Fire regimes are sets of recurring conditions of fire that characterize given ecosystems. Those conditions include a specific range of frequency, fire behavior, burn severity, timing of burn, and size/pattern of burn. Eliminate fire, increase fire, or alter one or more of the components of a fire regime beyond the range of variability for a given ecosystem and that ecosystem will change to something else—habitats, species, and resources/services will be lost; climates may change; and fires may become persistent, pervasive and/or catastrophic.

Throughout the world, the alteration of fire regimes is a significant threat to biodiversity and human livelihoods regardless of whether the affected ecosystems are fire-maintained or fire-sensitive. In the tropics, broadleaved forests are generally regarded as fire-sensitive, while many tropical environments support highly significant ecosystems that depend on fire. Recent devastating fires in tropical broadleaved forests in Indonesia, Mexico, West Africa, Central America and the Amazon Basin--where fire normally would play a limited ecological role--and in fire-prone temperate forests in the United States and Australia, that have been subjected to effective fire exclusion, have highlighted the need for 1) a better understanding of fire’s ecological role and the implications of altering historic fire regimes, 2) assessments of, and approaches to, the socio-economic roots of fire, and 3) the development and implementation of more appropriate responses to fire when they occur.