Fires take toll on San Diego’s wildlife

  • The Thorne's butterfly, lost its entire known habitat in the fires that struck Southern California last fall

    DOUGLAS AGUILLARD
  • The blackened hills of Otay Mountain

    MICHAEL KLEIN
 

Rare butterfly is likely extinct, while imperiled gnatcatcher loses a chunk of habitat

The fires that blackened 775,000 acres and 2,400 homes in Southern California this October also devastated plant and animal populations in San Diego County, one of the most biologically diverse places in the United States, and home of the country’s first multiple-species habitat conservation plan (HCN, 11/10/03: San Diego's Habitat Triage).

No other species has been left in as precarious a position as the Thorne’s hairstreak, a tiny butterfly that is brownish in color until the sun gives it a purplish-green iridescence. It was only discovered by scientists in 1972, and it lives only on 3,500-foot Otay Mountain on the U.S.-Mexican border. The butterfly’s population has varied yearly, but stood at a few hundred at most before the fires.

On Oct. 31, a few days after the fires peaked, biologist Michael Klein saw firsthand the consequences for the Thorne’s hairstreak. Venturing up the north side of Otay Mountain, about 15 miles southeast of downtown San Diego, he came across a series of blackened hills. The Tecate cypress trees, which host the butterfly and grow in only two other places in Southern California and northern Baja California, had been reduced to stumps, he says.

“There may be an isolated area that survived, but all the known locations in the entire world where we had reported the butterfly, all six locations on Otay Mountain, all burned,” says Klein, who runs a biological consulting firm that surveys wildlife for land developers. Even if the cypresses regenerate quickly, the butterfly’s caterpillars generally won’t start eating them until they are 25 to 30 years old. “(The butterfly) is one that has potential to go extinct. It’s a high probability,” says Klein.

“Emotionally, it’s distressing,” he adds. “It’s not one of those species that in my lifetime I ever expected to see it potentially go extinct.”

Scientists probably won’t be able to draw firm conclusions about the fires’ effects on the butterflies and other wildlife until next spring at the earliest, says Jane Hendron, a U.S. Fish and Wildlife Service spokesperson.

But preliminary findings show that two other butterfly species, the Hermes copper and the endangered Quino checkerspot, were also seriously damaged. It’s likely that thousands of butterflies were destroyed. The fires also torched much of the coastal sage scrub that plays host to the threatened California gnatcatcher, the poster child for the 1997 Multiple Species Conservation Program (MSCP).

As the smoke clears, environmentalists say the fires have confirmed their doubts about whether the program protected enough land to accomplish its goal to save 85 imperiled animal and plant species in the midst of Southern California’s runaway urban sprawl.

Gnatcatcher could be in trouble

Early reports portray the fire as an equal-opportunity destroyer across San Diego County. Overall, it burned about 390,000 acres in the county — nearly 15 percent of the county’s total land area — according to a mid-November report from a team of scientists investigating the damages. “The state has never seen a loss of this magnitude,” the report says.

The report found that the fire damaged 13 complexes of vernal pools — small, seasonal wetlands that fill with water during and after the winter rainy season and play host to as many as seven federally protected plant and animal species.

Many of the region’s plants and animals have co-evolved with fire and are adapted to it, sometimes recovering swiftly in the months and years after the headlines die down. But historically, fires occurred far less often than they do now. A century of fire suppression, years of drought and other factors have turned San Diego’s forests into tinderboxes, says the service’s Hendron.

The Tecate cypress, for instance, can survive fires every 40 years. But fires are now occurring every 20 years, about the time that the trees reach reproductive age, which raising concerns about how well the species will recover.

While some patches of green have already reappeared in the region’s wildlands, those wildlife species that depend on the recovering vegetation may face a tough road ahead. Inside the county, the blaze destroyed 71,000 acres, or 30.9 percent of the coastal sage scrub that plays host to the threatened California gnatcatcher, according to statistics kept by the nonprofit San Diego Recovery Network, a group consisting of scientists and environmentalists.

The loss of habitat — combined with the exotic West Nile virus, which arrived in the county in fall 2003 (see story page 4) — is expected to seriously affect the birds next year, according to the scientists’ report: “The combination of West Nile virus and reduction in population as a result of the fire may be a major impact to the California gnatcatcher.”

The report also says that emergency Endangered Species Act listings may be warranted for the Hermes copper butterfly, which lost 90 percent of its habitat, as well as the Thorne’s hairstreak — if any remain.

Conservation plan called into question

The fires’ implications for the habitat conservation plan also remain unclear.

David Hogan of the Center for Biological Diversity says that because of the fires, his group is considering asking the Fish and Wildlife Service to revisit its conclusions from 1997 that the conservation plan adequately protected the Thorne’s and Hermes butterflies and the Tecate cypress, and possibly the gnatcatcher.

“The lesson learned from the fires is that the MSCP is too small and fragmented, and that too much of the preserve can be lost in one fire event,” says Hogan, whose group has criticized the conservation plan for many years.

The service’s Hendron says it’s too early to make such judgments; the true test will come when the various species of birds and butterflies enter their breeding seasons and the plants begin to recover. Says Hendron, “These are all the types of things that are going to take a little bit of time.”

The author lives in Tucson, Arizona, where he reports for the Arizona Daily Star.

U.S. Fish and Wildlife Service Jane Hendron, Carlsbad office, 760-431-9440, ext. 205
Anne Fege chair, San Diego Fire Recovery Network and supervisor, Cleveland National Forest, 858-674-2982
Michael Klein butterfly specialist, 619-282-8687