Fifteen centuries old and taller than a football field turned vertical, redwood trees stand mute along the South Fork of the Eel River in Humboldt County.
But the old-growth forest titans are slowly surrendering their secrets to a team of scientists and conservationists armed with high-tech gadgets and daring tree-scaling skills who have mastered ways to penetrate the redwoods to their core.
The redwoods "hold a record of everything they have experienced in their lifetime," said Ruskin Hartley, executive director of Save the Redwoods League.
Hartley spoke Tuesday at the edge of Rockefeller Forest, a 10,000-acre portion of Humboldt Redwoods State Park about 40 miles south of Eureka that is the largest forest of old-growth redwoods on the planet.
He was introducing the Redwoods and Climate Change Initiative, a three-year, $2.5 million project aimed at assessing how coast redwoods, the world's tallest trees, and the inland Giant sequoia, the most massive tree species, are likely to fare against rising global temperatures.
The ancient giants are likely to survive, but the species faces an uncertain future amid what Hartley called a "maelstrom of changes," including climate, urbanization, pollution, pathogens and invasive species.
"We are facing an unprecedented time for the Earth right now," said Todd Dawson, a UC Berkeley professor and Save the Redwoods adviser.
A key question the researchers intend to answer – working at the top of 350-foot trees, in laboratories and in greenhouses — is where and how young redwoods can grow and flourish, said Steve Sillett, a professor of forest ecology at Humboldt State University.
"We know they are worth saving because they are so inspiring," Sillett said.
To begin getting answers, the scientists are carefully measuring and implanting hundreds of high-tech sensors among the redwoods and sequoias at 16 sites ranging from Jedediah Smith State Park northeast of Crescent City to the Sierras to Big Sur.
One of the monitoring sites, set to be established in the fall of 2011, is at Armstrong Redwoods State Natural Reserve in Guerneville.
"We've got to have Sonoma County in our study," Sillett said. "That's a puzzle piece we've got to have."
Armstrong Redwoods is a relatively small stand of old-growth redwoods, but it is in an environment vastly different from the redwood rain forest at Jedediah Smith park, he said.
The scientists gathered at Humboldt Redwoods park off Highway 101 displayed slender, low-tech tree coring rods and solar-powered weather sensors, called climate nodes, that send data wirelessly from the forest to the lab.
The cores reveal tree rings that experts use to date the redwoods and also contain carbon and oxygen isotopes that reveal climate conditions from throughout the tree's life. "It's a gold mine of information," said Anthony Ambrose, a researcher at UC Berkeley's Center for Stable Isotope Biogeochemistry.
Small probes attached to tree trunks measure how fast water is moving through the sapwood, the live portion of the tree just under the bark. Scientists then can quantify how much water the redwood consumes and how much carbon fixation it is achieving through photosynthesis.
"It's groundbreaking," Ambrose said. "It's never been done."
The research project is funded by Save the Redwoods, a San Francisco-based conservation group founded in 1918, with support from Ken Fisher, a billionaire money manager and redwoods advocate who graduated from Humboldt State University.
The redwood research wouldn't have gotten off the ground, literally, without Sillett's pioneering venture into climbing the tall trees, which started in the late 1980s.
With ropes and refined equipment, Sillett said, it has become "simple" to scale the redwoods and to move from treetop to treetop through the forest canopy.
"You can't learn about these trees from standing on the ground," he said.
Already, the project has yielded some surprises. The rate of wood growth in the Humboldt Redwoods park's ancient trees has doubled in the past century, Sillett said. That disproved the old notion that redwoods grow more slowly as they age. But it isn't clear what it means or what conditions prompted the growth, he said.
Despite their fame and status as Northern California's iconic tree, redwoods remain largely a mystery.
"There's so much ignorance about this species," Sillett said. "We want to change that."