Aggressive land acquisition and development controls are needed to save what’s left of a wildlife corridor that sustains bobcats, mountain lions, badgers and other wildlife in the Santa Monica and Santa Susana mountains and the Simi Hills, according to a new report.
Animals need large, connected habitat blocks that allow them to move freely within the three ranges to colonize new territories and avoid the inbreeding that leaves them genetically weakened and susceptible to disease, according to the report financed by the Santa Monica Mountains Conservancy.
Several large blocks are already under permanent protection, including Malibu Creek and Topanga state parks, and Cheeseboro Canyon and Sage Ranch in the Simi Hills.
But roads and private developments have “virtually severed” the connections between these preserves, according to the report, and threaten to permanently split the corridor.
“The consequences of the permanent isolation of any one of these three ranges include the probable extirpation of mountain lions, badgers, gray fox, bobcats, mule deer, long-tailed weasels and possibly coyotes over the next 50-200 years,” the report says.
The 92-page report is the first to identify key links in the corridor, focusing on areas of the Simi Hills that form a bridge between the Santa Monicas and Santa Susanas. It identifies specific parcels to be protected by acquisition or easements at a cost in the millions of dollars. And it recommends construction of two new tunnels under the Ventura Freeway in Agoura to provide for wildlife movement.
The report also suggests development curbs within the wildlife corridor, including requirements that:
* Wildlife crossing structures be incorporated in new road and road improvement projects.
* Buildings in new developments be clustered rather than dispersed to reduce habitat intrusions.
* Developers compensate for destruction of woodland, wetland or stream-side habitats by preserving at least twice as much prime habitat elsewhere in the corridor.
* “Teams of local ecologists” be actively involved in decisions on location of development and habitat dedications.
These steps, the report says, “will require the active, coordinated and cooperative support of a multiplicity of agencies and governing bodies” that now have no policies to protect the corridor.
The report’s author, biologist Paul Edelman, said these officials have not yet seen the report nor have discussions begun on implementing its recommendations.
The report was supervised by the Nature Conservancy, a nationally prominent conservation group that became involved at the request of the Santa Monica Mountains Conservancy, a state parks agency that buys land in the Santa Monicas and other mountains and hills ringing the San Fernando Valley.
The Nature Conservancy agreed to manage the study to assure that it was “accurate and biologically sound,” said Sally Smith, director of communications for the Nature Conservancy in San Francisco.
An independent consultant when the Nature Conservancy retained him for the study in 1989, Edelman has since joined the staff of the mountains conservancy.
Edelman said the study demonstrated that animals will use man-made structures to cross freeways, a finding he believes supports the need for the Ventura Freeway tunnels.
According to the report, the Rocky Peak fire road overpass and an equestrian tunnel near the Santa Susana Pass provide good connections across the Simi Valley Freeway between habitat areas to the north and south.
As part of the study, Edelman and a colleague made 52 weekly visits to the equestrian tunnel during 1989-90 to observe tracks of animals crossing to the north and south. They noted 52 crossings by mule deer, 42 by bobcats, 85 by coyotes, 12 by raccoons, 9 by gray foxes, 10 by skunks, 4 by ring-tailed cats and 4 “possible” crossings by mountain lions. Often prints were too indistinct to identify and, at the most, the tracking data represents 40% of total crossings, Edelman said.
Some creatures took their chances on the Simi Valley Freeway despite the equestrian tunnel. A mature mountain lion was struck and killed on the freeway in November, 1989, and a badger was killed in June, the report said.
Along the Ventura Freeway, the best wildlife crossing--the Liberty Canyon Road underpass--is unsatisfactory because of development hugging the southern side of the freeway.
From 1985-89, 52 mule deer, 6 bobcats, 74 coyotes and 5 gray foxes were killed on a stretch of the freeway in Agoura, according to data cited in the report.
The report calls for construction of wildlife tunnels beneath the Ventura Freeway west of Liberty Canyon and at Crummer Canyon. It warns, however, that the linkage provided by these tunnels could be severed by proposed developments on both sides of the freeway.
In some ways, the study paints a gloomy picture of the corridor’s future, which depends on vast sums of acquisition money and unprecedented cooperation among land-use and highway agencies and developers. Even if most of the pieces fall into place, a mere handful of highway and development projects, strategically placed, could permanently sever key connections in the corridor.
According to an estimate by the mountains conservancy not contained in the report, about 15,000 acres in the three ranges, valued at about $73 million, should be acquired or preserved by easements to protect the wildlife.
By contrast, the conservancy is assured of only $42 million over the next 10 years to buy land and cannot spend all of it on the wildlife corridor. These are remaining funds from state park bond issues. More money could come from the Legislature or future bond issues.
While acknowledging the obstacles, Edelman said conservationists must fight to preserve the corridor. “You’ve got to at least try,” he said. “There’s so much at stake.”
Just knowing that wild animals prowl the urban fringe provides “a certain sense of comfort,” Edelman said. “I think people’s frame of mind is improved by living in close proximity to nature,” he said.