Forest Thinning Would Cut Release Of Greenhouse Gas


Turning overgrown Arizona forests into wood products and fuel for power plants could significantly reduce emissions of planet-warming greenhouse gases, conclude Northern Arizona University researchers.

If the United States ever does buy into a global effort to reduce such carbon emissions by creating a market for “carbon credits,” the extra cash could make efforts to thin millions of acres to protect forest communities cost effective, according to Ecological Research Institute (ERI) researchers Dave Egan and Joseph Seidenberg in a recently published White Paper.

Converting dense, overgrown forests into less dense forests with more meadows and grasslands will reduce the amount of carbon put into the air during catastrophic wildfires — while storing millions of tons of carbon in the soil.

Moreover, converting spindly trees waiting for that next big fire into wood pallets, two-by-fours, other wood products or fuel for a regional network of small biofuel power plants would potentially store excess carbon for long periods.

The advantages of biofuel power plants seemed especially pronounced in the study. Such small, local, wood-burning power plants with modern pollution controls would release 86 percent less carbon into the atmosphere than producing the same amount of energy from gasoline, the study concluded. Such power plants would cost about the same as coal, but release fewer greenhouse gases.

Moreover, building such small power plants would provide a huge economic boost to timber companies doing the thinning, by providing a market for material they would otherwise have to burn off or discard.

“Adding biomass sales to existing high-value timber sales may be one of the best ways for timber concerns to survive and grow new markets,” the study concluded.

Researchers based many of their projections on a small, intensively-studied thinning project on an experimental plot near Flagstaff. In that study, crews reduced the number of small ponderosa pines from 231 trees per acre to 65 trees per acre.

The project reduced the total amount of biomass from 93,000 pounds per hectare (about 2.5 acres) to about 30,000 pounds per hectare.

The project actually resulted in the short-term release of extra carbon dioxide into the atmosphere, since the crews burned off the big slash piles.

However, the project would have actually stored 7,387 pounds of carbon per hectare if the wood had been converted into pallets. The project also prevented the future release of 5,300 pounds of carbon per hectare if the future big reduction in fire risk is included.

The researchers concluded that the free market could create the money needed to thin huge expanses of overgrown forest in the Southwest if now-faltering efforts to create a global market in “carbon credits” ever takes off.

President Obama and Congressional Democrats had proposed a “cap and trade” marketplace for carbon credits, building on greenhouse gas control efforts in Europe. So far, Senate Republicans have blocked the legislation on the grounds it could hurt industry and drive up consumer prices. The cap and trade system would allow companies producing greenhouse gases like power plants and factories to buy carbon credits from projects that reduce carbon releases — like restoration forest projects in the Southwest.

The NAU researchers noted that current consensus projections envision a 3.3- to 7.2-degree F rise in global temperatures by 2100. Such a “rapid and profound” rise would have serious global consequences and would result in more weather extremes, extended droughts and ecological changes in the Southwest.

Such a projected warming could cause a pronounced shift in ecosystems. For instance, Payson now sits at the southern, lower-elevation edge of the world’s largest ponderosa pine forest, which could shift to higher elevations as temperatures rise, the researchers concluded.

The shifts could cause more frequent and longer-lasting droughts, like the past decade in Rim Country that has been associated with massive wildfires and mass tree die-offs from things like bark beetles.

Worldwide, soils and vegetation store about 2,000 billion tons of carbon, according to the study.

In the U.S., about a third of the land surface is forested. The soils and plants in those forests remove about 200 million metric tons of carbon from the air each year — far less than the 1,600 million tons released into the atmosphere — mostly through human activities, the researchers say.

Plants remove carbon dioxide from the air, which they use to fuel photosynthesis — releasing oxygen in the process. Growing trees absorb carbon dioxide, while dead, decaying trees release it. A ponderosa pine peaks in its absorption of carbon dioxide at about 70 years of age, when a mature tree will soak up three tons of carbon annually.

Wildfires release huge amounts of carbon dioxide all at once. Such carbon gases let most of the sun’s energy through the atmosphere, but absorb and so block the infra-red frequencies of radiation produced by the heated surface of the Earth.

Wildfires account for about 5 percent of the carbon released into the atmosphere annually nationwide — and a much higher share in the west, the report states.

However, figuring out how much carbon credit to give restored forests or reduced wildfires has proven complicated. Certainly, trees absorb and store carbon as they grow — but then they release much of that carbon when they either decay or burn.

If loggers turn a tree into pallets, the carbon still ends up in the atmosphere if someone throws the pallet on a bonfire after a couple of years. Likewise, two-by-fours used in a house store the tree’s carbon for an extra century, on average, but release the carbon if that house is demolished and burned up.

Still, estimates suggest that the timber industry overall removes more carbon than it releases, the report concluded.


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