The Battle of Santa Rosa Plateau : Environment: A developer and conservationists will face off before the Riverside Board of Supervisors over grassland that is considered an ecological jewel.

The Santa Rosa Plateau is an ecological jewel, an oasis in the sprawl of subdivisions carpeting southwestern Riverside County. Perched in the Santa Ana Mountains above Murrieta, the plateau is a remnant of old California--acres of rolling, native grassland dotted with dense groves of rare Engelmann oak trees.

The Nature Conservancy was so taken with the site that it purchased 3,100 acres and created a preserve there in 1984. More recently, UNESCO recognized the plateau’s extraordinary wealth of flora and fauna by including it in a “biosphere reserve,” a distinction enjoyed by only three other regions in the state.

“This is not just a neat place; it is an extremely special place with ecological value that extends far beyond the Riverside County line,” said Jon Keeley, a botany professor at Occidental College.

Won Sang Yoo shares Keeley’s enthusiasm for the site, but for entirely different reasons. The Temecula developer owns 3,855 acres of the 15,000-acre plateau and believes--to the horror of Keeley and other preservationists--it is the perfect setting for thousands of homes and condominiums, a community he plans to call Santa Rosa Springs.

“We see the opportunity here to create a state-of-the-art project where people live as part of the natural environment,” said David Dillon, director of land development for Yoo’s firm, Ranpac Communities.

A week from today the Riverside County Board of Supervisors will step into the fray and determine which vision of the Santa Rosa Plateau will triumph. At a hearing on a blueprint for land use in the county’s southwestern corner, the supervisors will decide whether to increase building densities on the plateau to a level where it would be profitable for Ranpac to develop it.

The meeting will cap a mushrooming battle that veteran environmentalists say is as vitriolic as any they have seen in years. Two citizens groups have formed to circulate petitions, raise money and lobby for preservation of the plateau while the developer has spent thousands of dollars on consultants charged with softening the project’s impact on the environment.

Conservationists have produced letters from nationally recognized experts as testimony to the plateau’s uniqueness while Yoo has brought in public relations help and released a poll suggesting that more of the region’s residents support his project than oppose it.

While the confrontation mirrors battles waged time and again throughout Southern California, many warriors describe this one as a symbolic last stand of sorts in rapidly growing Riverside County.

“The level of activity suggests a feeling that if we don’t set aside some of these large tracts as permanent open space soon, there will simply be nothing left to protect around here,” said Bill Havert, a parks consultant who has championed numerous environmental causes in the Inland Empire.

So what makes this place worth fighting over?

Opponents of the development say the plateau’s stellar lineup of animal and plant life make it too valuable an ecological treasure to sacrifice.

Among its botanical highlights are the Engelmann oaks--majestic, olive green trees that differ from live oaks in color and shape. Engelmanns were once common from the Mexican border to the Santa Monica Mountains. Today, only the plateau is said to host dense woodlands of any significance.

Critics also say Ranpac’s project would wipe out 4,000 acres of native California prairie containing the largest intact parcel of the purple needle grass, bluegrass and other native grasses remaining anywhere.

“Nearly all of California’s native grassland has been destroyed by the introduction of foreign species,” said Gary Bell, manager of the Nature Conservancy preserve at the plateau. “What we have here is a large stretch in better condition than any I’ve seen.”

That grassland doubles as hunting grounds for much of the wildlife found on the plateau, which is home to numerous threatened or endangered species. Mammals like badgers and mountain lions are common. An estimated 132 species of birds--including two pairs of nesting golden eagles and the vanishing burrowing owl--also inhabit the plateau.

Ranpac officials say they have gone to great lengths to create a project that respects the plateau’s natural features, from minor moves like painting homes in earth tones to more important measures designed to ease the shock to wildlife. Developers note that 2,000 acres of their land will be left as passive open space--most of it sloping, chapparal-covered terrain--while another 400 acres will be parks and a golf course.

All but 10 of the 2,400 oak trees on the plateau will be preserved, with development snaking around them. The builders have also monitored the habits of wildlife to determine their routes of travel to feeding grounds and water. To preserve one heavily traveled canyon slated to be crossed by a new road to the project, developers have pledged to construct a $2.1-million bridge rather than simply fill in and pave over the canyon.

As for other corridors that will inescapably be blocked by houses, Dillon said the golf course will serve as a natural walkway for mountain lion, deer and other creatures: “People say, ‘What? A golf course as a wildlife corridor?’ You’d be surprised how well it works,” Dillon said.

All in all, he said, “we’ve taken extraordinary measures by today’s standards to be environmentally sensitive.”

Conservationists, however, say that even the best intentions can do little to minimize the sheer mass of the project, which includes commercial centers, schools and new roads and will change the plateau’s character forever.

“If they were building down in the valley, or anywhere else, I wouldn’t care,” said Beverly Burns, 36, of Lake Elsinore, who leads schoolchildren on nature walks at the scenic spot. “But to build here, to ruin this, is just criminal.”

Dan Silver, a Los Angeles physician who frequently drives to the plateau to enjoy the Engelmann oaks, agrees.

“They make a big deal about saving these oak trees, but that isn’t the point,” Silver said. “Unless you have groves of reproducing trees and a beautiful setting surrounding them, then you really have nothing.”

Project opponents are pushing the county to buy the plateau and create a regional park. Dillon said Ranpac will entertain offers for the land but will not put plans on hold while conservationists search for money.

Supervisor Walt Abraham, whose district includes the plateau, declined to say how he will vote on the zoning change, although he said the idea of a county park at the site--which he calls “probably the most sensitive in the county”--is appealing.

Still, he added, “I come from a world of reality, and we’re not made of money. At this point, I don’t know what the answer is.”