The impact of fire on the Late Paleozoic Earth system

Abstract

Analyses of bulk petrographic data indicate that during the Late Paleozoic wildfires were more prevalent than at present. We propose that the development of fire systems through this interval was controlled predominantly by the elevated atmospheric oxygen concentration (p(O2)) that mass balance models predict prevailed. At higher levels of p(O2), increased fire activity would have rendered vegetation with high-moisture contents more susceptible to ignition and would have facilitated continued combustion. We argue that coal petrographic data indicate that p(O2) rather than global temperatures or climate, resulted in the increased levels of wildfire activity observed during the Late Paleozoic and can, therefore, be used to predict it. These findings are based upon analyses of charcoal volumes in multiple coals distributed across the globe and deposited during this time period, and that were then compared with similarly diverse modern peats and Cenozoic lignites and coals. Herein, we examine the environmental and ecological factors that would have impacted fire activity and we conclude that of these factors p(O2) played the largest role in promoting fires in Late Paleozoic peat-forming environments and, by inference, ecosystems generally, when compared with their prevalence in the modern world.

Earliest land plants created modern levels of atmospheric oxygen

“…The early charcoal record (Table S1) was compiled from the literature (11,12,28, using existing compilations (12,(44)(45)(46)(47) and checking them where possible against the original sources. This process involved some reconciling of disparate results between existing compilations and revision of some erroneous quoted values.…”

Evidence of widespread wildfires in a coal seam from the middle Permian of the North China Basin

“…270 Ma) (Berner, 2006(Berner, , 2009. These fluctuations are suspected of having a dramatic effect on the development of fire systems (Belcher and McElwain, 2008;Shi and Waterhouse, 2010;Glasspool et al, 2015). According to Belcher et al (2010b), Earth's highest fire frequencies under current levels of O 2 are mainly in equatorial dry areas and seasonally dry climates; if O 2 significantly increased >25%, even swamp and wet areas would burn, so that fire frequencies would be increased in both tropical rainforest and arctic tundra.…”

“…2F) (Bergman et al, 2004;Berner, 2006). The gradual decrease of O 2 could have consumed by the occurrence of global wildfires (Singh and Shukla, 2004;Jasper et al, 2013;Manfroi et al, 2015;Kauffmann et al, 2016), also affecting the North China Basin (Scott and Glasspool, 2006;Glasspool et al, 2015). Experimental data also provide the following observations on O 2 levels and fire in the fossil record: fire activity would be greatly suppressed below 18.5% O 2 , and entirely stopped below 16% O 2 (Belcher et al, 2010b); between 18% and 23% fire occurrences would have been similar to those under the present atmospheric level (PAL) of 21% (Pyne et al, 1996); at a level of 25% O 2 in the atmosphere, fires would have been widespread (Wildman et al, 2004); and fire activity would have been globally distributed at O 2 levels over 25% (Belcher et al, 2010b) or levels of 30% (Wildman et al, 2004).…”

“…According to Belcher et al (2010b), Earth's highest fire frequencies under current levels of O 2 are mainly in equatorial dry areas and seasonally dry climates; if O 2 significantly increased >25%, even swamp and wet areas would burn, so that fire frequencies would be increased in both tropical rainforest and arctic tundra. According to an inertinite ratio-O 2 level calculation curve (Glasspool et al, 2015), O 2 levels reached ~27% in the middle Permian in the North China Basin; therefore, O 2 levels of 27% could have caused widespread wildfires in the basin. The O 2 levels gradually decreased from Widespread wildfire from the middle Permian coal of the North China Basin | RESEARCH 270 to 260 Ma, and then dramatically decreased from 260 to 250 Ma (Fig.…”

“…In the middle Permian, global O 2 levels should have been >27% (Berner, 2006(Berner, , 2009, and caused global wildfire; therefore, wildfires in the North China Basin might have been only a part of the global wildfires during that period (Wang and Chen, 2001;Yan et al, 2016). Data from a total of 2989 coal samples collected worldwide were summarized by Glasspool et al (2015). Their inertinite contents were calculated and divided into different groups according to the coal age (Table 3).…”