Public Gets Invitation to a Secluded Canyon : Wild lands: After three years of negotiations, Irvine Co. opens Limestone Canyon to guided tours. About 17,000 nearby acres, long off-limits to people, will eventually become Orange County parklands.

Deep in this secluded canyon, time is measured in centuries, even millennia. Little has changed in the 4 million years since a stream began carving an eternal path through the sandstone cliffs.

Yet for more than 100 years, few people have set foot in this secluded, ancient place called Limestone Canyon. Until now, its visitors, almost exclusively, have been limited to the descendants of rancher James Irvine and their successors at the Irvine Co., headed by Chairman Donald Bren.

One morning this week, Orange County’s wealthiest developer donned scuffed brown suede boots and blue jeans to share the canyon with the public for the first time.

“This is a special day,” Bren said before embarking on a two-hour tour led by Nature Conservancy docents. “This is the first time in the 129-year history of the ranch that we’ve opened up land, for the people of cities, for the people of urban areas. For everyone.”

Starting today, weekly guided tours will be held in this lush, rugged terrain. It marks the public’s first access to the Irvine Company Open Space Reserve, a network of 17,000 acres owned by the Irvine Co. but bequeathed to the county as future parkland.

This weekend’s inaugural hiking, biking and equestrian tours of Limestone Canyon are the culmination of three years of negotiations by the Irvine Co. and the Nature Conservancy, an environmental group known for managing and restoring rare ecosystems.

Nearly five years ago, Bren got the idea to open the land to the public as soon as possible, rather than wait up to 20 years for it to pass into government hands. The land gradually will be turned over in exchange for Irvine Co. development rights on adjacent lands.

“Look around,” said Cameron Barrows, the Nature Conservancy’s Southern California area manager, as he stood next to a wooded stream in Limestone Canyon, “because this is what Orange County and Southern California used to be. There are no other areas that will be protected like this.”

The Irvine Co. Open Space Reserve, split into a northern and a southern section, includes wilderness areas in and around Orange, Laguna Beach, Newport Beach, Irvine and Anaheim.

The northern reserve is a diverse, rugged landscape of centuries-old trees, streams and sandstone formations. The southern reserve rings Crystal Cove State Park in the coastal hills between Newport Beach and Laguna Beach.

Two new county parks--Peters Canyon in the Tustin area and Laguna Coast Wilderness Park--also opened in the past month on land formerly owned by the Irvine Co.

Environmentalists say the Irvine Co. is giving them a rare opportunity to restore entire ecosystems that have nearly disappeared from Southern California.

Still, years of work remain to reverse the ecological damage done by a century of cattle ranching. The Nature Conservancy hopes to gradually return the lands as much as possible to their natural state, making them even richer homes for a diversity of wildlife from mountain lions to rare lizards.

“This is a unique and farsighted goal that the Irvine Co. has,” Barrows said. “If other landowners can do that, we can perhaps deal better with our environment and endangered species issues.”

About 1 1/2 years ago, the Irvine Co. removed most of the cattle, since cows tend to chew up native grasses, bring in weeds and unwanted foreign grasses and erode stream banks.

“The company has been involved with this land for about 125 years, running cattle and some sheep,” Bren said, “and because of that, the land hasn’t been open to the public. People don’t mix with a commercial cattle operation. But as we de-emphasize cattle . . . we can now open some of this land to the public.”

On a breezy, sunny morning, Bren walked for 45 minutes through Limestone Canyon with about a dozen guests. He especially relished the docents’ tales about the history of the area, which was populated by Gabrielino Indians and early ranchers who lost 75% of their cattle to grizzly bears.

“These canyons, on a daily basis, rang with confrontations between man and beast,” Bill Walton, one of the Nature Conservancy’s volunteer docents, told the group.

Limestone Canyon is just a mile or two from the red-tiled roofs of the Irvine Co.’s Tustin Ranch and other nearby developments, yet it is worlds apart. Its sycamores stood untouched for two or three centuries. A stream has carved a huge bowl-like formation, called The Sinks, out of the sandstone.

Once traversed by grizzlies and wolves--species long extinct in Southern California--Limestone Canyon is still home to mountain lions, bobcats, coyotes, rattlesnakes, hawks, owls and other wildlife.

Because restoration is “more art than science,” Barrows said, the work will be done gradually over many years.

“We need to think about hundreds of acres at a time,” Barrows said. “Next year, we’ll probably start experimenting, but large-scale restoration may be two or three years off.”

More Open Space

Public access to a portion of the new Irvine Co. Open Space Reserve begins Saturday, with guided tours of Limestone Canyon, including the Sinks and Drippings Springs. Emerald Canyon in the southern reserve will open for guided weekend tours in a few weeks. A total of 17,000 acres of land with lush natural resources and scenic landscapes have been set aside by the Irvine Co. as permanent reserves.

The Lay of the Land

What: Guided tours of Limestone Canyon

When: Every Saturday

How much: Free

Who: Led by volunteer docents trained by the Nature Conservancy

How: By reservation only

For whom: Weekly hikes, starting out at about two hours, are limited to groups of 20. Separate guided mountain bike tours for up to 20 riders twice per month; guided equestrian tours for up to 10 riders on a request basis.

Information and reservations: (714) 832-7478, 3 to 5 p.m. Monday through Friday. Reservations should be made two weeks in advance. Tour lengths, itineraries and locations will change based on weather and fire conditions, visitors’ skill levels and impact on natural habitat.

Limestone Canyon

Opens today: Home to some of the county’s richest oak and sycamore woodlands. Has a 250-foot-deep sandstone formation called The Sinks, carved by a stream over millions of years.

Emerald Canyon

Green rolling hills and canyons are mostly coastal sage scrub, the mix of sagebrush and other shrubs that are home to the California gnatcatcher. Ridgelines have sweeping views of the Pacific Ocean.

Sources: The Irvine Co., the Nature Conservancy