Fire, Fuel, and Climate Interactions in Temperate Climates

• Published in: AGU advances Vol. 6; no. 2
• Main Authors: Kampf, Stephanie K., Stevens‐Rumann, Camille S., Nunes, Leónia, Sequeira, Ana Catarina, Rego, Francisco Castro, Fernández, Cristina, Hernández‐Duarte, Ana, Mosso, Clara E., Francois, Jean Pierre, Miranda, Alejandro
• Format: Journal Article
• Language: English
• Published: Wiley 01.04.2025
• Subjects: aridity; climate change; fuel; temperate regions; wildfire
• ISSN: 2576-604X; 2576-604X
• DOI: 10.1029/2024AV001628

Temperate regions around the world are experiencing longer fire weather seasons, yet trends in burned area have been inconsistent between regions. Reasons for differences in fire patterns can be difficult to determine due to variable vegetation types, land use patterns, fuel conditions, and human influences on fire ignition and suppression. This study compares burned areas to climate and fuel conditions in three temperate regions: the desert, shrub, and forest ecoregions of western North America, west‐central Europe, and southwestern South America. In each region the mean annual aridity index (AI, precipitation over potential evapotranspiration) spans arid to humid climates. We examined how the fraction of area burned from 2001 to 2021 varied with mean annual AI, mean aboveground biomass, and land cover type distributions. All three regions had low fractions of area burned for the driest climate zones (AI < 0.5), a sign of fuel limitation to burned area. Fraction of area burned increased with mean aboveground biomass for these dry zones. Fraction of area burned peaked at intermediate AI (0.7–1.5) for all regions and declined again in the wettest climate zones (AI > 1.5), a sign of climate limitation to burned area. Of the three regions, western North America had the highest burned area, fraction of area burned, and fire sizes. Fragmentation of vegetation patches by the high Andes Mountains in southwestern South America and by intensive land use changes in west‐central Europe likely limited fire sizes. All three regions are at risk for future wildfires, particularly in areas where fire is currently climate limited. Plain Language Summary Warmer temperatures around the world are lengthening fire seasons, leading to large wildfires. We compared the burned areas in three regions that have large variations in climate and vegetation: western North America, west‐central Europe, and southwestern South America. We found that in the driest parts of each region, very little area burned because the vegetation is sparse, limiting the spread of fire. The area burned was also low in the wettest parts of these regions because the weather conditions were often not conducive to fire. The percent of area burned was highest in the intermediate climates, which have both enough vegetation for fire to spread and dry enough weather for wildfire. Among the three regions, the burned areas have been largest in western North America, which has the largest continuous extents of vegetation to burn. In southwestern South America, the forests and shrublands are broken up by the high Andes Mountains, and in west‐central Europe, extensive land use has limited the size of burnable areas. All three regions are at risk for large wildfires in the future, especially in the wettest areas where climate warming will make fire weather more likely. Key Points Evaluated burned area, climate, and fuel relationships in temperate desert, shrub, and forest ecoregions in N. & S. America and Europe All regions have different patterns of burned areas between the dry fuel‐limited and wet climate‐limited conditions Sizes of individual fires, total burned area, and fraction of area burned have been highest in western N. America and smallest in Europe