Northwest forests offer carbon dilemma

WASHINGTON – A new study using laser pulses shot from satellites has found that the world’s tallest forests are those along the Pacific Northwest coast.

Though the findings shouldn’t shock anyone who grew up in the region, they offer another indication of how important these ancient trees eventually could become.

The temperate forests of Douglas fir, Western hemlock, redwood and sequoia that stretch from Northern California into British Columbia easily reach an average height of more than 131 feet.

That’s taller than the boreal forests of Northern Canada and Eurasia, tropical rainforests and the broadleaf forests common in much of the U.S. and Europe.

The only forests that come close are in Southeast Asia, along the southern rim of the Himalayas and in Indonesia, Malaysia and Laos.

As scientists try to unravel the mystery of missing carbon, increasing attention is focused on these forests.

From 15 percent to 30 percent of the 7 billion tons of carbon that are released globally every year is unaccounted for, government scientists say. About 3 billions tons remain in the atmosphere, and the oceans absorb 2 billion tons. Vegetation, including the forests, probably absorbs the remaining 1 billion to 2 billion tons, but no one knows for sure how much and where.

Scientists suspect that the forests with the biggest trees store the most carbon, and the Northwest forests are probably among the largest carbon sinks in the world. However, they also say that while slower-growing older trees store more carbon, younger trees absorb more carbon as they grow rapidly.

That sets up a debate about how forests should be managed, particularly whether older trees should be cut to make way for younger ones or whether they should be protected to store carbon they contain.

“It’s a hot topic,” said Elaine Oneil, a research scientist at the University of Washington’s School of Forest Resources and the executive director of a consortium that’s been studying the issue. “We can’t afford a one-size-fits-all solution. We can’t lock it all up, and it’s not feasible to cut it all for two-by-fours.”

Studies using the satellites and lasers may provide valuable information on how fast the forests are growing and how much carbon they store.

“All of the remote sensing is providing us with the ability to monitor changes in the environment in a way you might not see on the ground,” said Michael Lefsky, an assistant professor in the department of forest, rangeland and watershed stewardship at Colorado State University. “We are expecting under global warming that the productivity of the forests will change.”

Lefsky used data from a laser technology called LIDAR that’s capable of “capturing vertical slices” of surface features on Earth from satellites. It’s the same technology used to map earthquake faults in Western Washington.

Lefsky said he wasn’t surprised that the temperate conifer forests of the Northwest coast had the tallest canopies. While the Northwest forests include the world’s tallest trees – redwoods and sequoias – they represent only a small fraction of the region’s timberlands, he said, but there are thousands of acres of other tall trees.

Trees absorb carbon dioxide, a greenhouse gas, and convert it using water into sugar and oxygen. Much of the sugar becomes cellulose, the key ingredient in wood. From 45 percent to 50 percent of a tree’s wood is carbon-based.

The trees and soil in national forests in Washington state, Oregon and southeast Alaska store 10.8 billion tons of carbon, according to a Wilderness Society analysis of U.S. Forest Service data earlier this year.

The analysis also found that of the 120 national forests, the 10 with the highest carbon density were in Washington, Oregon and southeast Alaska.