Study says carbon absorption slows as trees age

By STEVE BROWN

Capital Press

A report that found logging mature trees and replacing them with young, fast-growing trees as a way to increase carbon sequestration may ultimately be a boon to the region's timber industry, officials said.

The Consortium for Research on Renewable Industrial Materials found that carbon absorption by trees slows when they reach 30 to 70 years of age. Elaine Oneil, executive director of the group, also said younger trees absorb more carbon as they grow.

Carbon dioxide is a "greenhouse" gas, which many scientists believe contributes to global warming. By absorbing more carbon dioxide, the younger trees would help reduce global warming.

Rather than leaving all of a forest's tall trees in place, Oneil said, the older ones could be cut and used for building material. The carbon in that wood would be stored permanently.

Also, the leftovers from milling the logs could be used for mulch and biofuel, she said.

"It validates what we believe, that sustainably managed forests play an important part in the climate-change discussion," Anthony Chavez, public affairs manager for timber company Weyerhaeuser, said.

"This could create more demand," Chavez said. "With the right 'green' building policies in place, we could change the building materials being used. This is an opportunity for forest products as a tradable commodity in green building."

Satellite-based laser measurements found that the average height of temperate forests along the West Coast is more than 130 feet, taller than boreal forests in Eurasia and Canada, tropical rainforests and broadleaf forests in Europe and the U.S. The only comparable forests are in Southeast Asia.

Scientists studying the absorption of carbon dioxide from the atmosphere suspect that forests with the biggest trees store the most carbon, which would mean the coastal forests from California through British Columbia are among the largest carbon "sinks" in the world.

Oneil, also a research associate at the University of Washington's School of Forest Resources, said the consortium does not recommend cutting all old-growth forests, which are critical for wildlife habitat and recreation. But she did suggest forests could be managed to absorb more carbon.

"If you don't pick the carrots, you can't plant the next crop," she said.

Rick Dunning, executive director of Washington Farm Forestry Association, said, "This study is going to help recognize the great value of all forestry. You don't want to point a finger at old growth vs. new growth."

Dunning represents small forest land owners, who have few old trees, he said. "The study is not really a hope for tree farmers, but it extends the dialogue of current policy, which is eroding rather than promoting forestry."