Love That (Controlled) Smoke

Prescribed burns good for the planet, health of residents


Controlled burns like this one near Payson put 18 percent to 60 percent less carbon into the air than a much hotter, uncontrolled wildfire, a new study says.

Controlled burns like this one near Payson put 18 percent to 60 percent less carbon into the air than a much hotter, uncontrolled wildfire, a new study says. |

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As Rim Country heads into the prime season for controlled burns, a recent study has produced some surprising good news.

Turns out, controlled burns during the damp fall season that reduce the fire danger to Rim Country communities, also put less smoke and carbon dioxide into the air than wildfires, according to a study by the National Center for Atmospheric Research.

In fact, widespread use of controlled burns would reduce carbon dioxide emissions in the West by 18 percent to 25 percent — and perhaps as much as 60 percent in especially fire-prone areas like Rim Country.

The key to the seemingly counter-intuitive finding lies in the fate of the big trees — which generally survive low-intensity controlled burns but not run-away wildfires, like the 600,000-acre Rodeo-Chediski Fire.

That massive blaze that nearly consumed Show Low and cost some $60 million to fight, transformed the U.S. Forest Service’s approach to fires in Rim Country. The Tonto National Forest has been scrambling ever since to thin a buffer zone in the thick, overgrown, tinder-dry forest surrounding Payson, Pine, Strawberry, Star Valley and other Rim communities.

Contractors generally thin the surrounding forest, cutting down and piling up about 80 percent of the trees and brush. They then come back and set those piles on fire in the fall, when the high moisture content of the fuels makes it possible to keep the controlled burns from spreading. Increasingly, the Forest Service is also turning wildfires into controlled burns, but letting them keep on burning when conditions allow.

Once the Forest Service has created adequate buffer zones, forest managers hope to start using more controlled burns without the initial hand thinning. Again, they’ll start those controlled burns in the late winter or fall, to keep the fires from getting out of hand.

Such a policy could prove good for the planet, concluded Christine Wiedinmyer at the NCAR along with co-author Matthew Hurteau, with Northern Arizona University. The study was published in Environmental Science and Technology.

The researchers used satellite measurements and computer models to study the difference between a low-intensity controlled burn and an all-out wildfire.

First, they estimated the amount of carbon dioxide pumped into the atmosphere by fires in 11 western states between 2001 and 2008. Then they used a sophisticated computer model developed by Wiedinmyer to figure out how much carbon is released when a certain mass of vegetation burns.

Next, they estimated how much carbon would have gone up in smoke if those same areas had been treated with controlled burns.

They concluded that controlled burns of those areas would have reduced total carbon emissions by 11 million metric tons. That’s only a fraction of the total U.S. carbon emissions, but still exceeds the total produced by a host of smaller states.

New Mexico, Montana and Arizona would enjoy the biggest drop in potential emissions by using controlled burns to pre-empt wildfires — about a one-third reduction.

The researchers concluded that the controlled burns would also likely produce substantial health benefits, by reducing the amount of other pollutants released into the air — especially soot and other fine particulate matter. Several studies have demonstrated that such finely burned material can have a pronounced effect on the health of people with asthma and other breathing problems.

The study comes just as Rim Country forest managers are gearing up for the fall burn season — and for an innovative effort to use a retooled timber industry to thin some 700,000 acres of overgrown ponderosa pine forest in northern Arizona.

The 4-Forests initiative recently won a $2 million federal grant to prepare long-term contracts that would guarantee a steady wood supply for mills that could handle small-diameter trees.

Forest managers hope this approach will create more than 600 jobs in the region while eliminating the taxpayer cost of thinning huge expanses of forest.

The key to that effort lay in an agreement by loggers and forest managers to mostly not cut trees bigger than 16 inches in diameter.

As it happens, those are the trees capable of withstanding controlled burns and locking up huge amounts of carbon for centuries.

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