YOSEMITE NATIONAL PARK -- Ah, the sounds of Yosemite Valley. Birds tweeting. Waterfalls crashing. Chain saws whirring?
The problem, they say, is that for thousands of years, fires ignited by lightning or set by Indians kept a balance between oaks, open grassy meadows and conifer trees.
But ever since President Abraham Lincoln set aside Yosemite for protection in 1864, people have put out wildfires. And without regular fire, ponderosa pines, incense cedars and other trees have grown unnaturally thick, choking out oaks and overtaking meadows. Not to mention, postcard images.
Now, iconic views captured generations ago by photographers like Ansel Adams or Carleton Watkins and painters like Albert Bierstadt are being lost, parks officials say, and must be preserved, similar to the way the National Park Service preserves wildlife or historic buildings.
"We are looking to remove the minimum number of trees in the most ecologically sensitive ways," said Kevin McCardle, a historical landscape architect at Yosemite.
"We have to find a balance because we are preserving these places for the enjoyment of the public and future generations," he said. "Enjoyment means allowing people to connect with nature. But you have to be able to see it."
The plan, however, is prompting shudders among some shutterbugs.
"I'd be upset if I saw people here cutting with chain saws. It takes away from the ambience of the park. It could disturb the animals," said Melissa Ziering, of San Luis Obispo County, who snapped photos near Bridalveil Falls on Thursday with her husband, Scott Ziering, and daughter, Maya, 3.
Not far away, Chris Jones, of San Francisco, took in the view of El Capitan.
"This is the first time I've been here, and the views look good to me," he said. "It's kind of weird to think they'd chop down the trees for a photo op."
Next month, after nearly three years of study, the park is scheduled to release the final details of its "Scenic Vista Management Plan."
After several public hearings, park planners ranked 181 scenic vista spots in Yosemite, including landmarks such as Tunnel View, Valley View, Yosemite Falls, Half Dome and Washburn Point. They found that in 28 percent of the locations, the historic view was completely obscured, and in 54 percent it was partially blocked.
The park's preferred solution calls for clearing and thinning trees at 93 locations over the next decade. Work would begin in 2012, with cutting only taking place in September and October -- after bird-nesting season, but before bat hibernation.
All wilderness areas, which means 95 percent of the park outside of Yosemite Valley, Wawona and a few other spots on the Tioga Road, would be exempt. And no trees older than 130 years would be cut.
Still, the work is expected to result in thousands of evergreen trees being axed, some as large as 100 feet tall and more than 30 inches around.
"We're not clearing big areas, and we're only doing it at certain periods of the year," said McCardle. "If a wildlife biologist says, 'You can't cut these trees because there are endangered species or other concerns,' we won't do it."
Contractors under the supervision of park biologists would clear spaces between 30 and 90 feet wide in key overlooks, vista points and other viewing areas, and then thin trees on the sides to blend with the surroundings. All tree stumps would be buried, and native plants and shrubs would be replanted.
In most cases, only ponderosa pines and incense cedars would be cut down. Black oaks would be left untouched, along with sugar pines, which park officials say have greater wildlife value, and rare white bark pines. Because the 93 locations range from less than one acre to 10 acres, the total tab could run into the millions at a cost of about $10,000 per acre.
Environmental groups mostly support the plan.
"Delaying action," wrote Alan Carlton, chairman of the Sierra Club's Yosemite Committee, in a letter to the park, "will only exacerbate and complicate future restoration efforts when removing large maturing trees blocking viewsheds will become an increasingly problematic issue."
The chopped wood would either be chipped and used in the park, given to local residents for firewood or sold by the tree-cutting contractors or commercial timber companies, McCardle said. It probably won't be burned because state air officials have raised concerns about smoke generated from the park's annual controlled burns to reduce wildfire risk.
Other national parks are watching the issue closely.
Although some parks, including Acadia in Maine and Shenandoah in Virginia, regularly clear brush and trees to improve views, most clearing has occurred in the national park system at Civil War battlefields, in places like Gettysburg or Fredericksburg, to preserve the views that Robert E. Lee and other generals saw from hilltops during key battles.
"It's a tough one. I think people will come down on all sides," said Kurt Repanshek, editor of National Parks Traveler, a leading website that covers national park news. "Some will say it's great. Some will say how can you dare cut down a tree?"
The issue may be easier to explain to the public at Civil War battlefields than large Western parks, he said.
"If you are worried about trees blocking vistas of Yosemite Falls or Half Dome, what about the man-made footprint that you put there?" he said. "It almost seems hypocritical; we're worried about the vegetation, but we've put up multistory lodges and grocery stores. Where do you draw the line?"
Some of the most famous spots, like the site in Yosemite Valley where photographer Carleton Watkins took a historic portrait of El Capitan in 1868 -- a photo later used on a renowned 1934 one-cent postage stamp -- are nearly completely obscured now by trees. But locations like that along waterways will not be thinned until park planners complete the Merced and Tuolumne river plans, which could mean that work is five years away, said McCardle.
Three years ago, park crews cut down several large trees at Tunnel View, which blocked one of the most panoramic views of Yosemite Valley, a place made famous by a 1940s Ansel Adams photograph in winter. That work has mostly been well received.
On Thursday, Erhirt Katzer, a tourist from Austria, said a similar debate arose in his country over plans to remove some trees to improve views of the Alps.
"At first, people said no, don't do it," Katzer said. "But after it happened, most said it was a good decision. At first visitors here might say it's no good, but then their photos will be nicer and they won't mind."