Wildfire warming effects

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California has gained an international reputation for its efforts to fight global warming — but the progress the state makes is often undone right here at home.

The catastrophic and unnatural forest fires that ravage California each year don't resemble the historic fires that took place in these forests for millennia. Frequent lightning and Indian-set fires that burned along the ground, igniting only scattered small groups of trees, kept forests open and healthy, and resistant to catastrophic fires.

Some people argue we have to live with fire. On the contrary, an industrialized world can't live with fire. We would have to move out of our forests to be safe and get out of our cars to eliminate tailpipe emissions to make up for the greenhouse gases that wildfires emit into the atmosphere.

That isn't realistic, so the only solution is to fight global warming and protect our communities and forests by reducing the threat of catastrophic wildfires.

In an extensive study I authored for the Forest Foundation, the findings show four notable California fires — Angora, Fountain, Star and Moonlight — have or will spew an estimated 38 million tons of greenhouse gases into the air, equivalent of adding 7 million cars to our roads for a year.

The study utilizes a new computer model developed specifically to quantify the impact of fires and insect infestations on global warming.

Why do many forests burn? They have too many trees.

The four fires analyzed averaged 350 trees per acre where 50 trees per acre would be natural. Some California forests have over 1,000 trees per acre. These dense forests, especially with small trees growing under larger trees as ladder fuel, and woody debris on the ground, are the two most important contributors to the size and severity of wildfires.

Consequently, when the massive amounts of fuel in these four forests burned, they released an estimated 9.5 million tons of greenhouse gases into the atmosphere just from combustion. That is an average of about 63 tons per acre.

However, combustion is only part of the story because dead trees also release carbon dioxide as they decay. Emissions from decay are generally 3 times greater than from combustion because large quantities of dead wood remain after a fire.

Combining combustion and decay emissions, the study found these four fires will emit a staggering 38 million tons of greenhouse gases into the atmosphere. The fires released 25 percent of the gases during combustion and post-fire decay will release most of the remainder during the next 50 years.

Obviously, something must be done. The most important question is: Can we recover from our mistake of letting forests become unnaturally overcrowded with trees and vulnerable to catastrophic wildfires? The answer is "yes," if we care about restoring our forests and fighting global warming.

The immensity of greenhouse gas emissions from just these four wildfires is a warning. Clearly, we must make every effort to reduce the excess biomass in forests to help prevent catastrophic wildfires. That means decreasing the number of trees by thinning, which will restore the natural health and diversity of our forests and make them more resistant to crown fires. Harvested trees can be turned into long-lasting wood products that store carbon.

If a fire occurs, it is critical to remove the dead trees so they don't decay and send more carbon dioxide into the atmosphere. This also would store carbon in wood products that people need and provide money to replant a new forest that will reabsorb the carbon dioxide lost in the wildfire.

While California's actions to reduce global warming are significant, reducing the number and severity of wildfires may be the single most important short-term action we can take to lower greenhouse gas emissions and really fight global warming.

Thomas M. Bonnicksen is professor emeritus of forest science at Texas A&M University, research scholar in residence at California Polytechnic State University, San Luis Obispo, visiting scholar at the Forest Foundation and author of the study, "Greenhouse Gas Emissions from Four California Wildfires: Opportunities to Prevent and Reverse Environmental and Climate Impacts," which can found at www.calforestfoundation.org.