The Hidden Cost of Using Wood as Biofuel


A forest after clearcutting. (Photo by Dave Powell, USDA Forest Service, via Forestry Images)


Coal stacks spewing thick black smog may be the emblem of pollution, but an overlooked source of carbon emissions is pouring from the soil when forests are chopped for timber, according to a new report by Dartmouth University researchers.

Forest soils contain an enormous amount of carbon—2,500 gigatons, or about 2.5 million times the amount of carbon each year emitted by American cars and trucks. More than half of that carbon is buried deeper than three feet underground. But because this carbon was thought to be unaffected by logging, it is rarely included in estimates of the impact forestry projects have on carbon emissions.

The researchers rounded up data from recent studies to take another look at how deforestation techniques affect deep soil carbon. They found that the amount of carbon released depends on how heavily an area is logged and on the type of soil. Clearcutting, for instance, disturbs more deep soil carbon than does smaller scale timbering. While more research is needed, the researchers say these data should inform policy regarding forest management. Logging can be done sustainably, but the hidden cost of deep soil carbon emissions is another part of the equation. 


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