampled range of forest types and climate spaces it represents. This calls for research efforts to fill data gaps (e.g., sites in warmer or wetter climates), but acknowledges that some regions and forest types may not contain tree‐ring fire‐scar records, necessitating other approaches such as paleo‐charcoal (Girardin et al, 2019), forest age structure‐derived fire history (Drobyshev et al, 2017; Johnson & Larsen, 1991; Van Wagner, 1978), or the use of precisely dateable anatomical indicators of fire exposure (Arbellay et al, 2014a, 2014b). We also note that we characterized the NAFSN in the context of contemporary climate space, whereas historical fires may have burned under different climate conditions centuries ago.…”