Human activity in the wildlife corridor connecting Laguna Coast Wilderness Park and the Cleveland National Forest is impeding the movement of animals along the 6-mile stretch, according to a recent study by Laguna Greenbelt Inc.
The study examined the corridor between the foothills of the Santa Ana Mountains and 22,000 acres of protected coastal land.
Orange County Great Park developer FivePoint Holdings broke ground in 2018 on a project to restore 2½ miles of the corridor in Irvine to help native animals safely pass through densely populated areas without human interference. The company did not respond to requests for comment about its eventual completion.
Organizers of the study said it was done to examine how well the corridor functions and to identify possible improvements. The data pointed out challenges at “pinch points” where human activity is heavily documented, they said.
The existing corridor is a series of open areas devoted to agriculture and water conveyance and is bisected by major roadways such as the 5 and 405 freeway interchange, Irvine Boulevard, Research Drive and Irvine Center Drive.
Twenty-one cameras were set up at 11 sites between late 2016 and late 2018 for photographs and recordings of animals as they passed through day and night. Volunteers reviewed hundreds of thousands of photos, said Mary Fegraus, a longtime environmentalist with Laguna Greenbelt.
The photos and videos were categorized by biologists at the San Diego Natural History Museum, who compiled the report.
“During the camera study, we were looking at the undercrossings ... and we found they weren’t all functional, including the biggest culvert under the I-5,” said Elisabeth Brown, a biologist and president of Laguna Greenbelt.
“There are few, if any, alternatives for the animals. If the animals refuse to go through the existing culvert, then we may need a bridge similar to the Liberty Canyon project in [Los Angeles] County,” Brown said. “Even though that project is targeted to [mountain] lions, the problems are the same for our target animals — bobcats, coyotes — here.”
Though underpasses available beneath the roadways facilitate the movement of some animals, many medium-size and large mammals are less likely to approach them — especially in sections away from preserved land, according to the study. One of the most significant issues preventing some animals from using the underpasses may be human presence at the sites.
Other recent studies in Orange County have found strong evidence that wildlife will retreat when encountering humans, said Megan Lulow, director of operations for the UC Irvine Natural Reserve System.
"[Wildlife are] afraid of humans and are intimidated by them, so they’ll just avoid them,” Lulow said. “It’s relative risk ... particularly if you’re talking about the culverts or the corridors themselves. That’s a restricted space. If they sense there are humans there — which is a threat — they’re going to be less inclined to go into a restricted space.
“They might be on their way to cross a trail, but then they’ll have to move back and wait. It affects their overall energy budget and then it becomes a really significant problem when they can’t get to where they’re going at all if it’s a restricted area like a culvert or corridor.”
If wildlife can’t pass through the corridor, Lulow said, it could lead to reduced resources and eventually to inbreeding depression, in which recessive and possibly harmful genes become more prominent due to a lack of genetic diversity in the population.
The report offered several suggestions on how to improve the corridor as it continues to develop, such as planting dense vegetation along the path, limiting light pollution for nocturnal animals, installing fencing and possibly “critter shelves” — elevated metal grates attached to the upper parts of a culvert to be used as a path to avoid predators, thick mud or standing water — or tubes for smaller mammals.
“Laguna Greenbelt is not a landowner and so they need to convince landowners and other partners ... that we need to figure out how to make this work,” Fegraus said.
“Now with this data really verifying some of the thoughts, we’re ready to take the next step,” she said. “Something has to be done. Not in the next 10 years but as soon as possible.”