A renewed view of some of the world's oldest trees

For three years, some of the most striking examples of these towering marvels were off limits to visitors in Yosemite National Park. After a $40 million renovation — the largest restoration project in the park’s history — the Mariposa Grove, a collection of around 500 mature giant sequoias, reopened last week.

What Muir called a “forest masterpiece” is now back on display.

The renovation addressed a problem that the park has struggled with for years. On the busiest summer days, more than 7,000 cars may converge on the park, which is about a four-hour drive from San Francisco. The gridlock they create amid the stunning chutes of water running down the steep granite slopes of Yosemite’s glacier-carved valley results in a kind of drive-by naturalism that frustrates many.

In the Mariposa grove, which is a 45-minute drive from the Yosemite Valley floor, the traffic brought exhaust fumes and engine noise to the foot of some of the world’s oldest living things. Park rangers feared that the asphalt covering the root systems of the trees could damage them.

One of the trees in the grove, the Grizzly Giant, a massive, battered and gangly sequoia, is estimated to be 1,800 years old (“plus or minus a few centuries,” according to the National Park Service). Early last week, just a few days before visitors were welcomed back into the grove, a deer was calmly enjoying the shade of the trunk, which measures nearly 100 feet in circumference, one-third of a football field’s length.

Partly financed with a $20 million gift from the Yosemite Conservancy, a private philanthropic organization, the renovation involved ripping up nearly 1 1/2 acres of pavement near the trees where cars and trams would pass and replacing it with walking paths made of packed dirt held together with resin. Visitors are now encouraged to take a free shuttle bus from a new parking lot a 10-minute drive away (there is still some accessible parking for disabled visitors at the grove itself). The clanging, smoke-spewing diesel trams that previously took visitors on a tour of the grove have been removed.

“We are not trying to take away anyone’s freedom,” said Scott Gediman, a spokesman for the park. “Take your car, but then park it. And walk.”

With bark that can be more than 1 foot thick and high levels of tannins to repel insects, giant sequoias are regarded by experts as some of the world’s most resilient trees. Close to 130 million trees of other species died in California over the past decade after being weakened by a five-year drought, but no mature giant sequoias perished, according to Sue Beatty, a restoration ecologist who helped lead the project. Even so, Beatty and other experts said they saw some signs of stress in the sequoias.

Giant sequoias do not have a central taproot. Instead, they develop a shallow network of roots, around 3 feet deep, that spreads as far as 200 feet from the trunk, Beatty said. The asphalt and the trampling feet of visitors in the grove were making the trees more vulnerable.

“This project was all about the trees,” she said. “We wanted to improve their survivability in the time of a changing climate.”

In the main viewing areas, the trees are cordoned by pine fences, although visitors can get up close to the trees in the upper parts of the grove. Culverts were torn up and creeks and wetlands were restored.

Frank Dean, a former park ranger who is head of the Yosemite Conservancy, describes the renovation of the grove as part of an evolution in the way Americans approach the West: from conquest and discovery to preservation.

Early visitors to the Mariposa Grove bored through at least one giant tree, which today is aptly called the California Tunnel Tree. Visitors can still walk through the trunk.

“There’s a greater understanding of how special — and how fragile — it is,” Dean said of the flora and fauna in the park. “Society has evolved. It’s a lighter-on-the-land approach.”

Yosemite receives around 5 million visitors a year. The park is balancing its mission to attract visitors with a need not to be overwhelmed by them, said Gediman, the ranger.

“The whole idea of, ‘Here’s an attraction, let’s build a parking lot next to it’ — we’re not doing that any more,” he said.

Yosemite isn’t finished with parking lots: a new one for the Mariposa Grove shuttle terminal holds 300 cars. But they are being built farther from the park’s most stunning attractions.

Muir, whose writings helped alert Americans and the world to the beauty of Yosemite and the importance of preserving it, would probably be put off by the crowds of today. But he would recognize his favorite trees, which he described as immortal and which look very much the way he saw them 150 years ago.

“These colossal trees are as wonderful in fineness of beauty and proportion as in stature — an assemblage of conifers surpassing all that have ever yet been discovered in the forests of the world,” he wrote. “Here indeed is the tree-lover’s paradise.”

This article originally appeared in The New York Times.