Under a high-emissions pathway Alaska's burned area more than doubles, and reaches up to eightfold in the Arctic
Jeremy Littell and colleagues drove the ALFRESCO landscape model with temperature and precipitation from five CMIP5 climate models to project this century's fire in boreal Alaska. In the study published in Earth's Future the median annual burned area rises under both emissions pathways, and more than doubles under high emissions. In the Arctic and western Alaska, where fire has historically been sparse, the increase reaches up to eightfold, and deciduous trees gain ground as repeated fire pushes spruce out.
Science··Morning
The median burned area rises under both emissions pathways
Jeremy Littell and colleagues fed temperature and precipitation from five climate models of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) into the Alaska Frame-Based Ecosystem Code (ALFRESCO) landscape model, and worked out the states that fire and vegetation composition in boreal Alaska could take this century. The projections cover both moderate and high levels of greenhouse-gas emissions. Individual models differ markedly in how they calculate the increase in burned area; even so, regardless of the emissions pathway the more likely outcome is a rise in the median annual area burned. Under the high-emissions scenario that rise more than doubles it. The study appeared in Earth's Future.[1], [2]
In the Arctic and western Alaska the increase reaches up to eightfold
The largest relative increases fall in the Arctic and western Alaska, where fire has historically been rarer, and there the projections reach up to eightfold. Tundra and permafrost carbon sit in the same geography. The model shifts the vegetation too: repeated fire pushes spruce species back while deciduous trees become steadily more dominant. Deciduous trees are less flammable than spruce, and that balance shapes later fire activity in turn. Where warming stays lower and summer precipitation increases, fire activity could stay within historical bounds.[1], [2]
What the authors leave fire managers: variety in the vegetation
What the authors leave for fire managers is that variety in the age, species makeup and spatial coverage of vegetation could reduce the likelihood of larger fires. Keeping and widening that variety through suppression, controlled burns and fuel treatments could be a useful management path. The study's own limit is that the fire-vegetation relationships in ALFRESCO were built on the historical record; under climates with no historical analogue the flammability of vegetation could behave differently, and the course of fire activity could change. Precipitation variability stands as the second loose term.[1], [2]
