Impacts of California Wildfires on Climate and Forests: A Study of Seven Years of Wildfires (2001-2007)
Thomas M. Bonnicksen. 2009. Impacts of California Wildfires on Climate and Forests: A Study of Seven Years of Wildfires (2001-2007). FCEM Report No. 3. The Forest Foundation, Auburn, CA.
Full text [here]
See also FCEM Reports No. 1 and 2 [here]
Selected Excerpts:
Executive Summary
This study (FCEM Report No. 3) and the previous study (FCEM Report No. 2), use a new computer model, the Forest Carbon and Emissions Model (FCEM), to estimate greenhouse gas emissions from wildfires and insect infestations, and opportunities to recover these emissions and prevent future losses.
This report shows that the wildfires that scorched California from 2001 to 2007 seriously degraded the state’s forests and contributed to global warming. Political and economic obstacles to managing forests and restoring burned forests are the root causes of the wildfire crisis.
The impact of California’s wildfires on climate and forests is one of the most important issues of our time. It is imperative to take action now to prevent the annual recurrence of disastrous and costly fire seasons.
The wildfire crisis is becoming more serious each year. Fires are getting bigger, more destructive, and more expensive. In 2001, California wildfires burned one-half million acres. In 2007, 1.1 million acres burned, and an estimated 1.4 million acres burned in 2008 destroying 1,000 homes. This was the most destructive fire season in the state’s history and 2009 could be worse.
From 2001 to 2007, fires burned more than 4 million acres and released an estimated 277 million tons of greenhouse gases into the atmosphere from combustion and the post-fire decay of dead trees. That is an average of 68 tons per acre. These wildfires also kill wildlife, pollute the air and water, and strip soil from hillsides. The greenhouse gases they emit are wiping out much of what is being achieved to reduce emissions from fossil fuels to battle global warming.
The emissions from only the seven years of wildfires documented in this study are equivalent to adding an estimated 50 million more cars onto California’s highways for one year, each spewing tons of greenhouse gases. Stated another way, this means all 14 million cars in California would have to be locked in a garage for three and one-half years to make up for the global warming impact of these wildfires.
The catastrophic and unnatural forest fires that ravage California each year do not resemble historic fires. 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.
Even chaparral fires in the vast brushlands of Southern California were limited in extent in past centuries. Frequent fires sustained a mosaic in which old flammable chaparral was isolated between patches of less flammable young chaparral, which kept wildfires from spreading across the landscape, regardless of strong winds. Today, old chaparral stretches across huge areas to fuel massive fires that destroy human lives and homes.
It is not realistic or acceptable for an industrialized, modern society to live with the annual recurrence of unnatural catastrophic wildfires. To protect our communities, forests, and climate, we must reduce the threat of wildfires. That means not just fighting fires, but taking action to reduce fuels to prevent them.
Although hundreds of millions of dollars are spent fighting wildfires each year, very little is spent on fuel reduction. Since forests keep growing thicker and surface fuel continues to pile up, wildfires are getting bigger and more destructive.
Some public forests in California have more than 1,000 trees per acre when 40 to 60 trees per acre would be natural. These dense forests contain small trees that can carry fire into the canopy, and heavy concentrations of woody debris lying on the ground intensify the flames. This combination of too many large trees intermixed with small trees and surface debris are responsible for the size and severity of many forest fires.
Reducing the number of all sizes of trees per acre by thinning is effective in helping prevent crown fires in forests. This was demonstrated in two California wildfires – the Cone Fire in 2002 and the Bell Fire in 2005. These crown fires dropped to the ground and became light and easily suppressed surface fires after entering thinned forests. We should use this knowledge and act quickly to prevent catastrophic wildfires before they destroy more property, lives, and forests, and further alter the global climate.
This is only part of the wildfire tragedy. During the seven years covered by this study, California wildfires deforested about 882,759 acres of public and private land and only an estimated 120,755 acres were replanted. That means about 762,004 acres of forest converted permanently to brush because no live trees remain standing to provide seed for a new forest. That is an average loss of about 109,000 acres of forest each year, or the equivalent of an area nearly four times the size of San Francisco.
Not only are wildfires causing California’s forests to dwindle, but the greenhouse gases they emit will stay in the atmosphere for centuries. The estimated 134 million tons of carbon dioxide (CO2) released by fires and the decay of dead trees from forests that were permanently converted to brush from 2001 to 2007 will continue to worsen global warming.
Harvesting dead trees to prevent them from releasing CO2 from decay, storing the carbon they contain in long-lasting wood products, and using the money to replant a young forest that absorbs CO2 through photosynthesis is the only way to restore deforested areas and recover this greenhouse gas from the atmosphere.
The immensity of greenhouse gas emissions from California’s wildfires and the permanent loss of huge areas of forest are a warning. Clearly, we must make every effort to reduce the amount of fuel in public and private forests to prevent catastrophic wildfires. That means decreasing the number of trees of all sizes by thinning to make forests resistant to crown fires. We must also harvest fire-killed trees and replant young trees in burned forests to replace what was lost.
If we take these steps, we will restore the natural health and diversity of our forests, help the fight to reduce harmful emissions, and leave a legacy of which we can be proud.
