Fire can kill all or part of individual plants, as well as animals that are unable to escape. Fire is unique among disturbances in that its intensity and frequency depend upon the growth rate of the vegetation that is burned. The accumulation of plant material that serves as fuel produces an inverse relationship between fire frequency and fire intensity. Thus, the properties of any individual fire or fire regime are influenced by plant growth rates, climate, weather, and sources of ignition. Fire has many properties in common with other mortality-causing disturbances, such as floods, windstorms, and logging. The confusing variability in ecological responses to fire can be clarified by appropriate classification of the environments in which fire occurs. Ecological theory makes specific predictions about the interaction of disturbance mortality with the rates at which populations recover from disturbance. The effects of disturbance on species diversity can differ greatly between environments that differ in soil properties, climate, and other factors that influence the growth rates of individuals and populations of plants. Accumulating data support the theoretical prediction that the effect of disturbance on diversity should reverse between productive and unproductive environments. In unproductive environments, where populations grow and recover slowly, an increase in the frequency of disturbance generally produces a decrease in species diversity. In contrast, in productive environments, an increase in disturbance frequency often produces an increase in species diversity. The ecosystems of south-west Western Australia, Australia, vary greatly in their productivity and characteristic disturbance regimes. Consequently, the effects of a particular frequency and intensity of fire are likely to vary significantly, or even reverse, among these ecosystems. Classification of Western Australian ecosystems in terms of plant productivity and fire frequency should provide useful insights into the effects of alternative fire management plans on the diversity of various types of plants and animals. © 2003 Buckhuys Publishers, Leiden, The Netherlands.