Studies question wisdom of thinning forests to stop fires

Wednesday, April 15, 2015

Originally published at: 

In 2011, a downed power line sparked the massive Las Conchas wildfire that roared through homes and scorched 156,000 acres of forest in the Jemez Mountains. And that was just the beginning of the damage. In the weeks that followed, rains washed tons of ash and sediment off the blistered slopes into the Rio Grande, forcing the city of Santa Fe to shut down a river diversion system for six weeks.

The fire’s impact on a major Santa Fe drinking water source is a big reason city officials are now considering joining a collaborative brought together by The Nature Conservancy to thin and burn thousands of acres over the next 20 years in mountain ranges that drain water into the Rio Grande. The partnership hopes the plan will reduce the kind of catastrophic wildfires that wreaked havoc in the West over the last several years.

“Our interest is managing the watershed for water quality,” said Rick Carpenter, the city’s source of supply manager.

But as city officials consider joining the group, known as the Rio Grande Fire and Water Source Protection Collaborative, the science is still changing. New studies question how, and where, fire and tree thinning in Western forests should be used to restore forest health and protect watersheds. The studies, and the move toward treating forests across large landscapes, are fueling some old debates over the best way for people to manage forests that have been dramatically altered during decades of fire suppression, logging and overgrazing.

One such study by a team of 11 scientists from Canada and the United States, published in 2014 in the Public Library of Science, found that long before human intervention, a mix of fires of low, medium and high intensity in Western ponderosa pine and mixed-conifier forests were more common than previously believed.

Citing such studies, Jan Boyer and Arthur Firstenberg of the Santa Fe-based Once A Forest are among those who vehemently oppose prescribed burns and thinning any old-growth trees.

They believe allowing fires to burn and setting prescribed fires add to climate change by adding carbon to the air. “Save every tree you can because it is absorbing carbon and storing all the carbon it encountered in its lifetime,” Boyer said.

To be sure, forests are a tough and complicated resource to manage. Decisions are colored by politics, tradition, economics, public fears and ecology.

In general, foresters and fire ecologists believe more fire on the ground and some thinning are the best option for helping forests survive the megadroughts and warmer temperatures predicted by climate models for the Western United States.

The official policy of the U.S. Forest Service recognizes the benefits of fire in forests and advocates actively guiding fires without just stomping them out. Still, the Forest Service “continues to aggressively suppress 98 percent of fires regardless of whether they were ignited by people or nature, at a cost of more than $1.5 billion a year,” said Timothy Ingalsbee, a former firefighter and head of the Oregon-based Firefighters United for Safety, Ethics and Ecology.

The exception to all-out suppression is in the Southwest, which is leading the country in using fire to help forests, Ingalsbee said.

Carpenter thinks joining The Nature Conservancy group, which has 29 government, nonprofit and private landowners so far, will give the city a better position to work with other agencies on projects that will help protect local water supplies. The collaborative has representatives from local, state and federal agencies, land grants, river restoration and environmental groups. Organizers are hoping pueblos and tribes along the Rio Grande also will join the group.

“We have a vision that people can play a role in helping forests and watersheds be more resilient to wildfires and higher temperatures based on a scientific foundation,” said Laura McCarthy, director of government relations for The Nature Conservancy in New Mexico.

Saving water, money

The collaborative will focus on reducing wildfire risks and maintaining watersheds in the Sandia and Manzano Mountains, the Jemez Mountains, the San Juan and Chama rivers and on the western slope of the Sangre de Cristo Mountains.

Scientists have modeled debris flow following fires in the Central New Mexico mountains and mapped the density of forests. They believe about 30,000 acres of forests a year need to be treated to begin changing fire behavior in the mountains, according to information from The Nature Conservancy.

Bill Armstrong, longtime fire ecologist for the Santa Fe National Forest, puts the estimate higher. “By my calculations, we need to be burning between 40,000 and 60,000 acres a year over the next 10 years just to accomplish a first entry into the fire-dependent vegetation types on this forest,” he said.

McCarthy said treating the forests to reduce the intensity and size of fires will ultimately save money. Thinning forests costs less than half the price of damage from wildfires, according to The Nature Conservancy.

The 2011 Las Conchas Fire cost an estimated $246 million in suppression costs and lost property. The total cost of the 20- year plan to treat forests in the four mountain ranges is estimated at about $420 million, according to The Nature Conservancy.

Even those who think prescribed burns and thinning can help forests say it depends a lot on where the work is focused. One such person, Bryan Bird with the nonprofit group WildEarth Guardians, believes the best place to put money is on projects to prepare communities for fires and floods.

“Fire and flooding are inevitable. It will happen. We can only have minute influences,” he said. “We can fireproof our communities, but we cannot fireproof our forests, especially in light of drought and climate change.”

Roller-coaster fire policies

Collaborative efforts like the one promoted by The Nature Conservancy to restore and maintain forest health across whole mountain ranges are catching on. A two-decade-long joint effort by the city of Santa Fe and the Santa Fe National Forest to reduce fire hazards and maintain the watershed feeding two municipal reservoirs was among the first. More recently, the Santa Fe National Forest, Valles Caldera National Preserve and several groups are working to restore natural cycles of fire in the Jemez Mountains.

But a century ago, forest managers saw fire only as a threat to put out. In the late 1800s and early 1900s, drought-stricken Michigan, Wisconsin, South Carolina and Washington each had megafires that burned between 1 million and 3 million acres and killed almost 2,000 people. Then in 1910, a few years after the U.S. Forest Service was established, fires raced across 3 million acres of forest lands in Idaho and Montana, killing 85 people. Firefighters called it the Big Blowup, and it changed fire policy. Total fire suppression became embedded in Forest Service culture, according to the Forest History Society.

Even back then, forest and fire ecologists knew fire played an important historical role in Western forests. Ponderosa pine forests in the Southwest had ground fires come through every decade or less, burning off grasses, brush and small trees without harming the larger trees. Hotter fires that killed and replaced whole stands of mixed conifer and higher elevation forests occurred less frequently, every few hundred years. Some trees, wildlife and birds depended on post-fire landscapes for their survival.

As fire was suppressed, the role wildfires had played in keeping forests healthy for thousands of years ended. Pine needles that normally would have burned off piled up for decades. Logging and livestock grazing further changed forest structure.

By the 1990s, the Forest Service policy shifted back to fire as a tool. Forest managers were encouraged to let fires burn where they could help forests and did not endanger communities or other resources.

The Southwest had been in a two-decade wet period that helped dampen fires, but that ended in 1996, said Craig Allen, a scientist who has studied forest and fire ecology in the Jemez Mountains for decades.

The changes in forests brought by decades of fire suppression, logging and grazing met up with drought. And New Mexico mountains began to burn in a way they hadn’t for more almost a century.

By the time the fires began to burn, more people had built homes in the forests and many were ill designed to withstand fire.

Faced with millions of acres of forests they now thought were overgrown and prone to major fires, and more people living near those forests, the Forest Service ramped up prescribed burns. But when one set in Bandelier National Monument led to the Cerro Grande Fire in 2000 that burned 47,000 acres and destroyed more than 200 Los Alamos homes, planned burns got a black eye.

Fire officials have allayed many of those fears. Los Alamos has regular prescribed burns now in the canyons below the town and inside the town. The city of Santa Fe and the Forest Service have periodic burns in the municipal watershed. And the collaboration in the Valles Caldera National Preserve has conducted several thinning and prescribed burn projects.

But there’s still pushback.

Different opinions

Firstenberg of Once A Forest said while it is impossible to stop all fires, the Forest Service should return to the old policy of stopping as many fires as possible. “The only intelligent response is to put out the ones we can, not to go around intentionally burning,” Firstenberg said.

But fire suppression ignores the historical role fires have played in many Western forests and the role it can play again in helping forests survive climate change, Allen said.

Fire’s role in forests varies depending on the mountain ranges, types of trees and drought.

Allen said decades of studies in the Jemez Mountains show ponderosa pine forests had adapted to the low-intensity ground fires that rolled through every decade or so until they were stopped beginning in the early 1900s. There were a few high-intensity fires — the crown fires that kill everything in their path — but they were only a few acres and less frequent, Allen said.

The Sangre de Cristos east of the Jemez also had frequent low-intensity fires in the ponderosa pine forests. Every few hundred years, much larger, hotter fires in the high elevations burned out forests of one species and replaced it with another.

“The last stand-replacing fire in the Pecos Wilderness [above the Santa Fe’s municipal watershed] was 1695,” Allen said. “It’s due for another one.”

While even The Nature Conservancy talks about how much larger fires have become in the last few decades, that isn’t the biggest issue, Allen said. “We know there were many big fires burning before the 19th century. In 1748, for example, most of the mountain ranges in the Southwest had fires burning on them.”

The problem is big fires now are burning hotter across more acres now than before, wiping out forests and seed banks that were only adapted to low-intensity fires. The fires are so hot, trees aren’t growing back the way they once would have after fire.

Collaborative projects like those in the Jemez Mountains are important to help fire return to the landscape without wiping out everything in its path, Allen said.

Paul Davis, former manager of Sandia National Laboratories’ Environmental Risk and Decision Analysis Department, is skeptical of the burn and thin approach. He believes putting any money into prescribed burning and thinning fails to address the cause of most forest fires: people. Las Conchas and Cerro Grande, the two largest fires in the Jemez Mountains since 2000, were both human-caused.

“The key is to not let humans start fires in the first place,” said Davis, who runs a consulting business now called EcoLogic. “It would be cheaper for them to buy every house that burns, instead of spending money on this.”

Davis is more than a little jaded about the ability of the Forest Service to manage fires. His house was one of six that burned down during the 2008 Big Springs Fire in the Manzano Mountains, a circumstance he blames on a back-burn set by the Forest Service to help fight the wildfire.

Davis said he’s read through The Nature Conservancy’s Rio Grande forest restoration plan and finds many problems.

He said its “fatal flaw” is not analyzing by how much the projects will reduce wildfire risks to water supplies. “When you are asking people to spend this kind of money, you should know what you are getting for your money, and here you should be getting a reduction in risk,” Davis said.

The Nature Conservancy believes there is plenty of hard evidence that prescribed burning and thinning mitigate wildfires and protect water sources. They point to research from the U.S. Geological Survey, NASA and insurance companies that predict wildfires will only get hotter and more destructive in the years ahead.

“We created a comprehensive plan, which is a living document and, as such, will evolve and be modified as new studies are completed,” said Tracey Stone of The Nature Conservancy. “With the state’s fire history, research and information we have now, we wanted to provide a blueprint for moving forward.”