Editing IPCC:AR6/WGIII/Chapter-7 (section)

==== 7.3.1.4 Fire Regime Changes ====

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Wildland fires account for approximately 70% of the global biomass burned annually ( [[#van%20der%20Werf--2017|van der Werf et al. 2017]] ) and constitute a large global source of atmospheric trace gases and aerosols ( [[#Gunsch--2018|Gunsch et al. 2018]] ) (IPCC WGI AR6). Although fires are part of the natural system, the frequency of fires has increased in many areas, exacerbated by decreases in precipitation, including in many regions with humid and temperate forests that rarely experience large-scale fires naturally. Natural and human-ignited fires affect all major biomes, from peatlands through shrublands to tropical and boreal forests, altering ecosystem structure and functioning ( [[#Argañaraz--2015|Argañaraz et al. 2015]] ; [[#Nunes--2016|Nunes et al. 2016]] ; [[#Remy--2017|Remy et al. 2017]] ; [[#Mancini--2018|Mancini et al. 2018]] ; [[#Aragão--2018|Aragão et al. 2018]] ; [[#Engel--2019|Engel et al. 2019]] ; [[#Rodríguez%20Vásquez--2021|Rodríguez Vásquez et al. 2021]] ). However, the degree of incidence and regional trends are quite different and a study over 14 years indicated, on average, the largest fires in Australia, boreal North America and Northern Hemisphere Africa ( [[#Andela--2019|Andela et al. 2019]] ). More than half of the terrestrial surface of the Earth has fire regimes outside the range of natural variability, with changes in fire frequency and intensity posing major challenges for land restoration and recovery (Barger et al. 2018). In some ecosystems, fire prevention might lead to accumulation of large fuel loads that enable wildfires ( [[#Moreira--2020a|Moreira et al. 2020a]] ).

About 98 Mha of forest and savannahs are estimated to have been affected by fire in 2015 ( [[#FAO%20and%20UNEP--2020|FAO and]] [[#UNEP--2020|UNEP 2020]] ). Fire is a prevalent forest disturbance in the tropics where about 4% of the total forest and savannah area in that year was burned and more than two-thirds of the total area affected was in Africa and South America; mostly open savanna types ( [[#FAO%20and%20UNEP--2020|FAO and]] [[#UNEP--2020|UNEP 2020]] ). Fires have many different causes, with land clearing for agriculture the primary driver in tropical regions, for example, clearance for industrial oil-palm and paper-pulp plantations in Indonesia ( [[#Chisholm--2016|Chisholm et al. 2016]] ), or for pastures in the Amazon ( [[#Barlow--2020|Barlow et al. 2020]] ). Other socio-economic factors are also associated with wildfire regimes such as land-use conflict and socio-demographic aspects ( [[#Nunes--2016|Nunes et al. 2016]] ; [[#Mancini--2018|Mancini et al. 2018]] ). Wildfire regimes are also changing by the influence of climate change, with wildfire seasons becoming longer, wildfire average size increases in many areas and wildfires occurring in areas where they did not occur before ( [[#Jolly--2015|Jolly et al. 2015]] ; [[#Artés--2019|Artés et al. 2019]] ). Human influence has likely increased fire weather in some regions of all inhabited continents (IPCC AR6 WGI Technical Summary) and, in the last years, fire seasons of unprecedented magnitude occurred in diverse regions as California ( [[#Goss--2020|Goss et al. 2020]] ), the Mediterranean basin ( [[#Ruffault--2020|Ruffault et al. 2020]] ), Canada ( [[#Kirchmeier‐Young--2019|Kirchmeier‐Young et al. 2019]] ) with unprecedented fires in British Columbia in 2021, the Arctic and Siberia ( [[#McCarty--2020|McCarty et al. 2020]] ), Brazilian Amazon ( [[#Silva--2021|Silva et al. 2021]] ) and Pantanal ( [[#Leal%20Filho--2021|Leal Filho et al. 2021]] ), Chile ( [[#Bowman--2019|Bowman et al. 2019]] ) and Australia ( [[#Ward--2020|Ward et al. 2020]] ; [[#Gallagher--2021|Gallagher et al. 2021]] ). Lightning plays an important role in the ignition of wildfires, with the incidence of lightning igniting wildfires predicted to increase with rises in global average air temperature ( [[#Worden--2017|Worden et al. 2017]] ).

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