Yosemite Valley: A unique place
Standing in Yosemite Valley, geologist Greg Stock talks about the 3,000-foot cliffs he sees every day — the 100-million-year-old granite, the glacial sculpting, the best panorama on the planet.
Then he catches sight of that monstrous flat-faced dome and stops mid-sentence. He's been the Yosemite National Park geologist for eight years, but Half Dome still steals his thoughts.
"Half Dome is a freak of nature," says Stock, co-author of a 2010 book explaining the park's geology. "We have theories, but no one really knows exactly how it came to look like this. I find myself taking a lot of pictures of it. How can you not look at it?"
Half Dome and the grand vista around cozy Yosemite Valley are good reasons to practice science here, but researchers see a much bigger picture. Yosemite is a living laboratory — the entire 1,169 square miles, not just the gorgeous 7 square miles of Yosemite Valley.
It's a Sierra Nevada time capsule. Mining, hunting, logging and commercial development have been largely kept out since the late 1800s. Yosemite is a spectacular connection to the Earth's past and, perhaps, a key to understanding nature's future as the climate warms.
Scientists need little prompting to cheer this month's 150th anniversary of the Yosemite Land Grant, which protected the valley and the Mariposa Grove of giant sequoias. The ceremony for the 150th is June 30, but scientists have been celebrating for more than a century.
Among Yosemite's millions of annual visitors is a cadre of world-class researchers studying rocks, glaciers, streams, snowpacks, insects, plants, animals and fire behavior. Some scientists drop by just because it's Yosemite.
Three years ago, biologist and science icon E.O. Wilson — Harvard University professor emeritus and eloquent winner of two Pulitzer Prizes — visited the park. He spoke at length to fascinated rangers, researchers and visitors about biodiversity in places such as Yosemite.
Another leader in science and regular park visitor is biologist Norman Christensen, Duke University professor emeritus, Fresno native and national authority on ecosystems. He said Yosemite and other national parks are increasingly becoming islands of nature as the world changes.
"If you're going to study climate change, you need a long-term record of nature," he said. "Yosemite is one of those places. This is a very important place."
David Graber, retired chief scientist for the Pacific West Region of the National Park Service, started his research career in Yosemite four decades ago, studying black bears. He said national parks such as Yosemite are a precious resource.
"How else would you study old-growth forests and animals?" he asked.
Extensive old growth
"Old growth," which is basically an undisturbed, mature forest, is watched carefully at the 63-acre Yosemite Forest Dynamics Plot. Magnificent sugar pine, white fir and red fir grow here.
Some trees in the plot are 5 or 6 feet in diameter. Some were seedlings in the early 1600s.
Led by Utah State University ecologist James Lutz, researchers are tracking 35,000 trees — each one of them — in the Forest Dynamics Plot near Crane Flat, at the western edge of Yosemite. The area was burned in the massive Rim fire last year.
Fire managers softened the blow of the Rim fire for the research plot by setting smaller back fires to eliminate brush that might have helped the blaze level everything. An estimated 12,000 trees died, but the research plot survived.
The blaze might have done some good for the ecosystem, researchers said. In its natural state, the Sierra needs smaller, brush-clearing fires every 10 to 25 years to keep forests open, healthy and growing. But for many decades, federal policies called for snuffing every fire, allowing choking vegetation to set the stage for larger, more destructive blazes such as the Rim fire.
For decades, Yosemite has been among the leaders in researching fire's role in a healthy forest, advancing the idea of making forests safer with small, intentionally set fires.
Likewise, the Forest Dynamics Plot, one of less than 50 large, monitored forests in the world, will advance the understanding of old-growth forests and perhaps discover keys to protecting more of nature as the climate warms.
"The Forest Dynamics Plot is very large, very extensive old growth," said Lutz, who started the monitoring program in 2009. "It is absolutely phenomenal."
Don't look for quick scientific breakthroughs here on such issues as the increasing disappearance of large, old trees in old-growth areas. As part of the Smithsonian Institution Center for Tropical Forest Science network, the idea is to track these trees and find out their fate over time.
"It takes 500 years to grow some of these trees and sometimes only one storm to knock one over," said Lutz. "We want to be there each year for decades to do full pathology on trees and find out how they died."
Many creatures, such as the spotted owl and the cat-like Pacific fisher, depend on old-growth forests. Plant and insect communities have developed over centuries around the massive trees, snags and fallen wood, which can remain in the ecosystem for many decades.
What will happen to the forest as the climate warms? Trees could become more susceptible to bark beetle infestations. Some creatures may be forced to locate elsewhere.
"There's a lot we don't know about old-growth forest," Lutz said. "This kind of research takes time. That's why we have many researchers younger than I am to carry on as the decades pass."
Biodiversity a big deal?
Why should people care about old-growth forests, biodiversity and nature research? Scientists cite many reasons, but the simplest ones are often the most compelling.
Healthy air and water are at the top of the list. The forest is an elegant filter for the two most important parts of healthy human living. It makes the diverse, 400-mile Sierra ecosystem a high priority for California, scientists said.
Botanist Alison Colwell, based at the U.S. Geological Survey field station at Yosemite, added: "You never know where the next drug breakthrough will come from. Remember, penicillin came from mold on bread."
Discoveries are made regularly in Yosemite. In her efforts to document plant life and diversity at the park, Colwell found a previously unknown orchid species in Yosemite Valley. She was alerted by a distinctive scent from the plant, now known as the Yosemite bog orchid.
"It stinks," she said. "It has the chemical profile of scat."
Such discoveries continue, in part, because Yosemite was set aside 150 years ago, she said. The Sierra is a hotbed of biodiversity because of its Mediterranean climate, rich soils and abundance of life zones along different elevations.
Deep river canyons throughout the Sierra form barriers that help to isolate populations of life and force them to evolve faster, she said. The newer species quickly adapt.
She said the diversity of organisms can be appreciated for beauty and wonder. The park has more than 400 species of vertebrates, including fish, amphibians, reptiles, birds and mammals.
But there are other good reasons to appreciate the diversity, Colwell said. Diversity makes the region more resilient as the climate warms, perhaps preventing huge losses of species in the Sierra as the climate warms, she said.
Yosemite's protected landscape may create a safe harbor for many creatures.
"There will be a lot of places for many species of life to shift and survive here," Colwell said.
Half Dome, Yosemite Valley
Yosemite's global image is a silhouette of Half Dome. In terms of sheer size and celebrity, there's nothing quite like the dome and the geology in Yosemite Valley, said geologist Stock.
The granite cliffs topped by spires, domes and soaring waterfalls are clustered around a U-shaped valley.
In a quick windshield tour, you can see El Capitan, Bridalveil Fall, Cathedral Rocks, Leaning Tower, Three Brothers, Cascade Arches, North Dome, Half Dome and 2,425-foot Yosemite Falls, the tallest waterfalls in North America.
Just one or two of those features would turn most any mountain area into a coveted travel destination anywhere in the world. Many first-time visitors say Yosemite Valley looks almost unreal, like a painting.
But it's even more amazing than most people know, Stock said. Consider that sediment has been filling the valley for many thousands of years, concealing a much deeper valley.
"The bottom of Yosemite Valley is another 2,000 feet below the ground level," Stock said. "These cliffs are really more like 5,000 feet tall. That's just incredible."
How did it get this way?
Conservationist John Muir must have wondered the same thing in the 1870s. Though he was not a trained geologist, he was the first to theorize the impact of glaciers in Yosemite Valley.
He also was the first to identify a glacier in the park — Maclure Glacier near Mount Lyell. There are many small glaciers in the park and along other parts of the jagged Sierra crest. Scientists say they are steadily melting away.
Yosemite's glaciers are not remnants of the last Ice Age, which ended about 10,000 years ago. Instead, they date back only a few hundred years to the Little Ice Age, a time of brief global cooling that ended around 1850.
Today, Stock and other geologists continue to ask how Yosemite Valley got this way. They look deeper in history for answers.
Yosemite Valley's granite began as molten magma 100 million years ago, researchers say. It slowly cooled below the Earth's surface, crystallizing into granite while a tall volcanic range rose above it. Erosion over many millions of years removed volcanic rock above the granite. The range uplifted again about 10 million years ago.
Glaciers and their icy magic didn't come along until about 1.5 million years ago. The dramatic domes and spires along the rim of Yosemite Valley are really a recent reshaping of granite that has been around a lot longer.
So does that mean a big slice of Half Dome just fell off one night?
"No, it most likely happened slowly over time with glacial erosion, exfoliation of the granite and rock fall," Stock said. "Half Dome is still an enigma. But people all over the world recognize it instantly."