MOUNT DIABLO -- A recent wildfire that blackened 3,100 acres has sparked debate about a state decision 24 years ago to end most cattle grazing in ¿this big state park on a mountain surrounded by suburbs.

It also has spurred discussion about bringing controlled burns back to the area, which hasn't seen them for about 15 years.

Some Mount Diablo neighbors contend the Morgan Fire, which started Sept. 8 and took six days to put out, would have been smaller and less intense had the California park system not decided in 1989 to slash grazing in the 20,000-acre Mt. Diablo State Park. State officials wanted the park to retain a more natural state and also sought to protect its rich community of rare plants and animals, including the Alameda whipsnake.

Bulldozers work on creating a fire break as fire from a 3,700-acre vegetation fire burns off of Curry Canyon Road on the southeast side of Mt. Diablo in
Bulldozers work on creating a fire break as fire from a 3,700-acre vegetation fire burns off of Curry Canyon Road on the southeast side of Mt. Diablo in unincorporated Contra Costa County, Calif., on Monday, Sept. 9, 2013. The fire began Sunday near the corner of Morgan Territory and Marsh Creek roads. (Jose Carlos Fajardo/Bay Area News Group)

Critics say the lack of grazing in the park allows tall grasses to build up, accelerating the spread and intensity of wildfires.

Former Clayton Mayor Pete Laurence said the Morgan Fire shows the need to bring more cows back to the park to graze in areas near the thousands of homes in such communities as Clayton, Walnut Creek, Danville, Blackhawk and Alamo.

"Clayton is at real risk; it's not a hypothetical risk," Laurence said.

Julie Pierce, the current Clayton mayor, says grazing can help knock down tall grasses and create a safety boundary for homes. Her city has been pleading with the state for years to resume grazing.

"Maybe we have to get out those old letters and say, 'See, we told you so,'" Pierce said.

Meanwhile, the California Cattlemen's Association is drawing up a proposal to present to state officials to start, resume or expand grazing in a few state parks, including on Mount Diablo. The group already was considering the move, but the Morgan Fire intensified interest in the proposal.

Tim Koopmann, a Sunol rancher and president of the association, said well-managed grazing in grasslands can knock down fire fuel and enhance habitat for some rare species.

"The overall trend in California is toward increased grazing on public lands as people realize grazing can be good for the environment," Koopmann said.

State park and fire officials, however, say they don't see evidence that the Morgan Fire would have burned differently had more than token grazing been allowed on Mount Diablo. The blaze, started on private land by someone target shooting on a hot day, burned no houses but threatened 75 rural homes on the east side of the mountain. Fighting the fire cost about $4.5 million.

The wildfire burned mostly in steep areas of brush, trees and chaparral -- higher up on the mountain than the lower grasslands where cattle would graze, said Cal Fire Battalion Chief Mike Marcucci.

"I don't think anyone has done the research to say definitely if more grazing would have changed this fire," Marcucci said. "But most of what burned was brush, not grass."

The Morgan Fire started on private land with brush and quickly spread to steep park areas with trees and thick brush, said Marcucci, who supervises firefighters at a Marsh Creek Road fire station near the site of the blaze.

Firefighters in their initial response thought they had stopped the fire soon after it broke out. Pine cones from a burned tree, however, exploded and threw hot embers hundreds of feet, touching off flames that raced up the mountain, Marcucci said.

Seth Adams of the Save Mount Diablo conservation group is convinced that the reduced grazing had little or no effect on the Morgan Fire.

Major wildfires erupted on Mount Diablo about every 30 or 40 years back when large-scale grazing was allowed, he noted. A fire in 1977 burned 6,000 acres there.

"The mountain has evolved with wildfires," Adams said.

In 1989, the state cut back grazing from more than 7,000 acres in the park to a mere 1,000 or fewer acres in the Macedo Ranch area near Alamo.

In response to heightened fire safety concerns, state park officials developed a wildfire management plan to clear, mow and spray grass and brush in selected areas along roads, park borders and fire breaks.

The park has allowed a small cattle herd in the Macedo Ranch section of park as a nod to the area's ranching heritage.

"We have kept up with the plan," said Dan Stefanisko, the Mount Diablo park supervising ranger.

State park officials, however, say it has been about 15 years since one part of that plan -- controlled burns to reduce grass and brush -- has been carried out.

As a result of the Morgan Fire, Stefanisko said state officials will look more closely at bringing back controlled burns to Mt. Diablo State Park. There have been fewer such burns on state properties throughout California, officials said, because of air quality restrictions and high supervision costs.

Any proposal for controlled burns on Mount Diablo would be considered carefully to make sure the burn wouldn't harm rare species such as the threatened Alameda whipsnake, said Cyndy Shafer, a state senior environmental scientist. "We're not going to rush into it," she said.

Jim Bone, a longtime Clayton resident who housed firefighters on his ranch during the fire last month, said cattle grazing is a better option than controlled burns.

"Controlled burns cost a lot of money; the cattle eat for free," Bone said.

Walnut Creek rancher Tom Brumleve said he and other ranchers have measured grass density on Mount Diablo and found it's 20 times more dense in ungrazed areas than in grazed ones.

"You can't graze all places," said Brumleve, a Mount Diablo resident whose cattle were booted out of the state park after the 1989 decision. "But I think the fire wouldn't have been as severe if the park had more grazing."

Koopmann, a Sunol rancher, said he worries oak trees on Mount Diablo may have suffered worse damage in the Morgan Fire because grass buildup typically produces hotter flames for longer periods under trees. State officials say no survey of oak tree damage from the fire has been done.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff. Contact Elisabeth Nardi at 925-952-2617. Follow her at Twitter.com/enardi10.