Wildlife bridge touted for I-15

By: DAVE DOWNEY - Staff Writer | Saturday, April 9, 2005 10:55 PM PDT ∞

TEMECULA ---- The oak-and-chaparral skin of the rugged mountains on the Riverside-San Diego county line covers a solid granite core, making the spot ideal for a rock mine, proponents of a quarry say.

However, biologists say the same spot is the best remaining location for building a landscaped bridge over Interstate 15 to provide a way for wildlife ---- cougars in particular ---- to travel safely between the largely isolated Santa Ana Mountains on the west and Palomar Mountain to the east. The Santa Anas are the mountains of the Cleveland National Forest between Temecula and Corona.

Scientists hope to have such a bridge in place south of Temecula by 2010.

Indeed, the county line is one of 15 sites targeted by biologists in a regional campaign to maintain or re-establish connections between urban Southern California's rapidly shrinking islands of natural habitat. Other sites are along Interstate 10 between the San Bernardino Mountains and Idyllwild's San Jacinto range, and I-15, which divides the San Bernardinos from the San Gabriel Mountains.

Such connections are crucial, biologists say, if Southern California is going to keep its rich diversity of wildlife.

That diversity is greater in fact than most other areas of the United States because of the region's widely varying topography and climate, which are influenced by the dramatic convergence of dusty deserts, lofty mountains and the Pacific Ocean, scientists say. Yet, more than 400 species of plants and animals in that rich repository of life are at risk of extinction because of the region's relentless urban advance, according to a group of biologists that completed a regional plan for wildlife connections in May 2004.

One of the most threatened animals of the Santa Anas is the cougar, which requires a large territory and is being squeezed on all sides by encroaching suburban development. Experts estimate that fewer than 20 cougars remain in the mountains. And with humans pushing deeper into the lower canyons leading into the range, mountain lion sightings are on the rise.

On a recent tour of a 311-acre site northwest of I-15 and Rainbow Valley Boulevard near Temecula that a $2-billion-a-year California firm is targeting for a mammoth quarry, a company official noted there is development in the area now, including nurseries and the U.S. Border Patrol checkpoint station. Gary Johnson, a manager for Granite Construction Co. in Indio, said it would seem there already are major barriers to wildlife movement.

"I think everybody needs to realize that right now there is no linkage," Johnson said.

Paul Beier, Northern Arizona University professor of conservation biology and wildlife ecology, and co-author of the regional plan, acknowledged that conditions at the proposed bridge site are less than perfect.

"It's obviously not ideal," Beier said, in a telephone interview last week. "We could have designed a much better linkage if we had done this 20 years ago. But that is no reason to give up. We have to work with what we've got, and we can make this work."

Success elsewhere

There is enough open country for animals to travel through ---- once they get beyond the busy eight-lane freeway, he said. And scientists are sure animals would use a bridge over the highway because they have documented cases where mountain lions crossed, even though that meant dodging cars traveling 80 mph.

At least four cougars died trying to cross between the Santa Margarita River and U.S. Border Patrol station in the early 1990s, said Beier, who has studied the mountain lions of the Santa Anas extensively.

"The mountain lions are telling us that that is the place where they want to cross," he said.

Because the freeway was laid across a deep cut in the shoulder of the mountains, a wildlife tunnel under the freeway probably would not work there, Beier said. He said a bridge over I-15 that follows natural contours of the land would be more useful.

Claudia Luke, biologist and director for the nearby Santa Margarita Ecological Reserve operated by San Diego State University, said a regional coalition of scientists is proposing to build, within the next five years, an overpass to help animals travel across I-15. No cost estimates were available.

Biologists aren't talking about a bare concrete bridge, Luke said. Rather, she said they are thinking of a structure roughly 100 feet wide, covered with dirt, native chaparral plants and possibly even small trees.

"You're making a continuous habitat walkway over the highway," Luke said. "For many species, that is very important because they don't like going out in the open. It's true a lot of people don't know about these, but they are becoming more widespread in the United States and in Europe and in Australia."

And they work, Beier said.

For proof, he pointed to the Coal Canyon interchange on Highway 91 near Corona. It was abandoned in November 2000 to make a way for cougars to travel safely across the 12-lane freeway between the Santa Ana Mountains and Chino Hills. Because of signals picked up by radio collars, pictures taken by remotely controlled cameras and tracks left behind, scientists say they know that cougars, bobcats and other animals are traveling through a tunnel that was once filled with cars.

"It was an accident, basically," Beier said. "We didn't design it for wildlife, but they used it anyway. Even before we converted that vehicle underpass into a wildlife crossing, it worked. Radio-tagged animals used it quite regularly."

The state blocked the interchange's offramps after a developer axed plans for 1,500 homes in the scenic canyon to the south. The state bought the 649-acre site and brought it into the state park system. The state later ripped out the asphalt road through the underpass, leaving behind a barren dirt path for wildlife to walk on. Chino Hills State Park workers are preparing to plant bushes and trees.

A road for animals

Other wildlife bridges and tunnels have proven successful along Highway 260 in the Arizona mountains, on Interstate 75 through the Florida Everglades and across the TransCanadian Highway in the Canadian Rockies, Beier said, although they work best in conjunction with fences that guide animals to crossings. He said Florida is an example of how crossings can work in heavily urbanized regions.

"That used to be a place where animals were killed all the time. Bears, alligators and pumas were routinely run over," he said. Not anymore.

In Southern California, Beier said, just a handful of fatalities along I-15 could spell the end of the cougar in the Santa Anas. He estimated there are no more than a dozen adult females and four or five adult males in the western Riverside County range, leaving the population in a precarious position.

"Accidents can happen when you have small populations," he said. "If two adults males get run over and one gets shot for eating sheep, then you're down to one adult male."

And because the Santa Ana range is small, it cannot support a larger population, Beier said. Only with a connection to other protected natural areas can the cougar survive there in the long run, he said.

While much emphasis on the need for such connections is placed at the swift feet of cougars, Alissa Ing, resource ecologist for the Inland Empire district of state parks, said links between ranges are important for smaller animals, too.

"It's just as important for frogs and snakes and insects," Ing said.

It is even important for plants, she said.

The bottom line, said Luke, is people, plants, big animals and little ones all need to travel.

"Everything needs to be able to move," Luke said. "It's just that our movements shut off their movements. And we're just trying to say, 'Here's your road.'"

Contact staff writer Dave Downey at (951) 676-4315, Ext. 2616, or ddowney@californian.com.

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