Carbon sequestration a surprise benefit of forest plan

After the U.S. Northwest Forest Plan stopped most tree cutting on public lands, the area became a carbon sink for the first time in decades.

The U.S. Northwest Forest Plan, enacted in 1993, was designed to conserve old-growth forests and protect species such as the northern spotted owl, but researchers conclude in a new study published online July 14, 2011 in Forest Ecology and Management that it had another powerful and unintended consequence – increased carbon sequestration on public lands.

Many public lands in these areas affected by the Northwest Forest Plan are now sequestering more carbon. Image Credit: OSU

When forest harvest levels fell 82 percent on public forest lands in the years after passage of this act, the forests became a significant “carbon sink” for the first time in decades, absorbing much more carbon from the atmosphere than they released. At the same time, private forest lands became close to carbon neutral.

Researchers at Oregon State University and the Pacific Northwest Research Station of the USDA Forest Service created these assessments with a new system that not only incorporates satellite remote sensing, but also more accurately simulates ecological processes over broad areas. It considers such factors as the growth of trees, decomposition, fire emissions, climate variation and wood harvest.

Oregon coastal forest – prime habitat for the northern spotted owl. Image Credit: David Patte/US Fish and Wildlife

David Turner, a professor in the OSU Department of Forest Ecosystems and Society, said:

The original goals of the Northwest Forest Plan had nothing to do with the issue of carbon emissions, but now carbon sequestration is seen as an important ecosystem service. Forests provide many services, such as habitat protection, recreation, water purification, and wood production. Carbon sequestration has now been added to that list.

Coastal redwoods in northern California. Image Credit: TFCforever

Previous estimates of forest carbon balance had suggested a significant loss of carbon from Pacific Northwest forest lands between 1953 and 1987 associated with a high rate of old-growth timber harvest. Those harvests peaked in the mid-to-late 1980s.

Forest fire is also an issue in carbon emissions, but the researchers concluded that the magnitude of emissions linked to fire was modest, compared to the impacts of logging. Even the massive Biscuit Fire in southern Oregon in 2002 released less carbon into the atmosphere than logging-related emissions that year, they said.

The study analyzed an area that included western Oregon, western Washington and northern California.

In earlier work, Turner and other researchers found that carbon sequestration in Oregon – much of it from forests – amounted to almost half of the state-level carbon emissions from fossil fuel combustion. Nationally, forest carbon accumulation offsets about 15 percent of U.S. fossil fuel emissions.

Logging in national forests containing the northern spotted owl was stopped by court order in 1991. Image Credit: U.S. Fish and Wildlife Service

Bottom line: A study of forests in western Oregon, western Washington and northern California concluded that the 1993 U.S. Northwest Forest Plan had the unintended benefit of increasing carbon sequestration on public lands. Results of the study, led by David Turner, OSU, are published online in the July 14, 2011 issue of Forest Ecology and Management.

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