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Update: Agua Chinon Habitat Restoration

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The project is entering its second year, with many signs of progress.

One of the biggest challenges for any habitat restoration project in the Irvine Ranch Natural Landmarks is access to water. While some projects benefit from leftover cattle trough water lines from the area’s ranching days, other projects need to rely on more creative methods. In the Agua Chinon area of OC Parks’ Limestone Canyon, a nearby municipal water source has made access to water possible, improving the success rate of a 30-acre habitat restoration project. 

However, as visitors to Agua Chinon have noticed, bringing that water from the tank to the plants involves a thick main irrigation line running along the trail, with several smaller lines going off into the planting areas. Not the most natural sight to see, but a true sign of the rehabilitation that continues in this wildlife habitat. Currently the majority of the work is being done in a 17-acre mitigation area funded by OC Waste & Recycling and managed by Irvine Ranch Conservancy. As the project enters its second year, the regular irrigation has meant steady progress in returning this watershed back to a more native environment.


The irrigation has hastened the growth of invasive weeds such as castor bean and tree tobacco. This was actually part of the original restoration plan, since the invasive plants are encouraged to grow, then are removed before they can spread seed. The process clears the soil of the invasive plant species seed, making a more hospitable environment for native plantings.  So far, this “grow-and-kill” strategy has been most effective on castor bean, and Irvine Ranch Conservancy Project Manager Lars Higdon hopes to continue the success as more non-native plant species enter their growth season.

“Through the fall, the mustards were fairly dormant, possibly due to the drought,” said Higdon. “However, as the mustards begin to grow and are cleared from the soil seed bank, the competition for resources will lessen for the newly-planted native species.”

With fewer invasive weeds, native plants will have better access to water, sunlight and other resources needed for successful growth. In December, Conservancy staff and volunteers began planting a few thousand mule fat cuttings, as well as various native plant seedlings. Agua Chinon is at the bottom of the San Diego Creek Watershed – which begins at The Sinks in Limestone Canyon – and the sandy wash area is home to many riparian plants. Further into the canyon, oak seedlings were planted, and some invasive weed removal projects are focusing on areas where the rest of the habitat is mostly native.

The irrigation will continue as the plants mature, which will take 2-3 years. During that time, Conservancy staff will continue to monitor the progress of the native plants and the invasive plant removal. Staff are also monitoring a recent invasion of Argentinean ants, which kill off native ant species. Native ants are beneficial to local habitat because they help spread seed naturally and aerate the soil. Unfortunately, the Argentinean ants are attracted to the steady water source, so land managers will have to continue to balance the goals of native plant health with the need to remove the invasive ant threat.

Planting will continue in the area through the winter, and volunteers are needed to help.  Please visit www.LetsGoOutside.org/Activities to register.