Effects of fuel types and fire severity on atmospheric pollutant emissions in an extreme wind-driven wildfire

Abstract

In the Mediterranean region, wind-driven crown fires are becoming more frequent, leading to increased atmospheric pollutant emissions. This study explored how the distribution of pre-fire fuels across the crown, shrub and litter layers varies among different fuel types, and how these variations were linked with fuel consumption and fire severity for each layer to quantify and compare atmospheric pollutant emissions (CO₂, CO, CH₄ and PM_2.5) in pine (Pinus halepensis) and oak (Quercus suber) forests. Our analysis was carried out in the Jonquera wildfire in Northeast Spain, which burned 10,264 ha. Pre-fire fuel loading among fuel types in pine and oak forests showed different vertical distributions despite, having similar fire-type patterns. Pine forests had a higher percentage of crown and shrub fuel loading for all fuel. In contrast, oak forests had more litter than pine forest. Fuel types characterized by large trees and low densities had the lowest fire severity in both forest types. Pine forests were more resistant to the effects of surface fires than oak forests due to their taller trees, which allowed them to withstand high-intensity surface fires with less tree damage. However, these fires have resulted in higher surface fuel consumption in pine forests. Fuel types with more vertical and horizontal continuity experienced higher fire severity and fuel consumption (72–85% of high severity). Fire severity rather than species or fuel type was the primary factor influencing pollutant emissions. Emissions of CO₂ and CH₄ were higher in pine than in oak forests especially at lower severities, while at intermediate and higher severity oak forests emitted more CO and PM_2.5. Although remote sensing technologies are useful for fuel loading and wildfire severity assessments, field data are essential for accurately quantifying fuel consumption across fuel types and layers.

Keywords

Fuel loading / Fuel consumption / Forest structure / Pinus halepensis / Quercus suber / Pyrogenic emissions

References

[1] Abdollahi A, Yebra M. Forest fuel type classification: review of remote sensing techniques, constraints and future trends. J Environ Manage. 2023, 342. 118315

[2] Aghajani H, Fallah A, Fazlollah Emadian S. Modelling and analyzing the surface fire behaviour in Hyrcanian forest of Iran. J for Sci. 2014, 60(9): 353-362.

[3] Akin ID, Akinleye TO, Robichaud PR. Changes in soil properties over time after a wildfire and implications to slope stability. J Geotech Geoenviron Eng. 2023, 149(7. 04023045

[4] Alves CA, Vicente A, Monteiro C, Gonçalves C, Evtyugina M, Pio C. Emission of trace gases and organic components in smoke particles from a wildfire in a mixed-evergreen forest in Portugal. Sci Total Environ. 2011, 4098): 1466-1475.

[5] Alvarez A, Gracia M, Retana J. Fuel types and crown fire potential in Pinus halepensis forests. Eur J for Res. 2012, 131(2): 463-474.

[6] Alvarez A, Gracia M, Vayreda J, Retana J. Patterns of fuel types and crown fire potential in Pinus halepensis forests in the Western Mediterranean Basin. For Ecol Manag. 2012, 270: 282-290.

[7] Alvarez A, Gracia M, Castellnou M, Retana J. Variables that influence changes in fire severity and their relationship with changes between surface and crown fires in a wind-driven wildfire. For Sci. 2013, 59(2): 139-150.

[8] Bacciu V, Salis M, Spano D, Arca B, Pellizzaro G, Duce P (2009) Assessment of smoke emission and carbon estimates from Mediterranean Maquis fire events. In: Eighth symposium on fire and forest meteorology. American Meteorological Society, Kalispell. https://ams.confex.com/ams/8Fire/techprogram/paper_156372.htm

[9] Bacciu V, Spano D, Salis M. Valentini R, Miglietta F. Emissions from forest fires: methods of estimation and national results. The greenhouse gas balance of italy: an insight on managed and natural terrestrial ecosystems. 2015, Berlin, Heidelberg, Springer87102.

[10] Badia A, Pallares-Barbera M, Valldeperas N, Gisbert M. Wildfires in the wildland-urban interface in Catalonia: vulnerability analysis based on land use and land cover change. Sci Total Environ. 2019, 673: 184-196.

[11] Balde B, Vega-Garcia C, Gelabert PJ, Ameztegui A, Rodrigues M. The relationship between fire severity and burning efficiency for estimating wildfire emissions in Mediterranean forests. J for Res. 2023, 34(5): 1195-1206.

[12] Beltrán-Marcos D, Suárez-Seoane S, Fernández-Guisuraga JM, Azevedo JC, Calvo L. Fire regime attributes shape pre-fire vegetation characteristics controlling extreme fire behavior under different bioregions in Spain. Fire Ecol. 2024, 20(1. 47

[13] Bowman DMJS, Balch JK, Artaxo P, Bond WJ, Carlson JM, Cochrane MA, D’Antonio CM, DeFries RS, Doyle JC, Harrison SP, Johnston FH, Keeley JE, Krawchuk MA, Kull CA, Marston JB, Moritz MA, Prentice IC, Roos CI, Scott AC, Swetnam TW, van der Werf GR, Pyne SJ. Fire in the Earth system. Science. 2009, 3245926): 481-484.

[14] Busby SU, Klock AM, Fried JS. Inventory analysis of fire effects wrought by wind-driven megafires in relation to weather and pre-fire forest structure in the western Cascades. Fire Ecol. 2023, 19(1. 58

[15] Call PT, Albini FA. Aerial and surface fuel consumption in crown fires. Int J Wildland Fire. 1997, 73): 259-264.

[16] Campbell J, Donato D, Azuma D, Law B. Pyrogenic carbon emission from a large wildfire in Oregon, United States. J Geophys Res Biogeosciences. 2007, 112(G4. 2007JG000451

[17] Carvalho A, Monteiro A, Flannigan M et al (2007) Forest fire emissions under climate change: impacts on air quality. In: Seventh symposium on fire and forest meteorology. American Meteorological Society, The Turrets. https://ams.confex.com/ams/7firenortheast/techprogram/paper_126854.htm

[18] Casals P, Valor T, Besalú A, Molina-Terrén D. Understory fuel load and structure eight to nine years after prescribed burning in Mediterranean pine forests. For Ecol Manag. 2016, 362: 156-168.

[19] Casals P, Gabriel E, De Cáceres M, Ríos AI, Castro X. Composition and structure of Mediterranean shrublands for fuel characterization. Ann for Sci. 2023, 801. 23

[20] Chaves Naharro J (2015) Forest fires and climate change. Estimation of emissions from the fires in Andilla and Cortes de Pallás. Master’s Thesis. Universitat Politècnica de València. https://riunet.upv.es/handle/10251/51839

[21] Chiriacò MV, Perugini L, Cimini D, D’Amato E, Valentini R, Bovio G, Corona P, Barbati A. Comparison of approaches for reporting forest fire-related biomass loss and greenhouse gas emissions in southern Europe. Int J Wildland Fire. 2013, 226): 730-738.

[22] Chowdhury S, Hänninen R, Sofiev M, Aunan K. Fires as a source of annual ambient PM_2.5 exposure and chronic health impacts in Europe. Sci Total Environ. 2024, 922. 171314

[23] CIFFC (2023) Canadian Wildland Fire Management Glossary. Can Interag For Fire Cent Winnipeg, MB, Canada. https://www.ciffc.ca/sites/default/files/2023-04/CWFM_glossary_v2023-04-24-EN.pdf

[24] Conedera M, Feusi J, Pezzatti GB, Krebs P. Linking the future likelihood of large fires to occur on mountain slopes with fuel connectivity and topography. Nat Hazards. 2024, 120(5): 4657-4673.

[25] Conrad ET, Jolly WM, Brown TP, Hillman SC. Branching out: species-specific canopy architecture limits live crown fuel consumption in Intermountain West USA conifers. Fire Ecol. 2024, 20(1. 28

[26] Costa P, Castellnou M, Larrañaga A, Miralles M, Kraus D (2011) Prevention of Large Wildfires using the Fire Types Concept. Departament de Interior. Generalitat de Catalunya., Cerdanyola del Vallès, Barcelona, Spain. https://interior.gencat.cat/ca/el_departament/publicacions/proteccio_civil/la_prevencio_dels_grans_incendis_forestals_adaptada_a_l_incendi_tipus/index.html

[27] CREAF (2009) Land Cover Map of Catalonia (MCSC). http://www.creaf.uab.es/mcsc/descriptiu.htm

[28] Curt T, Schaffhauser A, Borgniet L, Dumas C, Estève R, Ganteaume A, Jappiot M, Martin W, N’Diaye A, Poilvet B. Litter flammability in oak woodlands and shrublands of southeastern France. For Ecol Manag. 2011, 26112): 2214-2222.

[29] Cruz MG, Hoffman CM, Fernandes PM. Global synthesis of quantification of fire behaviour characteristics in forests and shrublands: recent progress. Curr for Rep. 2025, 11(1. 8

[30] Çinar T, Taşpinar F, Aydin A. Analysis and estimation of gaseous air pollutant emissions emitted into the atmosphere during Manavgat and Milas wildfire episodes using remote sensing data and ground measurements. Air Qual Atmos Health. 2024, 173): 559-579.

[31] DARP (2012) Report on the forest fire of July 22, 2012 in La Jonquera (Alt Empordà), Generalitat de Catalunya, Departament d'Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural, Girona, Spain. https://agricultura.gencat.cat/web/.content/06-medi-natural/boscos/gestio-forestal/obres/restauracio-forestal/restauracio-hidrologica/fitxers-binaris/jonquera_informe_incendi.pdf

[32] De Cáceres M, Martínez-Vilalta J, Coll L, Llorens P, Casals P, Poyatos R, Pausas JG, Brotons L. Coupling a water balance model with forest inventory data to predict drought stress: the role of forest structural changes vs. climate changes. Agric for Meteorol. 2015, 213: 77-90.

[33] de Rigo D, Libertà G, Houston Durrant T, Artés T, San Miguel Ayanz J (2017) Forest fire danger extremes in Europe under climate change: variability and uncertainty. Publ Off Eur Union. JRC108974. https://doi.org/10.2760/13180

[34] De Santis A, Asner GP, Vaughan PJ, Knapp DE. Mapping burn severity and burning efficiency in California using simulation models and Landsat imagery. Remote Sens Environ. 2010, 114(7): 1535-1545.

[35] Dimitrakopoulos AP. Mediterranean fuel models and potential fire behaviour in Greece. Int J Wildland Fire. 2002, 11(2): 127-130.

[36] Dimitrakopoulos AP, Mitsopoulos ID, Raptis DI. Nomographs for predicting crown fire initiation in Aleppo pine (Pinus halepensis Mill.) forests. Eur J Forest Res. 2007, 126(4): 555-561.

[37] Domingo D, Lamelas-Gracia MT, Montealegre-Gracia AL, de la Riva-Fernández J. Comparison of regression models to estimate biomass losses and CO₂ emissions using low-density airborne laser scanning data in a burnt Aleppo pine forest. Eur J Remote Sens. 2017, 50(1): 384-396.

[38] Duane A, Brotons L. Synoptic weather conditions and changing fire regimes in a Mediterranean environment. Agric for Meteorol. 2018, 253: 190-202.

[39] Fernandes PM. Combining forest structure data and fuel modelling to classify fire hazard in Portugal. Ann for Sci. 2009, 66. 415

[40] Fernandes PM, Fernandes MM, Loureiro C. Post-fire live residuals of maritime pine plantations in Portugal: structure, burn severity, and fire recurrence. For Ecol Manag. 2015, 347: 170-179.

[41] Fernandes AP, Lopes D, Sorte S, Monteiro A, Gama C, Reis J, Menezes I, Osswald T, Borrego C, Almeida M, Ribeiro LM, Viegas DX, Miranda AI. Smoke emissions from the extreme wildfire events in central Portugal in October 2017. Int J Wildland Fire. 2022, 31(11): 989-1001.

[42] Fernandes PM, Loureiro C. Fine fuels consumption and CO₂ emissions from surface fire experiments in maritime pine stands in northern Portugal. For Ecol Manag. 2013, 291: 344-356.

[43] Fernández-García V, Beltrán-Marcos D, Fernández-Guisuraga JM, Marcos E, Calvo L. Predicting potential wildfire severity across Southern Europe with global data sources. Sci Total Environ. 2022, 829. 154729

[44] Fernández-Guisuraga JM, Fernandes PM, Fernández-Guisuraga JM, Fernandes PM. Using pre-fire high point cloud density LiDAR data to predict fire severity in central Portugal. Remote Sens. 2023, 15(3. 768

[45] Ficken CD, Wright JP. Effects of fire frequency on litter decomposition as mediated by changes to litter chemistry and soil environmental conditions. PLoS ONE. 2017, 1210. e0186292

[46] Filonchyk M, Peterson MP, Zhang LM, Zhang LF, He Y. Estimating air pollutant emissions from the 2024 wildfires in Canada and the impact on air quality. Gondwana Res. 2025, 140: 194-204.

[47] Fortems-Cheiney A, Broquet G, Potier E, Plauchu R, Berchet A, Pison I, van der Denier Gon H, Dellaert S. CO anthropogenic emissions in Europe from 2011 to 2021: insights from Measurement of Pollution in the Troposphere (MOPITT) satellite data. Atmos Chem Phys. 2024, 248): 4635-4649.

[48] French NHF, de Groot WJ, Jenkins LK, Rogers BM, Alvarado E, Amiro B, de Jong B, Goetz S, Hoy E, Hyer E, Keane R, Law BE, McKenzie D, McNulty SG, Ottmar R, Pérez-Salicrup DR, Randerson J, Robertson KM, Turetsky M. Model comparisons for estimating carbon emissions from North American wildland fire. J Geophys Res. 2011, 116. G00K05

[49] Fulé PZ, Ribas M, Gutiérrez E, Vallejo R, Kaye MW. Forest structure and fire history in an old Pinus nigra forest, eastern Spain. For Ecol Manag. 2008, 255(3–4): 1234-1242.

[50] Gabriel E, Delgado-Dávila R, De Cáceres M, Casals P, Tudela A, Castro X. Live fuel moisture content time series in Catalonia since 1998. Ann for Sci. 2021, 78(2. 44

[51] Ganteaume A, Jappiot M, Curt T, Lampin C, Borgniet L. Flammability of litter sampled according to two different methods: comparison of results in laboratory experiments. Int J Wildland Fire. 2014, 238): 1061-1075.

[52] Ganteaume A, Lampin-Maillet C, Guijarro M, Hernando C, Jappiot M, Fonturbel T, Pérez-Gorostiaga P, Vega JA. Spot fires: fuel bed flammability and capability of firebrands to ignite fuel beds. Int J Wildland Fire. 2009, 18(8): 951-969.

[53] Garcia-Hurtado E, Pey J, Baeza MJ, Carrara A, Llovet J, Querol X, Alastuey A, Vallejo VR. Carbon emissions in Mediterranean shrubland wildfires: an experimental approach. Atmos Environ. 2013, 69: 86-93.

[54] González JR, Trasobares A, Palahí M, Pukkala T. Predicting stand damage and tree survival in burned forests in Catalonia (North-East Spain). Ann for Sci. 2007, 64(7): 733-742.

[55] Gracia C (2001) (Ed) Inventari Ecològic i Forestal de Catalunya, Regio forestal III, CREAF, Bellaterra, Spain

[56] Griffin D, Chen J, Anderson K, Makar P, McLinden CA, Dammers E, Fogal A. Towards an improved understanding of wildfire CO emissions: a satellite remote-sensing perspective. Egusphere. 2023, 2023: 1-37.

[57] Hessburg PF, Spies TA, Perry DA, Skinner CN, Taylor AH, Brown PM, Stephens SL, Larson AJ, Churchill DJ, Povak NA, Singleton PH, McComb B, Zielinski WJ, Collins BM, Salter RB, Keane JJ, Franklin JF, Riegel G. Tamm review: management of mixed-severity fire regime forests in Oregon, Washington, and Northern California. For Ecol Manag. 2016, 366: 221-250.

[58] Hoff V, Rowell E, Teske C, Queen L, Wallace T, Hoff V, Rowell E, Teske C, Queen L, Wallace T. Assessing the relationship between forest structure and fire severity on the north rim of the Grand Canyon. Fire. 2019, 2(1. 10

[59] Jain TB, Graham RT (2007) The relation between tree burn severity and forest structure in the rocky mountains. Gen Tech Rep PSW-GTR-203USDA For Serv Rocky Mt Res Stn. https://www.fs.usda.gov/psw/publications/documents/psw_gtr203/psw_gtr203_017jain.pdf

[60] Jiménez E, Vega JA, Ruiz-González AD, Guijarro M, Alvarez-González JG, Madrigal J, Cuiñas P, Hernando C, Fernández-Alonso JM. Carbon emissions and vertical pattern of canopy fuel consumption in three Pinus pinaster Ait. active crown fires in Galicia (NW Spain). Ecol Eng. 2013, 54: 202-209.

[61] Kane VR, McGaughey RJ, Bakker JD, Gersonde RF, Lutz JA, Franklin JF. Comparisons between field- and LiDAR-based measures of stand structural complexity. Can J for Res. 2010, 404): 761-773.

[62] Keeley JE. Fire intensity, fire severity and burn severity: a brief review and suggested usage. Int J Wildland Fire. 2009, 18(1): 116-126.

[63] Keeley JE, Syphard AD. Twenty-first century California, USA, wildfires: fuel-dominated vs. wind-dominated fires. Fire Ecol. 2019, 15(1. 24

[64] Kennedy MC, Prichard SJ, McKenzie D, French NHF. Quantifying how sources of uncertainty in combustible biomass propagate to prediction of wildland fire emissions. Int J Wildland Fire. 2020, 299): 793-806.

[65] Keywood M, Kanakidou M, Stohl A, Dentener F, Grassi G, Meyer CP, Torseth K, Edwards D, Thompson AM, Lohmann U, Burrows J. Fire in the air: biomass burning impacts in a changing climate. Crit Rev Environ Sci Technol. 2013, 43(1): 40-83.

[66] Knorr W, Jiang L, Arneth A. Climate, CO₂ and human population impacts on global wildfire emissions. Biogeosciences. 2016, 13(1): 267-282.

[67] Kocbach Bølling A, Pagels J, Yttri KE, Barregard L, Sallsten G, Schwarze PE, Boman C. Health effects of residential wood smoke particles: the importance of combustion conditions and physicochemical particle properties. Part Fibre Toxicol. 2009, 6. 29

[68] Labenski P, Ewald M, Schmidtlein S, Heinsch FA, Fassnacht FE. Quantifying surface fuels for fire modelling in temperate forests using airborne lidar and Sentinel-2: potential and limitations. Remote Sens Environ. 2023, 295. 113711

[69] Lahaye S, Curt T, Fréjaville T, Sharples J, Paradis L, Hély C. What are the drivers of dangerous fires in Mediterranean France. Int J Wildland Fire. 2018, 27(3): 155-163.

[70] Larkin NK, Raffuse SM, Strand TM. Wildland fire emissions, carbon, and climate: U.S. emissions inventories. For Ecol Manage. 2014, 317: 61-69.

[71] Lasslop G, Kloster S. Impact of fuel variability on wildfire emission estimates. Atmos Environ. 2015, 121: 93-102.

[72] Lazaridis M, Latos M, Aleksandropoulou V, Hov Ø, Papayannis A, Tørseth K. Contribution of forest fire emissions to atmospheric pollution in Greece. Air Qual Atmos Health. 2008, 1(3): 143-158.

[73] Lecina-Diaz J, Alvarez A, Retana J. Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests. PLoS ONE. 2014, 9(1. e85127

[74] Lecina-Diaz J, Martínez-Vilalta J, Alvarez A, Vayreda J, Retana J. Assessing the risk of losing forest ecosystem services due to wildfires. Ecosystems. 2021, 247): 1687-1701.

[75] Lecina-Diaz J, Senf C, Grünig M, Seidl R. Ecosystem services at risk from disturbance in Europe’s forests. Glob Change Biol. 2024, 30(3. e17242

[76] Liang YT, Stamatis C, Fortner EC, Wernis RA, Van Rooy P, Majluf F, Yacovitch TI, Daube C, Herndon SC, Kreisberg NM, Barsanti KC, Goldstein AH. Emissions of organic compounds from western US wildfires and their near-fire transformations. Atmos Chem Phys. 2022, 2215): 9877-9893.

[77] Lydersen JM, Collins BM, Ewell CM, Reiner AL, Fites JA, Dow CB, Gonzalez P, Saah DS, Battles JJ. Using field data to assess model predictions of surface and ground fuel consumption by wildfire in coniferous forests of California. J Geophys Res Biogeosci. 2014, 119(3): 223-235.

[78] Ma YF, Yang S, Zhu ZP, Wang GY, Tigabu M, Guo YX, Zheng WX, Guo FT. Emissions of gaseous pollutants released by forest fire in relation to litter fuel moisture content. Atmos Environ. 2022, 284. 119215

[79] MCSC (2010) https://www.mcsc.creaf.cat/

[80] Merrill DF, Alexander ME (1987) Glossary of forest fire management terms. Can Comm For Fire Manag Natl Res Counc Canada Ottawa

[81] Miranda AI. An integrated numerical system to estimate air quality effects of forest fires. Int J Wildl Fire. 2004, 13(2): 217-226.

[82] Miranda AI, Ferreira J, Valente J, Santos P, Amorim JH, Borrego C. Smoke measurements during Gestosa-2002 experimental field fires. Int J Wildland Fire. 2005, 14(1): 107-116.

[83] Miranda AI, Borrego C, Martins H, Martins V, Amorim JH, Valente J, Carvalho A (2009) Forest fire emissions and air pollution in southern Europe. In: Earth observation of wildland fires in Mediterranean ecosystems. Springer, pp 171–187. https://doi.org/10.1007/978-3-642-01754-4_12

[84] Mitsopoulos ID, Dimitrakopoulos AP. Canopy fuel characteristics and potential crown fire behavior in Aleppo pine (Pinus halepensis Mill.) forests. Ann for Sci. 2007, 64(3): 287-299.

[85] Mitsopoulos ID, Dimitrakopoulos AP. Estimation of canopy fuel characteristics of Aleppo pine (Pinus halepensis Mill.) forests in Greece based on common stand parameters. Eur J Forest Res. 2014, 133(1): 73-79.

[86] Molina JR, Herrera MA, Rodríguez y Silva F. Wildfire-induced reduction in the carbon storage of Mediterranean ecosystems: an application to brush and forest fires impacts assessment. Environ Impact Assess Rev. 2019, 76: 88-97.

[87] Naeher LP, Brauer M, Lipsett M, Zelikoff JT, Simpson CD, Koenig JQ, Smith KR. Woodsmoke health effects: a review. Inhal Toxicol. 2007, 19(1): 67-106.

[88] Nunes L, Álvarez-González J, Alberdi I, Silva V, Rocha M, Rego FC. Analysis of the occurrence of wildfires in the Iberian Peninsula based on harmonised data from national forest inventories. Ann for Sci. 2019, 76(1. 27

[89] Oliveras I, Gracia M, Moré G, Retana J. Factors influencing the pattern of fire severities in a large wildfire under extreme meteorological conditions in the Mediterranean basin. Int J Wildland Fire. 2009, 187): 755-764.

[90] Ottmar RD, Miranda AI, Sandberg DV (2008) Chapter 3 characterizing sources of emissions from wildland fires. In: Wildland fires and air pollution. Elsevier, pp 61–78. https://doi.org/10.1016/s1474-8177(08)00003-x

[91] Pallozzi E, Lusini I, Cherubini L, Hajiaghayeva RA, Ciccioli P, Calfapietra C. Differences between a deciduous and a conifer tree species in gaseous and particulate emissions from biomass burning. Environ Pollut. 2018, 234: 457-467.

[92] Pasalodos-Tato M, Ruiz-Peinado R, del Río M, Montero G. Shrub biomass accumulation and growth rate models to quantify carbon stocks and fluxes for the Mediterranean region. Eur J Forest Res. 2015, 134(3): 537-553.

[93] Poupkou A, Markakis K, Liora N, Giannaros TM, Zanis P, Im U, Daskalakis N, Myriokefalitakis S, Kaiser JW, Melas D, Kanakidou M, Karacostas T, Zerefos C. A modeling study of the impact of the 2007 Greek forest fires on the gaseous pollutant levels in the Eastern Mediterranean. Atmos Res. 2014, 149: 1-17.

[94] Price OH, Nolan RH, Samson SA. Fuel consumption rates in resprouting eucalypt forest during hazard reduction burns, cultural burns and wildfires. For Ecol Manag. 2022, 505. 119894

[95] Prichard SJ, O’Neill SM, Eagle P, Andreu AG, Drye B, Dubowy J, Urbanski S, Strand TM. Wildland fire emission factors in North America: synthesis of existing data, measurement needs and management applications. Int J Wildland Fire. 2020, 29(2): 132-147.

[96] Prichard SJ, Povak NA, Kennedy MC, Peterson DW. Fuel treatment effectiveness in the context of landform, vegetation, and large, wind-driven wildfires. Ecol Appl. 2020, 30(5. e02104

[97] Prichard SJ, Rowell EM, Hudak AT, Keane RE, Loudermilk EL, Lutes DC, Ottmar RD, Chappell LM, Hall JA, Hornsby BS (2022) Fuels and consumption. In: Wildland fire smoke in the United States. Springer, pp 11–49. https://doi.org/10.1007/978-3-030-87045-4_2

[98] Ritter SM, Hoffman CM, Battaglia MA, Linn R, Mell WE. Vertical and horizontal crown fuel continuity influences group-scale ignition and fuel consumption. Fire. 2023, 68): 321.

[99] Rodrigues M, Cunill Camprubí À, Balaguer-Romano R, Coco Megía CJ, Castañares F, Ruffault J, Fernandes PM, de Resco Dios V. Drivers and implications of the extreme 2022 wildfire season in Southwest Europe. Sci Total Environ. 2023, 859. 160320

[100] Rosa IMD, Pereira JMC, Tarantola S. Atmospheric emissions from vegetation fires in Portugal (1990–2008): estimates, uncertainty analysis, and sensitivity analysis. Atmos Chem Phys. 2011, 1162625-2640.

[101] Ruffault J, Moron V, Trigo RM, Curt T. Daily synoptic conditions associated with large fire occurrence in Mediterranean France: evidence for a wind-driven fire regime. Int J Climatol. 2017, 37(1): 524-533.

[102] Ruffault J, Curt T, Martin-StPaul NK, Moron V, Trigo RM. Extreme wildfire events are linked to global-change-type droughts in the northern Mediterranean. Nat Hazards Earth Syst Sci. 2018, 18(3): 847-856.

[103] Salana S, Yu HR, Dai ZY, Ganesh Subramanian PS, Puthussery JV, Wang YX, Singh A, Pope FD, Leiva GMA, Rastogi N, Tripathi SN, Weber RJ, Verma V. Inter-continental variability in the relationship of oxidative potential and cytotoxicity with PM_2.5 mass. Nat Commun. 2024, 15(1. 5263

[104] Salis M, Arca B, Alcasena-Urdiroz F, Massaiu A, Bacciu V, Bosseur F, Caramelle P, Dettori S, de Fernans Oliveira AS, Molina-Terren D, Pellizzaro G, Santoni PA, Spano D, Vega-Garcia C, Duce P. Analyzing the recent dynamics of wildland fires in Quercus suber L. woodlands in Sardinia (Italy), Corsica (France) and Catalonia (Spain). Eur J Forest Res. 2019, 1383): 415-431.

[105] San-Miguel-Ayanz J, Steinbrecher R (2019) EMEP/EEA air pollutant emission inventory guidebook 2019: Forest and other vegetation fires, European Environment Agency, Tech. https://www.eea.europa.eu/publications/emep-eea-guidebook-2019/part-b-sectoral-guidance-chapters/11-natural-sources/11-b-forest-fires/view

[106] San-Miguel-Ayanz J, Durrant T, Boca R, Maianti P, Liberta G, Jacome Felix Oom D, Branco A, De Rigo D, Suarez-Moreno M, Ferrari D, Roglia E, Scionti N, Broglia M, Onida M, Tistan A, Loffler P (2022) Forest Fires in Europe, Middle East and North Africa 2022

[107] Sánchez-Pinillos M, De Cáceres M, Casals P, Alvarez A, Beltrán M, Pausas JG, Vayreda J, Coll L. Spatial and temporal variations of overstory and understory fuels in Mediterranean landscapes. For Ecol Manage. 2021, 490. 119094

[108] Schaffhauser A, Curt T, Tatoni T. Fire-vegetation interplay in a mosaic structure of Quercus suber woodlands and Mediterranean maquis under recurrent fires. For Ecol Manage. 2011, 262(5): 730-738.

[109] Schaffhauser A, Pimont F, Curt T, Cassagne N, Dupuy JL, Tatoni T. Effects of fire recurrence on fire behaviour in cork oak woodlands (Quercus suber L.) and Mediterranean shrublands over the last fifty years. CR Biol. 2015, 338(12): 812-824.

[110] Seiler W, Crutzen PJ. Estimates of gross and net fluxes of carbon between the biosphere and the atmosphere from biomass burning. Clim Change. 1980, 2(3): 207-247.

[111] Shakoor A, Farooq TH, Arif MS, Shahzad SM. Unprecedented wildfires in Canada and transboundary effects of carbon monoxide pollution. Nat Hazards J Int Soc Prev Mitig Nat Hazards. 2023, 118(3): 2711-2713

[112] Silva TP, Pereira JMC, Paúl JCP, Santos MTN, Vasconcelo MJP. Estimated atmospheric emissions originated from rural fires in Portugal. Silva Lusit. 2006, 14(2): 239-263

[113] Sommers WT, Loehman RA, Hardy CC. Wildland fire emissions, carbon, and climate: science overview and knowledge needs. For Ecol Manage. 2014, 317: 1-8.

[114] Stocks BJ. Fire potential in the spruce budworm-damaged forests of Ontario. For Chron. 1987, 63(1): 8-14.

[115] Stocks BJ. Fire behavior in immature jack pine. Can J for Res. 1987, 17(1): 80-86.

[116] Stocks BJ. Fire behavior in mature jack pine. Can J for Res. 1989, 19(6): 783-790.

[117] Surawski NC, Sullivan AL, Roxburgh SH, Polglase PJ. Estimates of greenhouse gas and black carbon emissions from a major Australian wildfire with high spatiotemporal resolution. J Geophys Res Atmos. 2016, 121(16): 9892-9907.

[118] Tedim F, Leone V, Amraoui M, Bouillon C, Coughlan M, Delogu G, Fernandes P, Ferreira C, McCaffrey S, McGee T, Parente J, Paton D, Pereira M, Ribeiro L, Viegas D, Xanthopoulos G. Defining extreme wildfire events: difficulties, challenges, and impacts. Fire. 2018, 1(1. 9

[119] Urbanski SP. Combustion efficiency and emission factors for wildfire-season fires in mixed conifer forests of the northern Rocky Mountains, US. Atmos Chem Phys. 2013, 1314): 7241-7262.

[120] Urbanski S. Wildland fire emissions, carbon, and climate: emission factors. For Ecol Manage. 2014, 317: 51-60.

[121] Urbanski SP, Long RW, Halliday H, Lincoln EN, Habel A, Landis MS. Fuel layer specific pollutant emission factors for fire prone forest ecosystems of the western U.S. and Canada. Atmos Environ X. 2022, 16: 1-17.

[122] Varner JM, Kane JM, Kreye JK, Engber E. The flammability of forest and woodland litter: a synthesis. Curr for Rep. 2015, 1(2): 91-99.

[123] van der Werf GR, Randerson JT, Giglio L, van Leeuwen TT, Chen Y, Rogers BM, Mu MQ, van Marle MJE, Morton DC, Collatz GJ, Yokelson RJ, Kasibhatla PS. Global fire emissions estimates during 1997–2016. Earth Syst Sci Data. 2017, 9(2): 697-720.

[124] van Wees D, van der Werf GR, Randerson JT, Rogers BM, Chen Y, Veraverbeke S, Giglio L, Morton DC. Global biomass burning fuel consumption and emissions at 500 m spatial resolution based on the Global Fire Emissions Database (GFED). Geosci Model Dev. 2022, 15(22): 8411-8437.

[125] Vayreda J, Martínez-Vilalta J, Vilà-Cabrera A. The ecological forest inventory of Catalonia: a tool for functional ecology. Ecosistemas. 2016, 25(3): 70-79.

[126] Vicente-Serrano SM, Beguería S, López-Moreno JI. A multiscalar drought index sensitive to global warming: the standardized precipitation evapotranspiration index. J Clim. 2010, 23(7): 1696-1718.

[127] Viedma O, Chico F, Fernández JJ, Madrigal C, Safford HD, Moreno JM. Disentangling the role of prefire vegetation vs. burning conditions on fire severity in a large forest fire in SE Spain. Remote Sens Environ. 2020, 247. 111891

[128] Vilén T, Fernandes PM. Forest fires in Mediterranean countries: CO₂ emissions and mitigation possibilities through prescribed burning. Environ Manage. 2011, 48(3): 558-567.

[129] Wiedinmyer C, Quayle B, Geron C, Belote A, McKenzie D, Zhang XY, O’Neill S, Wynne KK. Estimating emissions from fires in North America for air quality modeling. Atmos Environ. 2006, 40(19): 3419-3432.

[130] Wiedinmyer C, Kimura Y, McDonald-Buller EC, Emmons LK, Buchholz RR, Tang WF, Seto K, Joseph MB, Barsanti KC, Carlton AG, Yokelson R. The fire inventory from NCAR version 2.5: an updated global fire emissions model for climate and chemistry applications. Geosci Model Dev. 2023, 16(13): 3873-3891.

[131] Xanthopoulos G, Calfapietra C, Fernandes P (2011) Fire hazard and flammability of European forest types. In: Post-fire management and restoration of southern European forests. Springer, pp 79–92. https://doi.org/10.1007/978-94-007-2208-8_4

[132] Yilmaz OS, Acar U, Sanli FB, Gulgen F, Ates AM. Mapping burn severity and monitoring CO content in Türkiye’s 2021 wildfires, using Sentinel-2 and Sentinel-5P satellite data on the GEE platform. Earth Sci Inform. 2023, 16(1): 221-240.

[133] Zheng B, Ciais P, Chevallier F, Chuvieco E, Chen Y, Yang H. Increasing forest fire emissions despite the decline in global burned area. Sci Adv. 2021, 739. eabh2646

Funding

Universitat Autònoma de Barcelona

RIGHTS & PERMISSIONS

The Author(s)