Earth and Sky科普英語：Fire Regime 火

Fire was a creation of life -- born from oxygen and organic matter -- ignited by lightning. Thus fire has been a fundamental feature of the Earth for at least 400 million years. A scientist talks about fire -- today on Earth and Sky.

JB: This is Earth and Sky, speaking with fire expert Steve Pyne, in the Biology and Society program at Arizona State University in Tempe.

Steve Pyne: Fire looks the way it does on Earth today because of what people have done and not done, the ways we've started fires, the ways we've stopped them, or tried to stop them, the ways we've moved fuel around. That is to say, we create fuel and can put in fire where it would not naturally occur or under different rhythms or patterns, what you would call regimes.

JB: The "fire regime" is a concept Dr. Pyne uses to describe the range of fire.

Steve Pyne: It describes the pattern of fire that appears on the land. So that it may refer to the typical frequency of the fire, the seasonal timing of the fires, the intensity of the fires, the geographic size of the fires. In other words, fire appears in particular ways. And if you look at the ways that it appears, then you can begin describing a fire regime in the same way you can think of a precipitation regime.... And individual fires appear within a regime much like individual storms do within a climate.

JB: More -- tomorrow. Our thanks today to the Bureau of Land Management and to the National Fish and Wildlife Foundation -- supporting the conservation of native fish, wildlife, plants and their habitats. I'm Joel Block for Earth and Sky.