Strengthening the Oaks of Santa Margarita River Trail Preserve
A mature Engelmann oak that acorns were collected from in 2023 | Photo by Zach Kantor-Anaya
One of the core components of The Wildlands Conservancy’s mission is to preserve the beauty and biodiversity of the Earth. At the Santa Margarita River Trail Preserve (SMRTP), that mission is alive across a variety of ecosystems. From the aquatic and riparian areas of the Preserve to the oak woodlands and chaparral dominated slopes above the river, the SMRTP supports a wide array of plant and animal species. The oak woodland plant communities found at SMRTP, and found across coastal California, are well known as being biodiversity hubs — offering both beauty and safe harbor for a multitude of species.
Coast Live Oak trees (Quercus agrifolia ) are a prominent species at the Preserve. Their large densely packed green canopies and wide-spreading branches, cast shady refuge in the summer and bountiful harvest of nutrient rich acorns for wildlife each autumn. Unfortunately, some of the most majestic coast live oak trees on the landscape are threatened by the invasion of a non-native bark beetle, the Golden Spotted Oak Borer (GSOB). Approximately 100,000 coast live oak trees have been killed by the GSOB since it arrived in Southern California from Arizona 20 years ago. The GSOB burrows into the bark of large mature coast live oak trees where it lays its eggs. When those eggs hatch the larvae destroy the vascular system of these decadent oak trees, ultimately leading to the death of these iconic and important California trees.
GSOB grub burrowed in oak | Photo by The Wildlands Conservancy Staff
To protect and restore the oak woodlands of SMRTP, our stewardship team is taking proactive, science-based action. While scientists are working on ways to introduce natural pest control methods to reduce the population and associated impacts of the Golden Spotted Oak Borer, we are investing in the long-term resilience of the oak woodlands.
Studies have shown that the GSOB prefers to lay their eggs in larger diameter, mature oak trees, so our team has planted new generations of oak trees of varying age and size classes. For the past five years, our team has collected acorns from healthy coast live oaks, nurtured them in our native plant nursery, and transplanted the young saplings into protected restoration areas.
This work complements The Wildlands Conservancy’s broader oak conservation initiatives, including the establishment of the Experimental Oak Woodland venue within the Southern California Montane Botanic Garden at Oak Glen Preserve — the newest of 15 unique habitat venues. This project focuses on restoring and conserving native oak woodlands from the ravages of introduced pests, pathogens, and climate change that threaten these critical habitats in the San Bernardino Mountains.
The Wildlands Conservancy is collaborating with the Yuhaaviatam of San Manuel Nation to develop interpretive signage, program curriculum, and interactive kids’ quizzes that engage visitors in learning about oak species and their cultural significance. Three large interpretive signs, two interactive Kids Quizzes, and specialized training for TWC naturalists and docents will enhance school field trips and public programs at the Experimental Oak Woodland venue.
Engelmann Oak sapling planted at SMRTP in January of 2024 | Photo by Zach Kantor-Anaya
We are also enhancing species diversity by cultivating Engelmann oaks (Quercus engelmanni) on the Preserve. The Engelmann Oak is a beautiful oak tree species that has a limited geographic range, only found within coastal Southern California and Baja California. Their distinctive blueish colored foliage and unique bark characteristics make them stand out on the landscape. Importantly, Engelmann oaks are resistant to the Golden Spotted Oak Borer — providing an added layer of protection for the woodland ecosystem. We trust that the work we are putting in to propagate these oak trees will make the oak woodlands more resilient and beautiful for future generations.
By restoring and diversifying oak woodlands, The Wildlands Conservancy is building a more resilient future for this landscape — protecting the beauty, biodiversity, and balance of the Santa Margarita River Trail Preserve for all to enjoy.