Survey Lists 300 Pathways as Vital to State Wildlife

The bobcat’s paw prints in the Santa Margarita Ecological Reserve pointed east toward the Palomar Mountains, a good place for bobcats, if only this one can make it there safely.

But to get there, the cat must cross eight lanes of Interstate 15 near fast-growing Temecula, and busy interstate highways are one of the reasons wild animals can no longer move readily from one familiar habitat to another. Increasingly cut off and confined, dozens of species across California are doomed to extinction, scientists fear, unless people can clear blocked corridors and preserve open ones.

Now, a team of biologists representing the state and several conservation groups has identified more than 300 natural pathways throughout California thought to be vital to the survival of dozens of wildlife species.

Their survey of wildlife corridors is a key step in an ambitious process that ultimately could lead to preserving or restoring many of the pathways. Scientists hope to forge a network of such links to allow animals to move back and forth across parks, wildlife preserves and other wild lands in the nation’s most populous state.

Many of the links would function as land bridges across developed areas. A big part of the challenge ahead is buying the land or acquiring necessary rights of way.

Without action now, however, many linkages will be severed, turning wildlife refuges and other chunks of wilderness into fragmented islands in a sea of development, predicts a report released Monday by five public agencies and nonprofit groups. Island habitats long have been known as hotbeds of extinction, where wildlife are highly susceptible to inbreeding and disease.

The danger looms large in California, which has more federally endangered and threatened species than any other state but Hawaii.

“The risk is, if we don’t think about issues of linkages and connectivity, we just end up protecting islands that lose their health over the long term,” said Graham Chisholm, executive director of the Nature Conservancy of California, which helped spearhead the survey. The nonprofit organization is best known for its worldwide acquisitions of wildlife habitat.

“In order to have healthy, vibrant sites with a full array of representative species, we need to think of how the site remains connected to larger landscapes,” Chisholm said.

Although wildlife biologists have been mapping corridors for years, the new survey stands out because it brought together 160 experts from public agencies, advocacy groups, consulting firms and academia.

Linkage Preservation Is Discussed

The survey represents a maturing of a scientific theory once thought of as novel. Now, even state parks officials are embracing the notion of linkage preservation as they debate what lands to purchase.

“To me, it’s the most important thing we can do to preserve values on parks lands today,” said Richard G. Rayburn, chief of natural resources at the state Department of Parks and Recreation. He recalled the warning of Harvard University professor emeritus E.O. Wilson several years ago about the problem of fragmented landscapes: that unless society moves quickly, it would be left with “pathetic remnants” of wild lands.

“That really hit home to me when I thought about places like Chino Hills, the Verdugo Hills, the Santa Monicas,” Rayburn said. “You can’t wait around much longer.”

The state Parks Department collaborated in the new report, along with the Nature Conservancy, the California Wilderness Coalition, the Biological Resources Division of the U.S. Geological Survey, and the Center for Reproduction of Endangered Species of the Zoological Society of San Diego.

The project stemmed from an April 1999 workshop at the UC Riverside James Reserve near Idyllwild, organized by the California Wilderness Coalition. There, scientists mapped corridors in Southern California and promised to continue their efforts statewide.

That next step came in November, when all of the experts met in San Diego to identify linkages throughout the state and attempted to rank their importance.

The proceedings have been assembled in the report “Missing Linkages,” written by Kristeen Penrod, executive director of the South Coast Wildlands Project. Penrod’s group is part of an effort across North America to preserve wildlife corridors.

“This is definitely the first critical step in putting this on the agenda of a statewide campaign to go forward with preservation and restoration,” Penrod said. She is helping plan an Aug. 17 workshop where experts will decide on 10 or more top-ranked linkages in the coastal region of Southern California.

One place sure to make that list is the so-called Pechanga corridor, which once tied the Santa Ana range to the Palomar Mountains in the Temecula area. Today, Interstate 15 cuts directly across that corridor, flanked by a fast-growing panorama of homes, malls and office parks.

Experts worry that unless that corridor can be restored, wildlife will suffer in the nearby Santa Margarita Ecological Reserve, site of a San Diego State University field research station. In fact, the Pechanga corridor could be crucial in preventing the entire Santa Ana range from becoming an island, said Sedra S.L. Shapiro of the university’s field station programs.

Large mammals still move through the reserve and its idyllic, shaded canyon cradling the far upper reaches of the Santa Margarita River. The bobcat whose paw prints were visible last weekend is one of those mammals. One way for animals to get past obstacles such as Interstate 15 is to create a wildlife bridge across the freeway, much like one that scientists have studied in Luxembourg. That bridge is topped by three feet of soil, grass and trees, allowing deer, boar and other creatures to pass undeterred over traffic, said Hartmut Walter, a zoologist and UCLA geography professor.

But Some Question Importance of Corridors

The confidence that linkages will save species is not universally shared.

Some scientists have questioned the importance of corridors, saying they can serve as vectors for disease and predators.

The state nonetheless has begun to purchase land for corridors.

One recent acquisition is Coal Canyon in Orange County, which connects Chino Hills State Park to the Cleveland National Forest.

Without the link, wildlife would have suffered severely in the Chino Hills and other preserved land to the north, said Claire Schlotterbeck, president of Hills for Everyone, the group that created Chino Hills State Park and lobbied for preservation of Coal Canyon.

“Those areas would have become isolated. All of the land we fought for north of the 91 would have become at risk for a precipitous local extinction rate of 50% or more,” she said. For example, if the park’s mountain lion population declined from inbreeding, the numbers of opossums, raccoons and skunks would have soared, feeding on the eggs of native birds.

Caltrans officials are now talking of removing the Coal Canyon onramps and offramps to the Riverside Freeway for both environmental and traffic safety reasons, Schlotterbeck and Rayburn said.

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Times staff writer Seema Mehta contributed to this story.

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Wildlife Corridors

Scientists have pinpointed more than 300 corridors traditionally used by animals to move between reserves, parks and other natural areas across California. Experts fear that as new homes and highways sever corridors, wild areas will become fragmented islands in an urban sea, speeding the extinction of native wildlife.

Source: Map data courtesy of Rich Hunter, Talon Associates

The entire report is on the Web at: www.calwild.org/pubs/reports/linkages/index.htm