CORVALLIS, Ore. Contrary to 40 years of conventional wisdom, a new analysis to be published Friday in the journal Nature suggests that old growth forests are usually "carbon sinks" - they continue to absorb carbon dioxide from the atmosphere and mitigate climate change for centuries.
However, these old growth forests around the world are not protected by international treaties and have been considered of no significance in the national "carbon budgets" as outlined in the Kyoto Protocol. That perspective was largely based on findings of a single study from the late 1960s which had become accepted theory, and scientists now say it needs to be changed.
"Carbon accounting rules for forests should give credit for leaving old growth forest intact," researchers from Oregon State University and several other institutions concluded in their report. "Much of this carbon, even soil carbon, will move back to the atmosphere if these forests are disturbed."
The analysis of 519 different plot studies found that about 15 percent of the forest land in the Northern Hemisphere is unmanaged primary forests with large amounts of old growth, and that rather than being irrelevant to the Earth's carbon budget, they may account for as much as 10 percent of the global net uptake of carbon dioxide.
In forests anywhere between 15 and 800 years of age, the study said, the net carbon balance of the forest and soils is usually positive meaning they absorb more carbon dioxide than they release.
"If you are concerned about offsetting greenhouse gas emissions and look at old forests from nothing more than a carbon perspective, the best thing to do is leave them alone," said Beverly Law, professor of forest science at OSU and director of the AmeriFlux network, a group of 90 research sites in North and Central America that helps to monitor the current global "budget" of carbon dioxide.
Forests use carbon dioxide as building blocks
|Contact: Beverly Law|
Oregon State University