Ecological disturbance represents a kind of natural change that occurs instantaneously and unpredictably, killing many plants and animals. Fire is one of many kinds of natural disturbance events, all of which vary widely in severity and extent. Importantly, only the more severe forms of disturbance allow for the process of plant succession to take place. A succession of different plant and animal species, in turn, promotes the coexistence of many species on Earth. Severe fire is an especially interesting agent of natural disturbance because it leaves blackened, standing-dead trees in its wake. Thus, severe fire disturbance initiates a special kind of succession that can be found following no other form of physical disturbance. Many plant and animal species that occur in recently burned conifer forest conditions do not appear following any other kind of severe disturbance.