California's massive, ancient redwoods have dealt with climate change before. But this time they might need our help.
By Edward Humes
A grizzled, eloquent John Muir wrote impassioned essays and lobbied the White House to save them. A century later, the intrepid, ethereal Julia Butterfly Hill perched in one for two years to hold off loggers. But these days, some of the most effective tools for protecting California's remaining giant sequoia and coast redwood forests are far more prosaic: a bow, an arrow, and a fishing line.
How else are the scientists studying the largest trees on the planet going to reach the topmost branches? The arrow arcs over a high branch, dragging the fishing line earthward (hopefully without embedding itself in the people below). The filament is used to pull a pair of stout ropes aloft. Then up go the researchers, using mechanical ascenders and mountaineering gear to poke through to a nearly separate ecosystem, even a different climate, from what they left behind at root level. Dangling beneath a canopy higher than the Statue of Liberty's crown, they've come to figure out how to help redwoods cope with climate change.
"These trees are a remarkable living archive going back millennia," says Todd Dawson, the University of California, Berkeley, scientist codirecting a three-year,$2.5-million redwood-climate research project. "But toget that data, you have to assess the entire tree. You have to get up in the canopy. You've never really seen the redwood forest until you do that."
The researchers' mission is to reveal the hidden lives of these ancient trees--especially in their seldom-visited upper reaches. With diminishing snowpack in the Sierra and decreasing fog along the coast, redwoods face a hostile future and a worst-case scenario that could result in more Sequoioideae museums than functioning forests.
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There's something about being near a mature coast redwood, its spire impossibly tall, or a broad sequoia, with its lava flow of soft, knobby bark, that evokes a visceral response. It's less like viewing a tree and more like stumbling on a geologic wonder, an arboreal version of the Grand Canyon or Niagara Falls. People use their library voices while walking among redwoods. Maybe it's being in the presence of something that can outlive 50 human generations--a single tree, standing now in the Sierra Nevada, born during the Bronze Age, and whose grandfather shed its cocoa-colored cones before recorded history.
Or perhaps it's simply their size. Coast redwoods have topped 375 feet, more than a football field upended, end zones included. Their giant sequoia cousins aren't as tall but are thicker and bulkier. The famous General Sherman Tree in Sequoia National Park is the biggest tree in the world: 35 feet wide at its base and 275 feet tall; it contains 52,500 cubic feet of wood--enough to build a subdivision of 40 four-bedroom houses.
Even in death, the redwoods are beyond imposing. The fallen logs last with minimal decay for hundreds of years because of the unique fire and rot resistance of mature redwood. The more remote forests are full of them--grounded whales of wood. Around the time of the California gold rush, two homesteads and a saloon were built inside a fallen redwood. Soldiers used another for a stable.
The coast redwoods are by far the more numerous of the West's redwood species, ranging from central California to southern Oregon, always within 50 miles of the Pacific, where the fog offers sufficient moisture to get the trees through dry summers. Only about 4 percent of the old-growth coast redwoods remain; the rest have been lost to a wave of logging and development that began in the mid-1800s. San Francisco was built with those forests, burned down, and was built with them again. Though not as heavily logged, the iconic giant sequoias are less numerous, restricted to a small string of groves in the Sierra Nevada where the right combination of temperature and snowmelt allows them to thrive.
These redwood cousins, despite their longevity and resiliency, are threatened by climate change--a human-caused crisis that may require a human-conceived solution. Fog and snowpack are declining, while fire seasons are getting longer and hotter, according to redwood researchers. Ancient pollen counts suggest that the trees experienced a severe population decline between 10,000 and 4,000 years ago, a period when the average temperature was 3 to 4 degrees warmer than it is today. Carbon dating of sediments from that era shows very little sequoia pollen, which means that our impending warming trend could create a similar meteorological hazard for the trees. Dawson hopes his research will result in strategies for helping the trees cope with rapid climate change, but definitive answers are years away. Meanwhile, environmentalists and the government agencies in charge of national parks and forests are left grappling for (and scrapping over) more immediate solutions.
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The conflict over how best to respond to climate threats to redwoods may be headed for an initial showdown at the Giant Sequoia National Monument in the Sierra Nevada.
President Bill Clinton carved the monument out of national forest land in 2000 as a means of better protecting its giant sequoia groves. But environmentalists from the beginning have objected to the U.S. Forest Service's preference for using logging as a way to manage the forest and safeguard against fire risks. The Forest Service has advocated logging the smaller trees (not redwoods) that grow among the sequoias to support the germination of new sequoia trees and eliminate the saplings' competition for water and sunlight.
The Sierra Club and other groups have challenged this approach as unscientific and possibly harmful to the sequoias' survival chances. As a result of lawsuits brought by the Club and other groups, a federal judge in 2006 declared the Forest Service's management plan for the monument "incomprehensible," forcing it to develop a new one.
The Forest Service's work on a replacement plan, which still calls for extensive logging to protect sequoia groves, concluded its public comment phase in December. Joe Fontaine, a longtime activist with the Sierra Club's Kern-Kaweah Chapter in Bakersfield, California, says environmental groups have also panned the new plan. He asserts that the Forest Service's plan ought to mimic the National Park Service's approach in Sequoia National Park, where controlled fires, rather than logging, have been used successfully for more than 40 years in helping the sequoia groves thrive.
Redwoods and sequoias--with their insulating bark and tannin-impregnated wood--use forest fires to procreate. After a fire clears out the under-story, says Nate Stephenson, a forest ecologist with the U.S. Geological Service in Sequoia and Kings Canyon National Parks, the trees' seedlings take off, triggering a population explosion. Ste-phenson, who's been studying the trees for 30 years, says fire is central to sustaining healthy sequoia forests. A longtime practice of suppressing fires, intended to protect redwoods, has instead made them more vulnerable.
Stephenson and the USGS are working to pool the arboreal resources of various federal land-management agencies and colleges to develop a unified response to global warming--rather than the piecemeal, sometimes conflicting methods now in place. For the Giant Sequoia National Monument, however, environmental groups have suggested transferring oversight to the National Park Service. "The Park Service has done an excellent job of managing the sequoia ecosystem and adjusting conservation strategies to address climate change," says Sarah Matsumoto of the Sierra Club's Resilient Habitats campaign, who cites the Forest Service's "history of poor management" of Giant Sequoia.
There is a growing sense of urgency behind these proposals. Stephenson is part of an ambitious monitoring project of all types of trees in Sequoia National Park. One of the project's key findings is that the arboreal death rate has doubled in recent years--a worrisome trend that seems to correlate with a warming climate. He is designing a study specifically for sequoias, which are too sparse to have been represented sufficiently in the forest-wide study. For a tree so revered, Stephenson says, there is alarmingly thin long-term data about how environmental changes affect sequoia birth and death rates.
Meanwhile, the research that seems to be creating the most excitement among self-professed "redwood geeks" is happening 30 stories above the forest floor. There, crown-scaling scientists like Dawson and Stephen Sillett, who heads the Institute for Redwood Ecology at Humboldt State University, are among the first to gauge the health of entire trees, from roots to canopy.
Surveying a single tree can be a daunting task: It takes six people three days to map one massive redwood tree top to bottom, branch by branch, inside and out, with tape measures and core samples, cone counts and leaf inventories. Some of the larger branches can be as big as trees themselves, so old and fertile that ferns, plants, critters--even other trees--grow on them, forming a forest within a forest high above the ground.
The researchers are measuring trees in sixteen 2.5-acre plots scattered up and down California, encompassing the entire range of environments in which sequoias and coast redwoods live. They use computers to construct a 3-D simulation of each tree, charting its physiology and measuring growth rings to gauge its response to past and present climate shifts. Over time, the study's findings could be used to craft strategies for maintaining existing groves and for selecting areas where new forests might have a better chance of survival if climate change accelerates.
The study has already shattered some long-standing misconceptions about redwoods. Contrary to popular belief, the oldest trees, far from becoming doddering retirees, produce wood at a rate comparable to that of young trees. "People used to think that old trees were just sitting there clinging to life," Sillett says, "but they are producing a lot of wood. A lot of wood." This means that each redwood is an important and ever-expanding link in the carbon-absorption chain.
Ruskin Hartley, executive director of the Save the Redwoods League, says the redwoods are the kind of living icons that motivate environmentalists to take action. He believes that people are changed just by being near them, by connecting with their living history.
"Redwoods have been on the planet for more than 100 million years. Individual trees have lived 2,000, 3,000 years. And they have seen a wide variety of climate," Hartley says. "What they have never seen is what's projected for the future: the rapid pace of climate change, at a time when they've already experienced sweeping environmental changes, from logging to invasive species to development. And that's really the maelstrom we're concerned about. How are they going to get through this?"
EDWARD HUMES's last story for Sierra was "Latest From the Labs" (September/October 2010).
This article was funded by the Sierra Club's Resilient Habitats campaign.