Like most of California and the West, San Luis Obispo County faces a severe wildfire danger.
Much of the county is covered with highly flammable chaparral. Increasingly, land managers are turning to the use of prescribed fire as a way to reduce this fire danger and achieve a variety of environmental goals.
But the technique is fraught with both promise and peril.
A good example is a burn conducted late last year by Cal Fire and PG&E. They used torches slung beneath helicopters to ignite a spectacular prescribed fire in the rugged hills just south of Montaña de Oro State Park.
The purpose of the burn was to remove the dense tangle of brush blanketing the hillsides and help a scarce stand of bishop pines regenerate. It was the third prescribed burn conducted in the area since 2009 and the results thus far had been excellent.
But this burn did not go as planned.
Winds shifted unexpectedly and began to blow down Coon Creek. At a bend in the creek, embers blew across and the fire spread to the north side of the canyon, into the state park and outside the planned fire boundaries.
When the flames were extinguished, some 130 unplanned acres of parkland had burned. The agencies had dodged a bullet; no one was hurt and only scrubland had burned.
“That area probably would have been treated by fire anyway sometime in the future,” said Alan Peters, Cal Fire unit forester who planned the burn. “We are continuing to monitor, but there haven’t been any negative impacts, yet.”
But land managers were forced to make adjustments to avoid other potentially costly escapes in the future.
“We are using additional firefighting resources on prescribed burns now,” Peters said “In some cases, the resources are now doubled.”
Prescribed fire is one of several techniques available to reduce the fire danger. Others include brush clearing with hand crews, bulldozers, goats and mechanical grinders called masticators. These are typically used to clear brush near homes or to create fuel breaks along ridge tops.
However, prescribed burning has distinct advantages that other techniques don’t, putting it in a class by itself. Cost is the main one, Peters said.
Fire is the cheapest way to treat large areas because it essentially does not cost any money. It’s just a matter of allocating existing personnel and resources to do the job.
“If we burn 1,000 acres or we don’t, our budget doesn’t change,” Peters said. “Conversely, it would cost more than $1 million to masticate the same area.”
In recent years, PG&E’s lands north of Diablo Canyon nuclear power plant have become a showcase for prescribed fire. It started in January 2007 when a wild fire burned 300 acres north of the plant in what would be known as the Diablo Fire.
It was a big wakeup call for firefighters, Peters said. If a fire had started in that same area in the summer, it could have been pushed along by prevailing northwesterly winds and burned as far as Prefumo Canyon and the outskirts of San Luis Obispo.
PG&E and Cal Fire began a program of prescribed burns in late fall and early winter. To date, 1,228 acres have been treated with another 273 acres planned for burning this winter in the Spooner Creek area, on PG&E land north of Diablo Canyon.
The basic idea behind prescribed burning is to remove fire fuels during times when a fire will burn cooler and more predictably. This reduces the chances that a catastrophic wildfire will occur.
If a wildfire does occur, firefighters will try to herd it into a recently burned area where it will go out due to lack of fuel before it reaches homes. A properly executed prescribed burn will reduce fuel loading by three quarters, said Phil Veneris, Cal Fire battalion chief in Los Osos.
Ideally, a wild landscape would have a patchwork or mosaic of old growth and more recently burned areas. This gives wildlife a maximum diversity of habitat types and firefighters places to make a stand.
Bishop pines need fire
The PG&E lands north of Diablo Canyon are ideal for prescribed fire for another reason. Many of the ridge tops are covered with bishop pine forests.
Bishop pines are dependent on fire to reproduce. Their cones require the heat of fire to open and disperse their seeds. Fire also clears the forest floor of brush and pine needles, allowing the newly released seeds to reach the soil and germinate.
Foresters estimate that at least 60 percent of bishop pine forest must burn to get good regeneration. Forests in that area have not burned in about 80 years, which is about as long as a bishop pine lives.
In these unburned areas, old bishop pine trees protrude from an impenetrable hip-high blanket of coffeeberry, chinquapin and other shrubs hugging the ground. The bark of many of the pines is coated with rivulets of sap where the trees tried to pitch out invasive insects or fight off pine pitch canker, a fatal fungal disease.
“People look at an area like this and see a lush green forest, but it’s a forest that is nearing the end of its lifecycle,” Veneris said.
Standing nearby in stark contrast to this old growth zone are areas where a prescribed burn occurred less than a year ago. PG&E biologist Sally Krenn walks through the burn area and points out the changes that have occurred in that short time.
The landscape is dotted with burned skeletons of large manzanita bushes and pine trees, their cones wide open. Patches of grass have grown in the blackened earth and are being replaced by clumps of lupine and bracken fern.
Black sage and other chaparral species are already beginning to take over, and many of the manzanita skeletons are starting to re-sprout at their bases. More importantly, the landscape is dotted with bishop pine saplings. Within 15 to 20 years, the area will again be a lush pine forest, Krenn said.
“Prescribed burning also has the added effect of adding nutrients to the soil,” she said.
Burning has some critics
Not everyone is a fan of prescribed burning, however. One of the most vocal critics is Richard Halsey, executive director of the California Chaparral Institute, a nonprofit organization based in San Diego County that promotes the understanding of California's chaparral ecosystems.
He thinks fire agencies should spend their time and money protecting vulnerable communities by surrounding them with fire breaks and making sure homes are fire safe. The natural frequency of fire in a place like San Luis Obispo County is low, he said.
Brush will get thick naturally, and that’s the way it’s supposed to be. Prescribed burning does not reduce the fire danger and just lets in weeds, he argues.
“A lot of it has more to do with budgets and careers than what is beneficial for the ecosystem,” he said. “Generally speaking, the way it has been used in the past, it’s not the most effective way to protect life and property.”
In spite of its popularity with firefighters, prescribed fire is not without its problems. There’s always the chance that the fire could escape and destroy property.
One of the worst instances of a disastrous prescribed burn took place in 2000 in New Mexico. A prescribed fire near Los Alamos escaped and burned several hundred homes and other buildings.
Air pollution control officials and people living near a prescribed burn also have their concerns. They prefer windy days when the smoke is quickly dispersed. But high wind increases the chances that the fire will escape, so a compromise must be worked out.
As a result, a prescribed burn can take months to set up. Many agencies and groups must sign off on it. Forester Peters said an inch-thick sheaf of environmental documents is necessary to set up a typical prescribed burn.
Prescribed burns can also be unsightly. Burned areas stay blackened for several years following a fire, a condition that is unpopular with hikers.
However, fire managers remain committed to prescribed burning. They argue that prescribed fire is an effective way to reduce the intensity of catastrophic forest fires such as the recent Rim Fire in the Stanislaus National Forest and Yosemite National Park.
San Luis Obispo County has not had a large wildfire since the August 1994 Highway 41 fire that burned 48,531 acres and 42 homes from Toro Creek to Lopez Canyon. The systematic use of prescribed fire could reduce the chances of another such fire, fire managers say.
“We’ve burned only about 4,000 acres statewide this year,” Peters said. “That’s far less than a drop in the bucket.”
Prescribed burns planned
Cal Fire’s priorities change depending on weather and available resources, but here’s a look at the agency’s plans for prescribed burns — in the order they’d be conducted — between now and mid-December:
- State Parks (Harmony Headlands, Estero Bluffs, Molinari). These three areas total about 300 acres of habitat improvement/biological restoration
- Coon Creek: about 19 acres near Pt. Buchon
- Lewis: about 700 acres off Pozo Road near the La Panza Fire Station
- Pismo: about 186 acres one mile north of Pismo Beach
- Spooner Peak: about 273 acres just north of Diablo Canyon nuclear power plant
Areas of highest fire risk
Large shrublands scattered throughout the county are probably at the highest risk for a large wildfire, due to the ongoing drought and record dry vegetation.
Areas dominated by grasses, such as in the northern and eastern areas of the county, are less vulnerable due to sparse grass growth and livestock, which reduce the fire hazard by eating the grass.
High hazard areas due to heavy grasses, record dry vegetation and difficult topography include Irish Hills, Parkhill, East and West Cuesta Ridge, Cambria, the Santa Rita Road corridor, Suey Creek, Nacimiento basin, West Atascadero, Pozo, Huasna, and East Arroyo Grande.
Source: Alan Peters, Cal Fire unit forester