Assessing the Impacts of Fire on Forests (FS-22-01)
Fire can have positive or negative effects on forest ecosystems, depending on the characteristics of the forest and of the fire. The results of the interaction between fire, weather, and forests are often described using the terms fire severity and fire intensity. These terms are often used together, but have different meanings.
Fire severity–the impact of fire on forest ecosystems–is most often quantified as tree mortality, decrease in above-ground biomass, compositional changes to vegetation, or changes to soil properties. Fire intensity quantifies energy release from fire.
Information about past or predicted future wildfire intensity and wildfire severity can be used to model fire risk or fire hazard. For instance, variability in the distribution of different types of fuel across a landscape can be used to predict fire intensity, while predictions about fire behavior (i.e., crown fire potential) can be used to estimate severity.
This fact sheet presents the common measures of fire severity and fire intensity, and the importance of understanding these measures.