211 / 33 37Logging may ditrupt balance in old forests

WASHINGTON (AP) — Harvesting ancientforests in the American Northwest contributesto the global greenhouse effect by releasingmillions of tons of carbon dioxide into the at-mosphere, even when the old trees are re-placed by new seedlings, researchers report. .

Mark Harmon, a researcher at the Depart-ment of Forest Service at Oregon State Uni-versity, said Thursday the "conventional wis-dom" is that harvesting old trees and thenplanting vigorous young seedlings will havethe net effect of reducing atmospheric carbondioxide, one of the major greenhouse gases.

"When you look at the large amount of car-bon stored in these old-growth forests, youcan see that is not true," said Harmon. Evenwhen new trees are planted, he said, "theyoung forest simply doesn't store anywherenear as much carbon as the old forest."

Harmon said more than half of the woodcut from old forests is burned or used in otherways that give off carbon dioxide into the at-mosphere. The harvesting iso disrupts a bal-ance that exists in old forests. Large trees ab-sorb carbon dioxide at about the same ratethat decaying, dead tree parts on the forest

"... we've been concernedthat decision makers aregoing to make important poli-cy decisions based on inaccu-rate, armchair ecology."

— Mark Harmon, researcher at OSU

floor give it off.He said he and his co-investigators studied

the effects of old forest harvesting on thegreenhouse effect because "we've been con-cerned that decision makers are going tomake important policy decisions based on in-accurate, armchair ecology."

Carbon dioxide and some other gases inthe atmosphere act as a blanket to trap heatgiven off by the Earth. This is called thegreenhouse effect. Some experts believe thata surplus of carbon dioxide is causing theEarth to slowly overheat, and they warn thatsuch a change could disrupt the global cli-

mate. Many scientists, however, disagree thatthe planet is warming up.

In a study to be published today in thejournal Science, Harmon reports that old-growth forests — areas that have never beenlogged — capture and store much largeramounts of carbon from the atmosphere thanyounger forests.

He said many believe that the old trees ag-gravate the greenhouse effect because old for-ests are littered with dead branches, leavesand other material that decays and puts car-bon dioxide into the atmosphere.

But Harmon said a computer study showsthat an old forest, with very large trees, actu-ally reaches a "carbon equilibrium" that nei-ther adds nor subtracts from the total carbondioxide in the atmosphere.

When the old trees are cut down, however,the forest litter continues to decay, giving offcarbon. And Harmon said it takes new seed-lings about 250 years to grow enough to rees-tablish the "carbon equilibrium."

Additionally, he said that only about 45percent of the wood harvested from old for-

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• Forests: harvestingContinued from front pageests is turned into lumber orother building materials that"store" carbon for long periods.Much of the material is burned,rots or is used for paper, allreleasing carbon into the atmos-phere over a short period of time.

In the past century, Harmonsaid, about 18 billion metric tonsof carbon have been released intothe atmosphere from harvestingof about 17.5 million acres of oldgrowth in western Oregon andWashington.

Land use changes, such as rip-ping out old forests, contributeonly a fraction of the carbon diox-ide that comes from the burningof fossil fuels, the scientist said.But Harmon said that on a globalbasis, the loss of forest land canbe significant.

Old forests in the Northwestare so productive and large, hesaid, that felling trees there canhave a greater impact per acre

than clearing of the tropical for-ests.

Harmon estimated that of thetotal carbon added to the atmos-phere in the past century by landuse change, 2 percent came fromharvesting forests in Oregon andWashngton, even though the areacovers only .017 percent of theEarth's land surface.

"We have very poor records ofland use change and how muchcarbon was in a forest before itwas lost," said Harmon. "As a re-sult, these estimates have notbeen as precise as fossil fuel. So Iwouldn't be surprised if the actu-al value is substantially largerthan we estimated."

The forest study was coau-thored by Harmon and William K.Ferrell of Oregon State Univer-sity, and Jerry F. Franklin of theUniversity of Washington. It waspublished today in Science, thejournal of the American Associa-tion for the Advancement ofScience.