DENNERY CANYON HABITAT RESTORATION PROJECT

Unique Shrublands of Baja California… In the United States

The Chaparral Lands Conservancy proposes a project to restore and enhance rare habitats and species in Dennery Canyon, a regional habitat preserve in the City of San Diego community of Otay Mesa.

Not far from the International border with Mexico and just a few miles from the ocean there is a secluded canyon supporting a small area of the rich nature of Baja California… in the United States. Located at the western end of the City of San Diego community of Otay Mesa, Dennery Canyon supports unique and rare vegetation, maritime succulent scrub, coastal sage scrub, and native grasslands as well as several dependent imperiled species. Recent conservation property purchases in the canyon now provide an excellent opportunity for habitat restoration projects to reverse harm from years of neglect and off-road vehicle abuse.

Property owned by several agencies in Dennery Canyon forms a crucial conservation core area under the San Diego Multiple Species Conservation Plan (MSCP) and is a critical element of natural infrastructure in the Otay Mesa community. Two agencies own the majority of preserved land in Denery Canyon: The California Department of Transportation (Caltrans) owns a 90 acre property in Dennnery Canyon for the primary purpose of restoring vernal pool habitat as mitigation for the nearby S.R. 905 freeway project. And the City of San Diego owns several properties. The Conservancy’s proposed Dennery Canyon Habitat Restoration Project would specifically restore and enhance coastal sage scrub, maritime succulent scrub, and native grassland vegetation in areas of Caltrans and City property that have not been used for mitigation. The agencies’ preserved properties are adjacent to the “Cal Terraces” vernal pool mitigation.The majority of native vegetation found in Dennery Canyon is unique and imperiled – Maritime succulent scrub, coastal sage scrub, native grasslands, and vernal pools. Dennery Canyon also supports an extremely rare and interesting intrusion of more typical desert vegetation on patches of Linne soils. These vegetation communities in turn support habitat for numerous rare species, several of which like the California gnatcatcher, San Diego fairy shrimp, Otay tarplant, and San Diego coyote thistle are federally listed endangered species.

Dennery Canyon is also a conservation paradox. Recent suburban development around the rim of the canyon has partially isolated the area from other natural open space. Such isolation can be harmful when animal movement corridors are blocked and the edge effects of surrounding development creep into adjacent natural open space – Escaped exotic landscaping plants and weeds, trash dumping, hunting housecats, leaking sprinklers, and more. But several hundred acres of Dennery Canyon are in conservation ownership and the canyon is large enough and deep enough to serve as an effective and isolated refuge for nature. The same development that has mostly isolated the canyon from other larger open space also blocks access by off-road vehicles. And Dennery Canyon is better protected from unnaturally frequent fire than other larger and more connected open space as large Santa Ana driven fires from the east are more likely to be halted at the edge of surrounding development before reaching the canyon.

Over the last several years dedicated agency employees have worked diligently to improve resource conditions in Dennery Canyon through patrols, installation of fencing and vehicle barriers and signs, and cleaning up trash. Agencies have been particularly successful in reducing major past illegal off-road vehicle activity and have recently installed effective vehicle barriers. Caltrans has funded the active restoration of several acres of previously severely degraded vernal pools and has included measures to increase populations of the critically endangered Burrowing owl.

Yet only a few years have passed since Dennery Canyon was overrun on weekends and holidays with off-road vehicles so there is still an outstanding unfulfilled need to improve the condition of several imperiled species and habitats that were impacted prior to establishment of preserved areas. Proactive management measures are also needed to fulfill the goals of the MSCP for covered species, especially since recent suburban development around the rim of Dennery Canyon has introduced new harmful edge effects. In cooperation with Caltrans and the City of San Diego, The Chaparral Lands Conservancy proposes to address these issues with a project to restore and enhance rare uplands habitats and dependent species.

THE PROPOSED DENNERY CANYON HABITAT RESTORATION PROJECT

The proposed Dennery Canyon Habitat Restoration Project would restore approximately 11 acres of coastal sage scrub, maritime succulent scrub, and native grasslands consistent with the goals of the MSCP.

Much of the rare uplands habitat in Dennery Canyon has been seriously impacted over decades, first by grazing and then by concentrated off-road vehicle use. These disturbances in turn resulted in the introduction and spread of competing exotic invasive weeds. Under the proposed project, degraded coastal sage scrub, maritime succulent scrub, and native grasslands would be restored or enhanced through weeding and plantings for the benefit of these habitats and dependent MSCP covered species. The project would also benefit other adjacent sensitive habitats and reduce erosion into community waterways. Particular emphasis would be placed on enhancing populations of the endangered San Diego cactus wren, Otay tarplant, and San Diego thornmint among others of the rarest Dennery Canyon species. Improved conditions for uplands habitats would in turn improve habitat conditions for nearby vernal pools and other sensitive species and habitats by improving watershed conditions, expanding habitat for pollinators, reducing weed sources, and other values.

REQUEST FOR ENDORSEMENT AND SUPPORT

The Chaparral Lands Conservancy respectfully requests endorsement and support for the Dennery Canyon Restoration Project by conservation groups, community groups, planning groups, homeowner’s associations, elected officials, community leaders, and others. The Conservancy is currently seeking funding to retain expert habitat restoration contractors to carry out proposed habitat and species restoration work. Funding is also being sought for public outreach activities such as volunteer work parties, signs, and newsletters.

The Chaparral Lands Conservancy has submitted a grant application to the California State Parks Off-Highway Motor Vehicle Recreation Division (OHMVRD) to fund the Dennery Canyon Habitat Restoration Project. Please visit the OHMVRD website for more information on safe and responsible OHV recreation and our grant application. Please report any off-road vehicle activity in Dennery Canyon and Otay Mesa to the San Diego Police Department: 619 424-0400; sdpdsouthern@pd.sandiego.gov and San Diego County Sheriff: 858 974-2222.

For more information on the Dennery Canyon Restoration Project, or The Chaparral Lands Conservancy, please contact us.