The moment was at once historic and odd - a room filled with environmentalists standing and cheering Orange County's biggest developer.

Donald Bren had just announced during a private gathering a gift of 11,000 acres by The Irvine Co. as permanent open space, mostly in the canyons and hillsides of the Santa Ana Mountains north of the city of Irvine and east of Orange. Here was a man who had developed thousands of homes and millions of square feet of commercial office space and his legacy may be written on the earth he agreed to preserve forever.

"To me," he said to the gathered during the November 2001 announcement, "the great outdoors provides serenity." He wasn't speaking as a rich man who can fly anywhere to find it, but as an Orange County resident who takes flight on his bike along Newport's Back Bay.

"Through my entire life," Bren said in a recent interview, "I have treasured the outdoors and received sustenance from it. I am a fisherman, a sailor, a skier, a windsurfer, an occasional hiker and bicyclist. Great open spaces have always given me a sense of freedom."

The event 16 months ago, before 200 guests comprised of company management, environmental organizations and local and regional government officials, was unique. The 11,000 acres alone approach the size of the island of Manhattan, so when people talk, as they sometimes do, of the Irvine Ranch's open spaces being valued like New York City's Central Park, think bigger, much bigger. The gift also meant that more than 50 percent of the company's 93,000 acres will be forever open space, greenbelts and parks. Those 53,000 acres - now called the Irvine Ranch Land Reserve - are probably the nation's largest protected resource within a highly urbanized area. Bren is helping it along with a $30 million commitment to manage, preserve and restore the lands, and provide public access. Michael McKee, vice chairman and chief operating officer, noted during the evening that as company officials planned the gift, Bren kept telling them to push the open-space envelope.