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Old brush fueling Sierra Nevada fire

SACRAMENTO — Unnaturally long intervals between wildfires and years of drought primed the Sierra Nevada for the explosive conflagration chewing up the landscape on the edge of Yosemite National Park, forestry experts say.

The fire had ravaged 282 square miles by Tuesday, making it among the largest on record in California history.

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Containment increased to 20 percent, but the number of destroyed structures rose to 101 and some 4,500 structures remained threatened. Firefighters were making stands in several mountain towns.

Federal forest ecologists say that historic policies of fire suppression to protect Sierra timber interests left a century’s worth of fuel in the fire’s path.

The Rim Fire’s exponential growth slowed only after hitting areas that had burned in the past two decades, which officials said shows the utility of prescribed and natural burns that clear brush, and allow wildfires to move rapidly without killing trees.

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