'Green' storage in forests may be going up in smoke

A new study has found that California wildfires emit more greenhouse gases than previously believed largely through the post-fire decay of dead wood, a finding that is raising questions about how effective the state's forests are at storing carbon and slowing global warming.

The study by Thomas Bonnicksen, a retired forestry professor at Texas A&M University, found that four major wildfires – from the Fountain fire near Redding in 1992 to the Angora blaze at Lake Tahoe last year – are responsible for the release of 38 million tons of greenhouse gases into the atmosphere, far more than the 2 million tons the state estimates that fires produce on average each year.

"Up until now, we have not fully appreciated the magnitude of the impact of wildfires on climate change," Bonnicksen said. "This is a very important part of the problem."

His study, which is not peer-reviewed and has been found lacking by some, is one of a flurry of reports that have begun to explore the critical role that forests play in regulating carbon dioxide, the principal atmospheric gas responsible for global warming. Traditionally, forests have been viewed as green reservoirs of landlocked carbon, soaking up and storing CO 2 from the atmosphere in their leaves, needles, roots and soil.

Bonnicksen's study casts that view into question. Forests today are so overcrowded with spindly, unhealthy trees – partly the result of decades of fire suppression – that as they burn and decay they are turning into an actual source of greenhouse gas pollution.

His study, for example, estimates emissions from just one blaze alone last year, the Moonlight fire in Plumas County, at more than 19.6 million tons, three-quarters of which are expected to occur over the next century as trees killed by the fire decay. That much carbon is roughly equivalent to the emissions from 3.6 million cars for a year.

Overall, California fires are producing so much CO 2, he said, that they will defeat the state's pioneering efforts to respond to climate change by reducing emissions elsewhere.

"No matter what anybody does in California to reduce greenhouse gas emissions, as long as these forests are burning, they are wasting their time," Bonnicksen said.

Officially, state officials still view California's forests as a carbon reservoir that stores 13 million tons of CO 2 a year and emits an average of only 2 million tons through wildfires. But Richard Bode, chief of the emissions inventory branch with the California Air Resources Board, said those numbers are based on old data and the agency is going to take another look.

Asked about Bonnicksen's report, Bode said: "It looks like his numbers are on the far end of the spectrum, the high end."

Mark Nechodom, climate science policy coordinator for the U.S. Forest Service who reviewed Bonnicksen's study, also said the numbers seem high.

"The structure of his analysis is correct," Nechodom said. "The areas of disagreement are about the data. … He may be overestimating."

But Nechodom also said that while Bonnicksen's work on decay isn't the very first study to look at the issue, it does contribute to further the examination of the important topic.

"One of the things we know very little about is the actual amount of decay coming out of forest ecosystems," he said.

Last fall, a separate study by the National Center for Atmospheric Research at the University of Colorado, Boulder, estimated that wildfires nationwide release about 290 million metric tons of carbon dioxide into the atmosphere – 4 percent to 6 percent of fossil fuel burning emissions.

The center also estimated that in one week alone, last year's Southern California wildfires emitted 7.9 million tons of CO 2.

Bonnicksen said that while his study emphasizes the role of decay in carbon emissions, there is a solution.

"Removing dead trees and storing the carbon they contain in solid wood products consumers need can reduce total CO 2 emissions by as much as 15 percent," Bonnicksen said in his report. "Planting a young forest to replace one killed by wildfire and letting the growing trees absorb CO 2 from the atmosphere through photosynthesis is another way."

But such suggestions stand to stir more conflict.

"Climate benefits are not the only issue," said Bill Stewart, a forest specialist with the University of California Cooperative Extension program. "We have endangered species out there, concerns over water quality and fish habitat that also have to be taken into account. It isn't just climate."

Bonnicksen's work has been challenged previously – with critics noting he often sides with the timber industry. His study was funded by the Forest Foundation, an Auburn nonprofit group that is supported by contributions from a mix of sources, including lumber companies.

Bonnicksen, though, dismissed such criticism.

"I'm a scientist. I really don't care what they say," he said. "What I care about is the underlying facts. I want society to make informed choices."

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