Conceptual figure illustrates the impacts of fire exclusion and suppression on area burned and fire severity

Prior to about 1880, traditional burning and lightning-ignited fires acted as stabilizing feedback in forests. Fires were low severity but frequent and burned large areas, maintaining low fuel loads. The onset of sustained fire exclusion and suppression over many decades reduced annual area burned, reflected by a decline in tree-ring fire scars, during which time fuel loads accumulated. At present, fires generally burn during pronounced droughts, increasing the area burned in recent years, although total area burned remains below historical levels. These fires are considered destabilizing feedback in forests, as they lead to reduced forest recovery relative to historical fires. The future is uncertain and depends on a variety of factors, including management practices, social priorities, and drought severity. 

This conceptual model generally applies to dry conifer forests in western North America, formerly red pine dominated forests in the southeastern boreal forest, and temperate broadleaf and conifer woodlands and forests of the eastern United States. Figure credit: Jessie Thoreson. For full caption, see Parks and others (2025).