Deep in a tawny canyon dotted by prickly pear, purple sage and green canopies of ancient oaks and walnuts, a rabbit scooted into the underbrush. Overhead, a great horned owl fluttered through treetops.
From a distant ridge came the sound of earth-moving equipment reshaping the land around a big house under construction amid a cluster of homes atop the canyon's western rim.
These are the two faces of Tonner Canyon, one of the last sizable chunks of undeveloped, privately owned land in the region. Its 6,500 acres--abundant in plants and wildlife, including rare and threatened species--are fast becoming an environmental battleground in a clash of open space versus development.
Los Angeles County in the mid-1970s designated Tonner Canyon a "Significant Ecological Area," a term that planners use to single out unusual private tracts of land that may face environmental difficulties from urbanization.
Now, as predicted, development pressures on Tonner Canyon indeed are coming to bear from many quarters:
* The Boy Scouts of America, which owns 3,700 acres in the canyon, is considering several options to develop part of the land.
* The Diamond Bar City Council gave tentative approval to developers to build 63 custom houses in a $90-million project, and applications for more projects are in the works.
* Developers have proposed a massive project for the southern end of Tonner Canyon in an unincorporated area of Orange County next to the city of Brea.
Complicating any comprehensive planning for the canyon is the jurisdictional latticework that overlies its eight-mile-long crescent shape. The canyon spans portions of three counties--Los Angeles, Orange and San Bernardino--and three cities--Brea, Chino Hills and Diamond Bar.
Diamond Bar and Brea each has plans to annex portions of the canyon and for planning purposes considers it a part of its "sphere of influence." And, the new city of Chino Hills took in a third of the canyon when it was incorporated in December.
In Diamond Bar, where the 2-year-old city of 53,000 has put the finishing touches on its first General Plan, developers and environmentalists have voiced sharply contrasting ideas about what should be done with the canyon.
"The whole issue is about destruction of our natural environment, just for the dollar," said Don Schad, an industrial electrical contractor who served on an advisory committee for the General Plan and who has hopes of creating a local nature conservancy to protect Diamond Bar's remaining undeveloped canyons.
Schad has been among the dozens who have staged marches through the city with placards saying "Save Tonner Canyon" and who have crowded into local meetings decrying the possible demise of what environmentalists call "Diamond Bar's rain forest."
Developer Daniel O. Buffington, a podiatrist who is a principle in a company planning the $90-million project--which falls entirely within the county-designated Significant Ecological Area--offered a dissenting view.
"First of all, you have to remember it is private property," Buffington said. Beyond that, he said, "that land has become too valuable to leave it in its natural state."
In its entirety that project on the city's eastern boundary would remove 800 native walnut trees. To compensate, developers would be required to plant 3,200 walnut trees.
As it gave tentative approval last month for the development that Buffington's company and one other developer plan for 87 acres, the Diamond Bar council held back granting a proposal for new houses on 73 more acres and required the developer to prepare an engineering study.
And on July 14, in spite of objections from a small group fearing that the city was not taking adequate precautions to protect Tonner Canyon, the council unanimously approved its General Plan, outlining a course of action for the next 20 years.
The plan advocates that the city should, "where ecologically feasible, maintain, protect and preserve biologically significant habitats," including Tonner Canyon.
Yet the plan acknowledges that development may be inevitable.
One of the projects that could most dramatically alter the canyon's environment is development of the Firestone Scout Reservation, which shut down in January as it coped with financial problems.
As a way to finance a new, scaled-down camp that would be built in a secluded 600-acre section of canyon woodlands, two Scout committees are considering potential residential or commercial developments for the reservation. A previous plan for a golf course fell through as the regional economy soured the Scouts' deal with a developer.
In explaining why the Scouts would even consider development, Scout spokesman Terry Tibor said: "The problem is the property has always been larger than we could use."
Straddling Orange and Los Angeles counties, the camp is just outside the Diamond Bar city limits but within the municipality's "sphere of influence."
Regardless of what happens at Firestone, Diamond Bar city officials hope to one day annex it. The General Plan lists the camp's zoning as "agricultural," but city officials said that could be changed if the Scouts develop a specific proposal.
In negotiating over any development at the camp, Diamond Bar Mayor Jay Kim said city officials face "a delicate situation." He said, "I'd like to leave (the canyon) the way it is . . . but we know that's not the reality."
Likewise, Orange County's Brea, a city of 32,000, is eyeing annexation of the canyon's southern end, where a Laguna Hills developer and three oil companies propose to build as many as 2,000 homes and a business and commercial district in a 7.4-square-mile area. One-eighth of the area includes 500-plus acres of Tonner Canyon near the Orange Freeway.
A itizens commitdailyas completed a report on concerns about the project, which would increase Brea's lmed area by 70% if it were annexed.
Community membtod studying that area "discovered that it's not as pristine" as they had thought, said Jimmoutts, director of Brea's development services, who noted that oil companies have maintained wmels for a century in Tonner's southern end.
Still, he saidb officials realize the canyon's ecological importance and hope "to strike some kind of balance" between the ecology and development.
Soon, Cutts said, developers will begin environmental studies on the canyon.
Diamond Bar Planning Commission chairman Bruce Flamenbam said he would welcome studies on Tonner because "I just don't think we know enough about it."
Previous research has concluded that the canyon is ecologically significant for its diversity in native plants and animals, and for its unusual expanse of relatively undisturbed habitat, which once was commonplace.
Its stands of native oaks and walnut trees were among the reasons that Los Angeles county planners singled out the canyon.
According to Jack Bath, a Cal Poly Pomona biological sciences professor, the canyon has at least a dozen rare plants, including three extremely rare varieties possibly facing extinction: Braunton's Milk-vetch, heart-leaved Pitcher sage and the many-stemmed Live-forever.
In addition, Bath said the canyon is a major pathway for cougars, whose local habitat is dwindling.
Development in the canyon, especially on the scale planned in Brea, he said, could wipe out the cougars and set off a chain-reaction. Cougars, he said, would no longer be present to eat the deer, which would proliferate; an increased deer population could then overgraze native plants and herbs to extinction.
To further thicken the plot, the entire length of Tonner has been proposed as the location for a roadway or perhaps a monorail that might help ease increasingly severe traffic problems on the Pomona and Orange freeways, and on Grand Avenue and Carbon Canyon Road.
In its recently adopted General Plan, Diamond Bar left open the possibility of a transportation corridor. The development of a road is favored by many officials in surrounding communities, but it is opposed by others who say it would be an environmental disaster.
In addition, since December, part of Tonner Canyon has fallen within the domain of a new governmental entity. Chino Hills, with a population of 46,500 that is expected to double over the next several years, encompasses most of the canyon's northern third. The city is just beginning to develop its General Plan, which will include Tonner--on the western edge of one of the fastest-growing areas in the nation, Riverside and San Bernardino counties.
Worried about transportation issues as well as environmental ones, Chino Hills Mayor Gwenn Norton-Perry considers it a significant problem that no existing regional body supervises planning for Tonner Canyon. "It's called regional cooperation," she said, "and cities don't know how to do that."
But she said that she is hopeful that government officials can somehow devise a way to plan comprehensively for the canyon.
Flamenbam of Diamond Bar's planning commission said he too is worried that the three counties and three cities will be unwilling to look at the canyon as a whole.
As it now stands, he said, with no single agency in charge, Diamond Bar would be hard-pressed to have much say even "if Brea wants to put a lead smelter in the canyon."
Open Space vs. Development Tonner Canyon, which contains one of the last large undeveloped chunks of privately owned land in Los Angeles County, is abundant in wildlife and plant life, including large stands of oaks and California walnuts. Los Angeles County has designated most of its portion of the canyon as a "Significant Ecological Area." But development pressure bears down. Much of the canyon is owned by the Boy Scouts of America, which has closed its Firestone Scout Reservation and is considering development. In addition, houses are creeping over the west canyon rim from Diamond Bar. The canyon's alignment across three counties and three cities complicates efforts to protect it.