California oak woodlands are a plant community found throughout California and northwestern Baja California. Oak woodlands are widespread at lower elevations covering roughly 10% of California’s land area and providing many essential ecological functions. They play a critical role in protecting soils from erosion and landslides, regulating water flow in watersheds, and maintaining water quality in streams and rivers. Oak woodlands also have high levels of biodiversity supporting around 300 terrestrial vertebrate species, 1100 native vascular plant species, 370 fungal species and an estimated 5000 arthropod species.
California’s oak woodlands have been dramatically reduced in extent over the past 230 years. The complex biological web of animals and plants have been fragmented or replaced by agricultural fields, highways, and cities while once common species have become extirpated or extinct. Sapling populations in a number of oak woodlands are inadequate to offset mortality and maintain stand densities in areas unaffected by goldspotted oak borer. GSOB infestation is compounding this on-going oak tree mortality occurring on federal, state, private, and Native American lands in San Diego County.
Without natural regeneration woodlands gradually thin to open oak savannas, which in turn are converted to grasslands dominated by non-indigenous and invasive annuals. People are increasingly aware of the rate of global species extinctions and the loss of natural vegetation. It is important to understand that the loss of biological diversity does not occur only in exotic places such as tropical rain forests. To minimize these losses, affected areas need to actively work to restore and manage remnant oak woodland communities.