Projections of Climate‐Driven Changes in Fire Regimes and Implications for Boreal Landscapes in Alaska and Northwest Canada

Abstract

Boreal fire regimes in Alaska are expected to change with climate. Recent fire activity increased regional deciduous boreal forest fraction and decreased spruce, potentially foreshadowing landscape transformations that would affect habitat, ecohydrologic function, ecosystem services, and contribute to global climate feedbacks. Future boreal trajectories are contingent on climatic drivers of and ecological responses to fire and thus defy forecasting, but plausible climate‐fire scenarios could allow land management entities to conduct more specific future assessments and develop adaptation strategies. Using downscaled monthly temperature and precipitation from five climate models from the fifth Coupled Model Intercomparison Project (CMIP5) for two representative concentration pathways (RCPs 4.5 and 8.5), we simulated historical and future fire activity with the landscape model ALFRESCO. We present projections of area burned, fire size, relative flammability, and vegetation responses for boreal Alaska. Regional area burned increases significantly under moderate (RCP4.5) and high (RCP8.5) scenarios. Model ensemble median annual area burned more than doubles by the end of the 21st century relative to the mid 20th century in interior Alaska under high emissions, but increases proportionally more (up to 8‐fold) in Arctic and western Alaska, assuming negative fire‐fuel feedbacks. Under fire season warming greater than 3°C, fire regimes change rapidly and black and white spruce forests are largely replaced by deciduous forest. These changes vary at finer scales, but regional increases in area burned are eventually limited by fuel feedbacks. We summarize these futures for different regions (Arctic, interior, and western Alaska) and for 25 land‐management units.