Old-growth forests store a treasure trove of carbon
BILL KEETON
growth forests globally have watershed protection, the best As climate change legislation carbon storage value. thing is to avoid deforestation, plows its way through the U.S. By comparison, when a forest is says Law. Congress, one of the hot-button cut, the regenerating young forest But people still need wood, says issues is how to award greenis an annual source of carbon, Jared Nunery, a forest ecologist at house gas offset credits for storaccording to research by Bev Law, the University of Vermont. So he ing carbon in forests. Some an ecosystem scientist at Oregon and Keeton have been testing the timber industry advocates argue State University, because CO2 reeffect of different silvicultural that cutting trees can lead to methods on carbon more sequestration of carsequestration. bon than leaving forests Even when taking carbon unmanaged. But a growing storage in durable wood body of research shows products into account, intact that old-growth forests are northeastern forests store best left alone, since they more carbon than harvested store two to three times the ones, Nunery says. Comcarbon of typical managed pared to an untouched forforests. est, clear-cutting retains only Because trees absorb and 45% of the original carbon store CO2 from the atmoreservoir, and harvesting sesphere as they grow, the Inlected trees retains 79% of tergovernmental Panel on the carbon. But managing Climate Change recognizes for old-growth characterisreforestation, afforestation This 300-year-old forest in the Adirondack Mountains of tics by less frequent cutting, (converting fields into forNew York hoards vast amounts of carbon in abovewhich maintains a multilayests), and avoiding defores- ground live wood, roots, dead wood, and soil. er forest canopy and leaves tation as ways to mitigate lots of dead tree trunks and limbs climate change. However, some lease from soil and decomposion the forest floor, preserves 90% industry advocates say that betion outweighs the carbon taken of the carbon sequestration. cause young forests sequester carup by young trees for an average Because such old-growth silvibon at a faster rate than old of 15 years. “When you harvest an culture boosts carbon stores comforests, offset credits should be old forest, you create a source of pared to “business-as-usual” awarded for replacing old slowcarbon immediately,” says Law, cutting methods, it has the “addigrowing forests with young inten“and the total amount of carbon tionality” needed to qualify for sively managed plantations. that was removed won’t be reoffset credits, Keeton says. This “The old view is that once a placed by regrowing forest for holds true as long as reduced harforest passes its peak rate of over 100 years.” vest does not lead to substitution growth, everything starts dying When a forest is logged, a great of energy-intensive products such and carbon just fluxes back into deal of carbon can be lost beas concrete and steel, or inthe atmosphere,” says Bill Keeton, cause of accelerated decomposicreased logging abroad. a forest ecologist at the University tion of woody debris and losses The next step is totaling up of Vermont. But nothing could be during manufacturing, adds Mark the value in carbon credits of further from the truth, he notes. Harmon, a forest ecologist at Orold-growth silviculture. “CaliforData from temperate forests egon State University. “Thus, it nia is the first governmental around the globe reveal that not may be eventually possible to body in the world to provide a only do old-growth forests congain carbon by converting an system for quantifying emissions tinue to sequester carbon for cenolder forest to a younger biomass reductions that are created turies, they also store 30-50% energy plantation, but it may take through changes in forest manmore carbon than middle-aged many decades or even centuries agement,“ says Laurie Wayburn, forests and much more than for this to occur. This is time we president of Pacific Forest Trust, young forests, Keeton reported at do not have,” he said in testia conservation organization. the Ecological Society of America mony before Congress on March ”Landowners must conduct a annual meeting on August 5. 3. full life-cycle assessment in orHis findings join a host of paWhen managing forests for carder to qualify for an emission pers published over the past sevbon storage and other ecosystem reduction project,” she says. eral years demonstrating that oldservices, such as biodiversity and 7602 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / October 15, 2009
10.1021/es902647k
2009 American Chemical Society
Published on Web 09/09/2009
Wayburn’s group is managing the van Eck Forest Project in Humboldt County, the first forest carbon project registered with the California Climate Action Registry. To achieve CO2 emissions reductions, the forest’s redwood trees will be allowed to grow older and therefore larger than under a
business-as-usual forestry scenario. The amount of timber harvested from the property will always be less than the volume of new forest growth. The changes will allow the land to sequester an additional 500,000 metric tons of CO2 over the next 100 years.
“But keep in mind that the most important thing is to take quick action to stop pumping greenhouse gases into the atmosphere,” Law warns. —JANET PELLEY
October 15, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 7603
