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Human-ignited fires result in more extreme fire behavior and ecosystem impacts.

ABSTRACT: California has experienced a rapid increase in burned area over the past several decades. Although fire behavior is known to be closely tied to ecosystem impacts, most analysis of changing fire regimes has focused solely on area burned. Here we present a standardized database of wildfire behavior, including daily fire rate-of-spread and fire radiative power for large, multiday wildfires in California during 2012-2018 using remotely-sensed active fire observations. We observe that human-ignited fires start at locations with lower tree cover and during periods with more extreme fire weather. These characteristics contribute to more explosive growth in the first few days following ignition for human-caused fires as compared to lightning-caused fires. The faster fire spread, in turn, yields a larger ecosystem impact, with tree mortality more than three times higher for fast-moving fires (>1 km day^-1) than for slow moving fires (<0.5 km day^-1). Our analysis shows how human-caused fires can amplify ecosystem impacts and highlights the importance of limiting human-caused fires during period of extreme fire weather for meeting forest conservation targets under scenarios of future change.

SUBMITTER: Hantson S

PROVIDER: S-EPMC9114381 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Human-ignited fires result in more extreme fire behavior and ecosystem impacts.

Hantson Stijn S Andela Niels N Goulden Michael L ML Randerson James T JT

Nature communications 20220517 1

California has experienced a rapid increase in burned area over the past several decades. Although fire behavior is known to be closely tied to ecosystem impacts, most analysis of changing fire regimes has focused solely on area burned. Here we present a standardized database of wildfire behavior, including daily fire rate-of-spread and fire radiative power for large, multiday wildfires in California during 2012-2018 using remotely-sensed active fire observations. We observe that human-ignited f ...[more]

PMID: 35581218

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Project description:Extreme climatic events are among the drivers of recent declines in plant biomass and productivity observed across Arctic ecosystems, known as "Arctic browning." These events can cause landscape-scale vegetation damage and so are likely to have major impacts on ecosystem CO2 balance. However, there is little understanding of the impacts on CO2 fluxes, especially across the growing season. Furthermore, while widespread shoot mortality is commonly observed with browning events, recent observations show that shoot stress responses are also common, and manifest as high levels of persistent anthocyanin pigmentation. Whether or how this response impacts ecosystem CO2 fluxes is not known. To address these research needs, a growing season assessment of browning impacts following frost drought and extreme winter warming (both extreme climatic events) on the key ecosystem CO2 fluxes Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), ecosystem respiration (Reco ) and soil respiration (Rsoil ) was carried out in widespread sub-Arctic dwarf shrub heathland, incorporating both mortality and stress responses. Browning (mortality and stress responses combined) caused considerable site-level reductions in GPP and NEE (of up to 44%), with greatest impacts occurring at early and late season. Furthermore, impacts on CO2 fluxes associated with stress often equalled or exceeded those resulting from vegetation mortality. This demonstrates that extreme events can have major impacts on ecosystem CO2 balance, considerably reducing the carbon sink capacity of the ecosystem, even where vegetation is not killed. Structural Equation Modelling and additional measurements, including decomposition rates and leaf respiration, provided further insight into mechanisms underlying impacts of mortality and stress on CO2 fluxes. The scale of reductions in ecosystem CO2 uptake highlights the need for a process-based understanding of Arctic browning in order to predict how vegetation and CO2 balance will respond to continuing climate change.

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Human-ignited fires result in more extreme fire behavior and ecosystem impacts.

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Human-ignited fires result in more extreme fire behavior and ecosystem impacts.

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