Two trees fell in a forest and, while no one was there to hear them fall, news of their collapse echoed across the country.
"You notice when a sequoia falls," said Al Nash, a park service spokesman in Washington, D.C. "These magnificent trees are so overwhelming, everyone notices when one falls."
Not only did the crashing of the two 200-foot high giant sequoia trees in late February make news, the incident has also cast attention on a dilemma facing park officials throughout the country: Is it possible to love parks too much?
The National Parks Service estimates that nearly 280 million people visit national parks each year for recreation. At Yosemite National Park, where the two sequoias toppled, between 3 million and 4 million people enter the park every year.
It's not yet clear what caused the two towering trees to tip — in fact, their toppling may have been completely natural. But officials said that human foot traffic could have been a factor.
Too much trampling around the trees' root systems can pack down the soil and block the flow of oxygen and water to the trees' roots. Some are also concerned that smog from car traffic inside the park degrades foliage of the trees and other vegetation.
To protect the park's remaining sequoias, other terrain and wildlife, some have proposed limiting both automobile and foot access to the park.
Keeping Cars Out
A controversial plan, devised during the Clinton administration, would reduce day-use parking by two-thirds, add shuttle bus service to replace car traffic, create more protections around trees' root systems and close some riverside camp sites. The proposal by the U.S. Environmental Protection Agency, is expected to be finalized next year after public comment.
"We need to make sure that visitors feel welcome, but at the same time we must make sure our resources are protected," said National Park Service Director Fran Mainella at a hearing about the plan in Yosemite National Park on Tuesday.
Yosemite National Park is one of a growing number of national parks across the country where officials have adopted or are looking to adopt new rules to restrict auto and some foot access to sensitive regions.
Snowmobile access to Yellowstone National Park has been curtailed, cars have been replaced by shuttle busses in the interior of Utah's Zion National Park and Montana's Glacier National Park in Montana. Even smaller parks, like Great Falls Park in Virginia, are adding traffic restrictions inside their gates.
"We're always trying to find the balance between accommodating visitors and protecting the resources," said Nash.
At Zion National Park and Glacier National Park, more frequent sightings of rare wildlife, including mountain lions, have suggested the new rules have made a difference.
Too Much Attention?
For the giant sequoias in Yosemite, reduced tampering could add hundreds of years to their life spans, say researchers. Giant sequoia trees can grow taller than the Statue of Liberty and can live for more than 3,000 years.
"As more of these trees become increasingly recognized because of their grandeur, more attention has to be applied to protect them," said Steve Sillet, a botany professor at Humboldt State University in Northern California, who specializes in coastal redwoods and giant sequoias. "Footsteps over time have a massive pounding effect to the trees' root systems."
Sillet points out that a giant sequoia that once ranked tallest in the park is now topped with a largely dead crown. He believes all the extra attention on the tree drew more visitors and compromised its ability to keep its leaves healthy.
"The trees can't move — they're stuck," he said, "so it's up to us to make sure they're kept from harm."
Park officials have been surrounding some of the oldest, largest and most historically significant trees with fences to keep the public from trampling root systems. But the two trees that fell in late February weren't among them.
Both of the fallen trees were estimated to be between 300 and 759 years old and stretched more than 200 feet into the air. Since the trees were located close to each other in the Mariposa Grove along the southern border of Yosemite National Park, officials say it's possible that one tree fell first and then brought the other down with it.
The last time a giant sequoia fell in the park was in 1998 when a young tree toppled for unknown reasons. Before that, the most recent giant sequoia known to have fallen was the grove's so-called Tunnel Tree, which collapsed in 1969. This massive tree had a tunnel carved through its center where cars once drove through, which weakened its structure and led to its demise.
Today, officials shudder at the thought of carving tunnels through the giant trees. In fact, in earlier decades giant sequoias were only valued once they were cut down for lumber. One reason giant sequoias still exist is because loggers found their wood to be too brittle for much practical use.
While the trees may not be at risk now from trunk carvers or logging, there has been an increase in day traffic to the park. Mainella says that over the last several decades, day use of the park has spiked dramatically, even though wildfires discouraged people from visiting the park last year. About 3.46 million visited Yosemite last year — 17 percent fewer than a 1996 peak of 4.2 million.
The Yosemite Valley Plan was designed to ease the impact of these visitors, although the $442 million blueprint remains controversial among merchants in the area who depend on tourism for their livelihoods.
Any effort to reduce the impact of human traffic in Yosemite is likely to improve the health of its trees and wildlife, Sillet argues. But, he adds, it is possible that human traffic had nothing to do with the falling the two trees in Mariposa Grove. Trees die, and sometimes the cause is completely natural.
"It could have just been a fluke wind," he said. "Those trees' canopies are so rough — they are giant crowns with lots of space between them. There's a chance a down draft caught a crown real hard. There's not much you can do about that."