The Nature Reserve of Orange County (NROC) contains approximately 6,000 acres of nonnative annual grasslands and highly degraded scrubland in need of restoration to ecologically appropriate native habitats. Cattle grazing was terminated a short time after the Reserve was established in 1996. However, in most cases this did not result in the passive recovery of native habitat that was expected. Most of these areas are ecologically ‘stuck’ and do not recover without active intervention. Frequent fires have exacerbated these issues over time, leading to a significant decline in native species diversity and altering the species composition, particularly within the Central Reserve.
In 2019, the Habitat Restoration and Enhancement Plan (HREP) for NROC was updated to include active restoration and enhancement methods, such as mechanical (e.g., weed trimmers) and chemical methods (i.e., herbicides), followed by native seed addition. The HREP is a blueprint for cost-effective, high-quality habitat restoration projects at the scale of 10s to 100s of acres at a time. Despite this progress, there is still a need to address thousands of acres infested with nonnative vegetation. Given the challenges of managing weeds on such a large scale using mechanical and chemical methods alone, the Natural Communities Coalition (NCC) is exploring conservation grazing as an additional integrated weed management approach.
The Weir Canyon Pilot Conservation Grazing Project, scheduled from 2025 to 2030, aims to address the need for a timely, cost-effective, and practical solution for managing thousands of acres of nonnative annual grassland found within the Reserve. This pilot project, covering approximately 200 acres in Weir Canyon on OC Parks Open Space (see map below), will assess the effectiveness of managed cattle grazing in meeting conservation goals. Cattle are preferred for their grass-eating habits, leaving native coastal sage scrub and oak woodland plants largely undisturbed. By combining conservation grazing with targeted use of herbicide for unpalatable invasive plants and supplemental native seed addition, the project expects that native plants will eventually regain dominance in the landscape.
The compatibility of cattle grazing with native plant recruitment and wildlife habitat benefits is not well understood. Therefore, NCC worked with its Technical Advisory Committee and the State and Federal wildlife agencies to develop an ecosystem study for the pilot project with replication and appropriate controls to evaluate the effectiveness of conservation grazing and the benefits and constraints to wildlife (see map below). A suite of wildlife species along with their habitats, are being closely monitored.
Integrating conservation grazing with mechanical and chemical weed management, in unison with native seeding, offers a promising strategy for restoring the habitat value of thousands of acres, benefiting grassland birds, reptiles, and native plant communities. The Weir Canyon Pilot Conservation Grazing Project aims to contribute valuable insights into the effectiveness of this approach on the Reserve and other conserved lands in California.
For additional information please contact Levi Gray (Natural Resource Management Coordinator) at NCC (lgray@occonservation.org).