Controlled fires are often used by forest rangers to reduce the chances of dangerous wildfires. However, new research shows that these prescribed burns can also serve an environmental benefit. According to a study by the National Center for Atmospheric Research, an expansive system of controlled burns produces significantly less carbon dioxide emissions than wildfires of equal size. Using satellite observations and computer modeling, the scientists discovered that widespread prescribed burns can reduce fire emissions of carbon dioxide in the Western U.S. by an average of 18 to 25 percent and by as much as 60 percent in particular forest ecosystems.

The scientists used a model that estimated carbon dioxide emissions from wildfires in 11 Western states from 2001 to 2008 based on the mass of vegetation burned. They compared that to the amount of emissions that would have been released if those forests had been exposed to comprehensive controlled burns. The results showed that carbon emissions for the specific states were reduced by an annual average of 14 million metric tons.

Uncontainable wildfires often destroy bigger trees that serve as repositories for large amounts of carbon, while controlled burns target underbrush and small trees, which store significantly less carbon. By eliminating fire-prone underbrush, the controlled burns keep the larger trees’ carbon secured in the forest and out of the atmosphere. Prescribed fires can help offset the significant amount of carbon dioxide released by other sources such as factories and motor vehicles. “While it can be costly to set controlled fires, there is also a cost in leaving forests vulnerable to larger fires,” Christine Wiedinmyer, the lead author of the study, said.

http://www2.ucar.edu/news/prescribed-burns-may-help-reduce-us-carbon-footprint