Octa's transportation blog

Restoring Orange County’s Native Habitat

Photo Credit: ERIKA TAYLOR, Voice of OC.

This article originally appeared in Voice of OC

Orange County’s open space has shrunk in past decades with the expansion of cities, freeways and infrastructure. Environmental impacts such as wildfires, overgrazing and invasive plant species have also damaged what open land is left.

“There is not a whole lot of Orange County’s natural landscape left,” said Leslie Hill, Environmental Mitigation Program Manager at OCTA. “We need to try and protect what we have left.”

Orange County contains more than 30,000 acres of open space lands, according to the Irvine Ranch Conservancy. Over nearly a decade, the Irvine Ranch Conservancy has focused on mitigating these impacts in two ecologically sensitive areas: Agua Chinon and Silverado Canyon.

“There are a lot of open space lands here in Southern California that have been set aside by states, cities, and OC Parks, but some of them are in terrible condition,” said Robert Freese, Program Manager for Habitat Restoration and Enhancement at the Conservancy. “We want to bring it back to the way it looked 300 or 400 years ago, before the impacts,” he said. 

Both projects were sponsored by Orange County Transportation Authority (OCTA) with funding from the Renewed Measure M Freeway Environmental Mitigation Program. 

Measure M is a sales tax that funds improvements in freeways, streets and the transportation system in Orange County. More than 350 acres of habitat restoration has been funded by the agency, over a total of twelve restoration projects, according to Marissa Espino, Public Outreach Section Manager at OCTA. Orange County contains more than 7,000 acres of open space lands.

The Lower Silverado Canyon project received just over $1 million in funding. Agua Chinon was included in a joint project with Bee Flat Canyon, which received over $1.5 million in funding for restoration, according to Hill.

Agua Chinon

The 6.1 acre Agua Chinon restoration project prioritized the cultivation of native plants, and ultimately the eradication of invasive species. As a riparian, or creekside, habitat, its vegetation is especially important to surrounding habitats, according to Freese.

Agua Chinon begins in a geological landmark known as The Sinks, a natural sandstone formation within Limestone Canyon. The wash then crosses under the 241 toll road, eventually joining San Diego Creek and Newport Back Bay.

“When we started in 2013, we did baseline surveys to assess the condition and the proportion of needed vegetation, versus how much non-native vegetation and use that to determine what is reasonably accomplishable,” said Freese. “It was a weed-filled valley.”

After depleting these weeds, they planted wildflowers and other native plants, such as mule fat, which grew slowly at first due to the dry soil.The project was nearly complete in 2020, after years of monitoring the health of the native plants and eradicating invasive weeds.

In October 2020, a fire swept through the wash. “It was a severe burn, and all our vegetation was gone,” Freese said. “The Irvine Ranch Conservancy had written up their final report, and they met all of the success criteria, but that report did not get to the agencies in time before the fire hit, so they could not sign off on it,” said Hill. 

After the 2020 Silverado fire, the vegetation was further smothered by mudflow from the hills due to heavy rain. The native plant seeds eventually grew through the layers of earth, and the project was deemed successful by the state and federal wildlife agencies in 2023. 

Silverado Canyon

Although the Lower Silverado Canyon area is also a creekside habitat, it is quite different from Agua Chinon, according to Freese. The restoration area, which spans 28.5 acres, was previously a gravel and sand mining site. Bottom of Form

“The soil was badly disrupted and covered with non-native grasses,” Freese said. “There was a lot of stoney materials to deal with. We took a different approach, with less seeding and more container plants.”

About 11,000 potted plants from a nursery were used to restore the area, according to Collin Raff, Project Manager with Irvine Ranch Conservancy who oversaw the project.

But the following year, the valley flooded, putting a wrench in the progress they had made. “Many of the plants were pulled out and flushed down the river, but some survived… we also had influxes of invasive weeds,” said Freese.

“Flooding is generally a natural process, but it can make the restoration process difficult, because things are changing all the time,” added Raff. 

To address this, they assessed the area for invasive plants and replaced plants that were dispersed by the flood. This project was also deemed successful by the state and federal wildlife agencies in 2023.

Native Plants and Wildfires

Plants native to Southern California are best suited to sustain the region’s wildlife, according to Freese. “These plants evolved with the native wildlife, and there is a balance between the wildlife and the native species,” he said. “When native species are displaced by invasive, highly competitive species, the ecological relationships are impacted. The animals don’t eat them, and the insects don’t know what to do with them. They take up space, but they offer nothing in terms of habitat quality.”

Invasive species are also at a greater risk of catching fire. “A lot of the non-native plants grow very quickly, and then dry out early in the summer and become huge fire hazards,” Freese said. “Native species grow slowly and are less flammable than the weeds.”

Nearly 7,000 wildfires occurred in the state in 2023, much fewer than in previous years. 

Climate change is partly to blame for the increased frequency and severity of wildfires in the state. “The patterns of climate change are there. California has always had a notoriously variable climate, but we are seeing it get more and more extreme,” Freese said. “It is something we have to figure in and build into plans and make the environment as resilient as possible.” 

Native plants help to create resilience in habitats, according to Freese. 

Looking Forward

The Irvine Ranch Conservancy continues to engage in restoration projects with funding from OCTA and other partnerships, namely the installation of a cactus nursery in Silverado Canyon and the enhancement of butterfly habitats in Limestone Canyon, among other projects.