Sept 1 (Reuters) - A cluster of controlled fire and tree-thinning projects approved by forestry officials but never funded might have slowed the progress of the massive Rim Fire in California, a wide range of critics said this weekend.

The massive blaze at the edge of Yosemite National Park in the Sierra Nevada mountains has scorched an area larger than many U.S. cities - with some of that land in the very location pinpointed by the U.S. Forest service for eight projects aimed at clearing and burning brush and small trees that help fuel wildfire.

The projects, which were approved by the U.S. Forest Service but never funded by Congress, would have thinned the woods in about 25 square miles (65 square km) in the Groveland District of the Stanislaus National Forest, much of which was incinerated by the Rim Fire.

About 9,000 acres (3,642 hectares) were suitable to be deliberately burned as fire prevention buffer zones in 2012, the Forest Service said in a document provided to Reuters.

But reductions in funding for fire prevention efforts by Congress in recent years coupled with stringent air quality standards that limit the timeframe for such burns have hampered efforts to carry them out on a larger scale.

Last year, the Forest Service had funding to burn 449 acres (182 hectares) in the Groveland District but did not reach that target, said District Ranger Maggie Dowd.

The wildfire is the sixth-largest on record in California. It burned over 220,000 acres (89,000 hectares) over the past two weeks while penetrating Yosemite National Park and threatening to befoul the Hetch Hetchy reservoir providing the lion’s share of water to San Francisco.

“This is a colossal unfunded backlog of critically important fuel reduction work,” said John Buckley, executive director of the Central Sierra Environmental Resource Center and a former Forest Service fire fighter. The projects “would have inarguably made the Rim Fire far easier to contain, far less expensive and possibly not even a major disaster.”

Over the past several years, wildfires in the U.S. West have become increasingly frequent and at times deadly. Earlier this year, 19 firefighters were killed in a blaze in Arizona, and wildfires have raged in several states, including Nevada, Alaska and New Mexico.

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Federal fire figures show an average of 7.6 million acres (3.1 million hectares) charred per year between 2004 and 2012, up from 3.6 million acres (1.46 million hectares) annually in the preceding 20 years.

Part of the problem, experts and many fire officials say, is that funding has been low for the controlled burns and forest-thinning work that makes it harder for a wildfire to spread.

In recent years, Jarvis said, the trend has been to shift money from fire prevention to firefighting.

“We’ve got to invest up front in terms of controlling and managing these fires,” said Jonathan Jarvis, director of the National Park Service from his smoke-filled post in Yosemite National Park. “Just waiting for the big fire and then throwing everything you’ve got at it makes no sense.”

The massive blazes are fueled by high temperatures, said U.S. Forest Service geographer Carl Skinner.

Mike Albrecht, co-owner of the logging company Sierra Resource Management, which operates on public land in the Sierra Nevada mountains said that the backlogged projects would likely have helped limit the Rim Fire.

The “one-two punch” of thinning the forest through logging and prescribed burns is essential for stemming the tide of catastrophic wildfires across the American West, he said.

Craig Thomas, conservation director for the environmental coalition group Sierra Forest Legacy, said such a course would help reduce the intensity of wildfires enough to spare the largest trees, while clearing space and providing nutrients for grasses and wildflowers.

In addition to perennial funding shortfalls for prevention efforts, Thomas faults federal and state air quality regimes that limit the timeframe for prescribed burns by counting the smoke they generate along with industrial and auto emissions - while not counting the smoke from an actual wildfire.

There is also skepticism over the relative importance of planned burning among some lawmakers, including Congressman Tom McClintock, a third-term conservative Republican in whose district the Rim Fire has burned.

More dire than a backlog of Forest Service controlled burns, McClintock says, is the precipitous, 25-year decline in logging of bigger, money-making trees on public lands.

“If we were harvesting the same amount of timber we once did, we’d have fewer fires but also a revenue stream for the treatment of many thousands of acres (hectares) that we’re not treating today,” he said.

Dowd, the Forest Service Ranger, said that with containment lines built around less than half of the still-burning Rim Fire, it is too early to know how much the prevention projects might have helped.

But she said that the several dozen acres of prescribed burns carried out in her district over the past two years, are insufficient.

“It’s not enough,” Dowd said.