Since the start of the industrial revolution we have increased the atmospheric concentration of CO2 from 275 to 350 parts per million (ppm). This seemingly small increase corresponds to an atmospheric addition of approximately 650 billion tons. Americans are responsible for 26% of all CO2 being added to the atmosphere. Our wasteful use of fossil fuels combined with deforestation could well push the level to 550 ppm in another 60 years. Most scientists now agree that this trend will result in planetary warming, significant changes in weather patterns and rising sea levels. There is little doubt that the planet's ecological integrity is seriously threatened. These changes will have far reaching effects on plant communities and wildlife as well as man. We are in the midst of an experiment of global proportions with potentially disastrous results. The direct and indirect costs of such a disaster are almost beyond comprehension.
As you probably know, every cubic foot of wood contains the carbon equivalent of about 50 pounds of CO2. It has been estimated that if all of Earth's current biomass was consumed, the atmospheric concentration of CO2 would triple. Conversely, if the Earth's standing biomass was increased by only 33% the atmospheric concentration of CO2 would be returned to normal. The need for reforestation is obvious.
But what I particularly want to focus on goes beyond reforestation. It is the need for mature forests as well. At the risk of boring you, I'd like to cite some figures from the California Forestry Handbook. I will use site index 160 coast redwood as an example. The Forestry Handbook shows that an acre of 20 year old redwoods contains about 2300 cubic feet of wood, the equivalent of 57 tons of CO2. An acre of 40 year old trees contains the equivalent of 181 tons of CO2, while an acre of "mature" 120 year old trees (trees which have reached maximum mean annual growth) contain 712 tons per acre. According to Franklin, an old growth forest could contain the equivalent of 2000 tons per acre.
To put it in relative terms, an acre of 120 year old redwoods contains 12.5 times the CO2 content of 20 year old trees, 3.9 times the CO2 content of 40 year old trees, but only 35% of the CO2 content of an old growth stand. The biomass advantage of a mature or old growth stand is obvious.
I'm not sure what the current average age of our forests is, but discounting the small fragments of remaining old growth, my suspicion is somewhere around age forty. As more and more plantation type tree farms are established in the rush for short term profits, I suspect the average forest age will sink even lower. The implications for removal of CO2 from the atmosphere are obvious. Lowering the average age of the forests is simply another form of deforestation.
The California Forest Practices Act mandates the continued production of high quality timber products. The harvest of immature trees fails to fulfill this mandate. The quantity of lumber (board feet) produced by 3 harvests of 40 year old trees is about 60% that produced by a single harvest of 120 year old trees and the quality is notably inferior. The reduced volume of lumber results in fewer jobs. And as discussed above, the amount of CO2 stored in an immature stand is vastly reduced. All but the timber interests are poorly served by the rush to harvest immature trees.
I urge the Board of Forestry to consider regulations which will result in the sustained and respectful harvest of mature forests. We must take responsibility for our contribution to the impending greenhouse disaster. By doing so we will also set a beneficial example for others to follow.
Copyright Mendocino Environmental Center 2003
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