Before the 1970's, the policy of the Park Service had been to fight natural fires.

Everywhere, try to let moderate natural fires run their course.

Whatever fire de- stroyed such a large town, it was not natural fire.

The effect was anomalous, since no sea monster had natural fire.

But also there was a sudden crackling, a flash of heat, as if no natural fire had been laid and waiting.

"Obviously this was anything but a natural fire," Zerft observed.

Left to themselves, they are subject to natural fire which rejuvenates the ecosystem.

Human suppression of natural fire has greatly reduced their numbers.

In the remaining 75 percent of Yosemite, natural fires are allowed to burn themselves out.

Since the late 1970s, some 300 natural fires have been allowed to burn themselves out.