Northern Arizona University researchers have found that prescribed burning reduces the amount of carbon emitted to the atmosphere and increases the forest’s long-term ability to store carbon.
These burns consume less biomass, releasing less carbon than wildfires of the same size and create healthier forests better able to sequester carbon, the study indicates.
Researchers used satellite images and computer models to analyze 11 Western states from 2001-08. They found prescribed burns can reduce carbon emissions by an average of 18 percent to 25 percent and by as much as 60 percent in certain forest systems.
As the world searches for ways to reduce carbon emissions, from carbon capping and trading to legislation requiring renewable energy use, the ability of prescribed burning to both enhance carbon storage and reduce wildfire carbon emission is crucial, especially since wildfires are only increasing in size and severity, researchers say.
Aggressive fire suppression intended to store carbon in forests thick with small trees is like “placing your whole retirement fund in high-risk stocks—the yield is high, but so is the risk,” said NAU research associate Matthew Hurteau, the study’s co-author. Storing carbon in larger trees and making forests more resistant to severe wildfires is like “investing in bonds, where the yield is lower but more secure.”
Low-intensity, prescribed burns do three beneficial things to secure carbon storage: burn less biomass than wildfires and consequently emit less carbon, reduce the risk of high intensity wildfires by removing fuel, and kill fewer large trees, leaving the forest more intact with living tress that store carbon in their biomass.
“By applying prescribed fire to manage surface fuels, when subsequent fires occur they will be less intense and tree mortality rates will be lower than under high severity wildfire conditions,” Hurteau said. “With more living trees, the forest will sequester more carbon.”
Dry forests in the West historically burned frequently, but years of fire suppression and an increasing fire season length have resulted in the occurrence of larger, more severe wildfires.
A 2008 U.S. Energy Information Administration report predicts that wildfires will consume 10 million to 12 million acres each year. Only 9.9 million acres burned in 2007, the worst of the last five years.
The forests in northern Arizona will be no exception to this increase in wildfire. Currently, land management agencies and city/county fire departments regularly conduct prescribed burns to reduce fire hazard.
“Dry forests, such as southwestern ponderosa pine, are going to burn eventually,” Hurteau said in regard to this year’s upcoming fire season. “If forest managers conduct regular prescribed burns, the overall effect from an ecological perspective is a better functioning forest. From a human perspective, the overall effect is a safer forest.”