Many Rare Birds Perished in Blazes, Biologists Report : Endangered species: About 15% of surviving gnatcatchers died, as did up to 20% of cactus wrens. Remaining habitat is scarce, and development rules could stiffen.

In a grim assessment of last week’s raging wildfires, federal biologists have reported to Interior Secretary Bruce Babbitt that a large percentage of Southern California’s rare birds perished, mainly in Orange County, when 170,000 acres of sage and chaparral were reduced to piles of gray ash.

Approximately 15% of the last surviving California gnatcatchers were apparently wiped out, or about 330 pairs in three counties, according to a preliminary briefing that U.S. Fish and Wildlife Service biologists prepared for Babbitt before new wildfires broke out Tuesday in the Southland. The tiny gray songbird, which depends on sagebrush for its survival, was declared a threatened species by the federal government in March.

Also killed were an estimated 460 pairs of cactus wrens, 15% to 20% of the U.S. population of the rare species, which live in patches of prickly pear cactus in sage-lined hills and are under consideration for federal protection.

The firestorms have opened a disturbing new chapter in the years-long struggle to save Southern California’s vanishing coastal sage scrub from development without derailing economic growth.

Just seven months ago, Babbitt announced that the mix of arid shrubs is the centerpiece of a new national experiment to use the Endangered Species Act as a preventive tool to save rare wildlife yet avoid its usual economic gridlock. The idea behind the California Resources Agency’s program is to let developers voluntarily create preserves using scientific guidelines while letting the rest of their land undergo development without long delays.

The innovative conservation program is expected to remain intact, but the planning of the preserves may have to undergo considerable changes because of the fires. Thousands of acres of prime habitat in Orange, San Diego and Riverside counties were rendered useless to wildlife--at least for the five to seven years it takes for the habitat to revive, biologists said.

“We have had an experience here that can only be called catastrophic,” said Dennis Murphy, a Stanford University biologist who heads a scientific review panel for the state’s coastal sage scrub planning program.

“This is not the standard late-autumn sequence of fires. This was a substantial environmental emergency,” Murphy said. “I’m ready to be sickened when I see the total numbers” of acres damaged and birds destroyed, he said.

The U.S. Fish and Wildlife Service and the state Resources Agency are trying to decide whether to bolster protection of remaining sage scrub in Orange, Riverside and San Diego counties. Even Orange County’s controversial San Joaquin Hills tollway, which had already been approved by the federal wildlife agency, may face more environmental hurdles before the scrub can be graded.

“It certainly appears that we are going to have to look with a very critical eye at development proposals, particularly in coastal Orange County,” Murphy said. “The carrying capacity of coastal Orange County for the gnatcatcher has been diminished and probably will stay diminished for five or more years.”

Officials warn that the death toll in the report is preliminary, since more precise assessments cannot be made until Murphy, two other scientists and federal officials fly over the fire-scarred land to assess the damage in the next few days. The estimates were compiled by federal biologists who compared counts of birds made last spring with a general outline of the acreage that burned.

“Until we know precisely how bad a hit the gnatcatcher took with all this, we won’t know what is needed. But (the fires) definitely change the rules of the game,” said Fred Roberts, a Fish and Wildlife Service botanist based in Carlsbad.

California Resources Secretary Douglas Wheeler, who has flown over some the burned areas, said Tuesday that he was “astounded at the loss of the natural areas across the range of the fires.” But he cautioned that the ecological assessments are early, with some land still ablaze, so the impact on the conservation program remains uncertain.

Fire is common in sage scrub, and in the long run it can be beneficial, but conservation officials worry about the short-term impact on the rare birds over the next few years.

“No question the loss of any habitat is critical at this point, but to say more than that is premature,” Wheeler said. “It is clear that what habitat remains is now more valuable (to conserve) than what it was a few days ago.”

Wheeler said the fire is “bound to have some effects” on the preserve planning, especially for the Irvine Co., Orange County’s largest private landowner, which suffered the largest loss of acreage of any developer. The company was well on its way to identifying which land to conserve, but the fires burned about 4,000 acres of land north of Laguna Beach that was intended to be the heart of its preserves.

The fires probably killed about 200 pairs of gnatcatchers in Orange County, or nearly 30% of the county’s total, and 100 pairs in Riverside County, or 40% of the total there, the biologists’ report says. San Diego County lost at least 30 pairs in one area. Before the fires, 2,500 pairs of gnatcatchers existed, according to counts last spring.

Cactus wrens, which had numbered about 3,000 pairs before the fires, experienced an even more severe blow, according to the briefing. About 370 pairs were wiped out in Orange County, or 15% of the county’s total, and Riverside County lost nearly all of the species, or about 90 pairs.

The Fish and Wildlife Service is expected to decide within a few months whether to protect cactus wrens as a threatened or endangered species.

Wildlife biologists say some of the gnatcatchers and wrens in the burned brush may have survived. But they suspect that most could not escape because such massive areas burned and housing developments in the fire areas left them few places to retreat.

“When the fire rushes down one ridge, the gnatcatchers move over, but then that ridge went up in flames too. Eventually they probably didn’t have anyplace to go,” Roberts said. “You might have some scattered around in the housing areas, but when they come back to feed, there’s nothing there.”

The report to Babbitt noted that “highly significant areas with high-quality wildlife habitat have burned,” with the most severe losses, about 16,000 acres of scrub, in the San Joaquin Hills between Laguna Beach and Newport Beach.

In addition, Riverside County lost an estimated 6,200 acres of sage scrub to fires, or 8.2% of the county’s total, and 20,000 acres burned in San Diego County.

Earlier this year, Murphy’s panel of scientists determined that no more than 5% of existing coastal sage scrub could be developed over the next five years without permanently hurting the chances of the species’ recovery.

But in just 24 hours, the fires wiped out perhaps three times more scrub than the scientists had deemed acceptable. Murphy said he believes the birds can eventually bounce back, but only if the burned land is allowed to revegetate.

Wheeler said the state Resources Agency is ensuring that fire officials will use plants that are native to the area when they reseed fire-damaged hills to prevent slides and erosion.

Southern California developers, who stress that fire is a natural element of the birds’ arid ecosystem, worry that the federal and state agencies may overreact.

“The habitat is still there--no one paved it, no one built houses on it. It still exists. It just is going through a transition and it will heal itself,” said Laer Pearce, a spokesman for a coalition of Orange and San Diego county developers involved in the state’s conservation-planning project.

“It’s a real shame that it happened, but there is still contiguous occupied habitat and the seeds will come up in the spring and the birds will repopulate these areas very nicely,” he said.

The conservation program was specially created for Southern California because a large amount of the land inhabited by gnatcatchers is prime, privately owned real estate worth millions of dollars.