Irvine Co. Agrees to Wilderness Plan : Environment: Accord with Nature Conservancy will protect 17,000 acres in Orange County. The development firm hopes to get mitigation credits in return.

IRVINE —  Calling it a historic and unprecedented alliance, Irvine Co. Chairman Donald Bren and a national environmental group announced Thursday that they have formed an unusual partnership to preserve some of Orange County’s richest wilderness areas and open them to the public within a year.

At a news conference under tents in pristine Shady Canyon on the vast Irvine Ranch, Bren outlined a two-year management plan that creates what he called a “unique and uncommon alliance” between his powerful Orange County land development company and the Nature Conservancy, one of the nation’s largest private conservation organizations.

The terms of the agreement call for the conservancy to manage 17,000 acres of undeveloped Irvine Co. property and begin the first phase of a stewardship plan to preserve the ecosystems that thrive there.

“Our goal is to . . . protect these natural resources in perpetuity, enhance the wildlife habitat areas found here and provide for early public use of this special land,” Bren said. “I believe this program offers us a special opportunity to make a lasting contribution to protecting California’s rich natural resources.”

Officials of the Nature Conservancy praised the agreement, which was the result of 18 months of study and consultation between Irvine Co. officials and the 41-year-old nonprofit organization based in Arlington, Va.

“To my knowledge, this is the first time in California and, for that matter, the first time in the nation that a private landowner has joined with a private conservation organization to protect and enhance significant natural resources,” said Walter Gerken, a Corona del Mar resident and chairman of the Nature Conservancy of California’s board of directors. “We are hopeful that it will become a model for other private landowners to study and emulate.”

The Irvine Co. has agreed to dedicate the lands in the reserve to the public over the next 20 to 25 years. For the first two years, the firm will pay all costs for managing the property, estimated at $440,000. Bren promised that together with other past and future land dedications, more than 30,000 acres of the 63,000-acre Irvine Ranch will ultimately be left as permanent open space.

In exchange for the dedications of land, the company hopes to accumulate environmental mitigation credits to be used in exchange for future development of Irvine Co. commercial and residential projects, said Monica Florian, an Irvine Co. vice president.

The 17,000 acres, called the Irvine Co. Open Space Preserve, are divided into three main sections:

* About 6,600 acres, called the southern reserve, include wooded areas such as Emerald Canyon and Boat Canyon and the shaded meadows between Laguna Beach and Irvine that stretch from the San Diego Freeway almost to the Pacific Ocean.

* The northern reserve consists of about 7,600 rugged acres east of Tustin and Orange, including hidden canyons highlighted by the Sinks of Limestone Canyon, a huge, steep-walled ravine that environmentalists have compared to a mini-Grand Canyon.

* The Weir/Gypsum reserve will consist of 2,800 acres in remote canyons south and east of Anaheim.

Public access will begin with docent-guided tours as early as next spring in the southern reserve area next to Crystal Cove State Park, and in the northern reserve in Limestone Canyon.

The reserve will protect coastal sage scrub, a fast-dwindling mix of vegetation found only along the California and Baja California coast. Among the many plant and animal species there is the ecologically sensitive California gnatcatcher. Developers along the coast, including the Irvine Co., have been sharply criticized in recent years by environmentalists for bulldozing vast stretches of coastal sage scrub.

Steve McCormick, executive director of the Nature Conservancy of California, said the agreement represents a departure from the organization’s normal method of doing business. Under most circumstances, the conservancy buys private parcels and preserves them by either establishing a reserve or selling the lands to an agency willing to protect them.

Officials in Laguna Beach, which borders the Irvine Ranch, also applauded the program. Mary Fegraus, executive director of the Laguna Canyon Foundation, called all of the designated lands “treasures.”

“In a sense, they are like time capsules,” said Fegraus, whose organization is helping the city raise $78 million to buy another Irvine Ranch parcel, the 2,150-acre Laguna Laurel. “No one has seen or documented what’s on these properties. Now maybe we will get a chance to do that.”