Scientists look to redwoods for answers on warming

Ukiah, Mendocino County — Stephen Sillett swung from a rope in the second-tallest redwood tree in Montgomery Woods State Natural Reserve in Mendocino County and shouted measurements to his colleagues on the ground.

The professor of forest ecology at Humboldt State University has been clambering around a lot lately on the 365-foot-tall giant, which is believed to be well over 1,000 years old. He can tell you the number of branches, 403, and estimate the number of leaves, 514 million.

But the thing Sillett really wants to know is this: How will global warming affect this majestic tree and the other ancient redwoods in California?

The tree, an ecosystem in itself, is a treasure trove of information that Sillett and other leading scientists believe will lead them to the answer.

"Locked in the rings of these trees is a history of everything they have been through," said Ruskin Hartley, executive director of Save the Redwoods League, a San Francisco advocacy group that gathered a crack team of scientists and embarked this year on the most intensive research project ever conducted on the giant trees.

By studying the rings, scientists hope to be able to forecast how the redwoods will change as the Earth warms up. One thing they've already learned is that these trees play a huge role in removing from the atmosphere the carbon dioxide that traps heat on Earth and leads to global warming.

Size and growth

"What we're seeing is that the bigger the tree is, the more it grows," said Sillett, a pioneer in research high in the redwood forest canopy. "The bigger and older the tree, the more wood production there is. So pound for pound, you are going to get more carbon sequestered."

The $2.5 million Redwoods and Climate Change Initiative has allowed Sillett and other specialists from Humboldt State and UC Berkeley to set up shop in some of California's last remaining old-growth redwood groves. The researchers are climbing, poking, prodding, measuring and testing everything, including molecules of coast redwood and giant sequoia trees on 16 research plots throughout the ancient trees' geographic range.

The plan is to chart the health of the trees over time and use laboratory analysis of carbon and oxygen isotopes to figure out how the trees have reacted in the past to climate and weather conditions.