Spatial and temporal expansion of global wildland fire activity in response to climate change

Abstract

Global warming is expected to alter wildfire potential and fire season severity, but the magnitude and location of change is still unclear. Here, we show that climate largely determines present fire-prone regions and their fire season. We categorize these regions according to the climatic characteristics of their fire season into four classes, within general Boreal, Temperate, Tropical and Arid climate zones. Based on climate model projections, we assess the modification of the fire-prone regions in extent and fire season length at the end of the 21st century. We find that due to global warming, the global area with frequent fire-prone conditions would increase by 29%, mostly in Boreal (+111%) and Temperate (+25%) zones, where there may also be a significant lengthening of the potential fire season. Our estimates of the global expansion of fire-prone areas highlight the large but uneven impact of a warming climate on Earth's environment.

Fig. 1. Burned area observations and climate drivers.

a 1996–2016 maximum annual burned area (BA_max) and monthly burned area time series for selected regions. b Average monthly precipitation percentage from the annual total for the fire season (PP_FS). c Average monthly temperature anomaly from the annual mean for the fire season (TA_FS).

Fig. 2. Fire-prone region classification.

a With observed burned area data as a reference: not classified (NC, white) and misclassified (C, black) areas with BA_max = 0 ha, unclassified (NC, grey) and classified (Tr-ds, Ar-fl, Te-dhs and Bo-hs) areas with BA_max > 0 ha. Each class is subdivided into three subcategories depending on the recurrence of the fire-prone conditions: recurrent (r), occasional (o) and infrequent (i). b Present (1996–2016) fire-prone climatic regions. c Future (2070–2099) fire-prone climatic regions with shaded grey representing a <75% confidence percentage, estimated as the percentage of CMIP5 Global Circulation Models (GCMs) agreeing on the result.

Fig. 3. Potential fire season.

a Future minus present potential fire season length (PFSL) difference in months (ΔPFSL). b Present potential fire season. c Future potential fire season.

Fig. 4. Fire-prone years.

a Future minus a present number of years with at least one month classified as fire-prone per decade (ΔFPY). b Present fire-prone years per decade. c Future fire-prone years per decade.