Fire severity relates to the amount of organic matter consumed by fire, and it is often misused to describe a broad range of impacts caused by fire (Keeley 2009).  Fire intensity and severity are strongly correlated aboveground but weakly correlated belowground. Fire severity in soils is generally defined as the degree to which soil organic matter is consumed or mineralized as a consequence of fire, particularly within the forest floor and upper mineral soil horizons.

Fire burns organic matter and releases carbon dioxide into the atmosphere, along with other greenhouse gases such as methane and nitrous oxide, reducing ecosystem carbon stocks and increasing climate change.