Biodiversity Atlas LA

Federal listing: None

State listing: Vulnerable

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Description: The Engelmann oak is a semi-evergreen tree that may be drought-deciduous during the summer. It can reach a height of 18 meters. It has the smallest range of any California oak, and typically occurs in interior foothills and woodlands from Southern California to northern Baja California. Locally, it can be found below 1,300 meters in the San Gabriel and Santa Ana Mountains.

 

Threats: Extensive declines in Engelmann oak habitat have been observed over the past 50 years, and the species is now listed as vulnerable by the IUCN Red List. The main threats to this species include grazing and urban, agricultural, and industrial development, as well as poor regeneration by the species itself. Additionally, climate change could cause losses of 63-76% by the end of the 21st century. Even the best-case, unlimited dispersal scenarios predict losses of 2-34% (net change) in suitable habitat. Climate-driven shifts in habitat could also increase contact between Engelmann oak and individuals of other potentially hybridizing species, such as scrub oaks like

Quercus berberidifolia and Quercus cornelius-mullerii.

 

What We Can Do: Engelmann oaks require increased habitat protection from land development and the projected land use changes in Southern California. Private lands are currently very important for protecting existing populations of this species, but just as important is the protection of habitat corridors between key protected areas. The acorns of Engelmann oak are dispersed by animals, and current patterns of land development and habitat degradation throughout Southern California pose formidable barriers to the species movements. Human-assisted dispersal of the oaks may be needed in the future.