The Associated Press

AP Photo/Ross D. Franklin A wildfire burns near Crown King, Ariz., last month.

PHOENIX — As a wildfire bore down on a mountain community north of Phoenix late last month, the town was protected in part by fires intentionally set in previous years.

Intentional burning around the historic mining town of Crown King had cleared away brush and trees that serve as fuel for wildfires. Though a small number of homes and buildings were destroyed in last month's wildfire, fire crews said losses would have been worse had they not burned away parts of the forest.

"Our success rate would have been dramatically reduced," said Jason Clawson, a fire management officer who supervised the planned burning of 2 square miles around Crown King in 2005-2007.

But prescribed burns draw the ire of some residents who complain about smoke, blackened forest and the possibility that crews could lose control of the fires.

A fire set by park officials in 2000 to eliminate overgrowth near Los Alamos, N.M., was driven out of control by winds, burning nearly 67 square miles and more than 200 structures.

Federal and state agencies have intentionally burned an average of 3,750 square miles of land in each of the last eight years, according to the National Interagency Fire Center in Boise, Idaho.

From a firefighting standpoint, intentional burning removes overgrowth on the ground so it doesn't heat up trees and spark crown fires, powerful blazes that burn on treetops and spread rapidly.

Prescribed burns carry benefits other than mitigating wildfires. They can help restore animal habitat that has little food because thick overgrowth blocks light from reaching low-growing plants.

They also can help strengthen watersheds by removing spindly trees that consume water. Once those trees are gone, rainwater can get into the watershed to help fish, rather than being sucked up by overgrowth, said Ken Frederick, a spokesman for the fire center.

With limited firefighting budgets, state officials said prescribed burns are cheaper than using machines and people to clear brush. But intentional fires are riskier, winds might blow embers beyond protection lines, flaming dead trees could fall outside boundaries, and smoldering debris such as pine cones might roll out of targeted areas.

No figures were available on the number of prescribed fires that burn out of control, but officials said they are rare.

Before starting an intentional blaze, fire managers evaluate weather conditions and the area of forest that will be burned and make sure they have enough people to monitor it so they can stamp out any embers that go beyond protection lines.

Fire managers said they seek environmental permits to do the burning and meet with residents to explain the benefits of the intentional fires.

The vast majority people living around forested areas understand the need to eliminate forest fuels around their homes, said Kirk Rowdabaugh, Arizona's state forester.

"There is more public tolerance than you'd expect," he said.