Oak Woodlands
The oak woodlands of the western Sierra foothills are one of the most imperiled habitats in all of California. These oak woodlands, where approximately 70% of the region’s population lives, have been hardest hit by development. Less than 1% of the foothills’ are protected from development, and much of the area lies within commuting distance of rapidly growing cities in the Central Valley.
The Sierra Nevada Ecosystem Report of 1996 reported that "The oak woodland communities of the western Sierra Nevada foothills are the most vulnerable of the widespread vegetation types as a result of greater access by humans and of their continuing potential for urban development,”"(Vol I, page 18).
More than 65% of the oak woodlands in the Sierra Nevada region are privately owned and with continuing increases in land values these landscapes can be worth far more when converted to housing or intensive agriculture such as vineyards.
The clearing of oak woodlands for development has a tremendous ecological impact by degrading water quality and wildlife habitat. These habitats are among the most critical for California’s native species, including some 2,000 plants as well as 5,000 insects, 80 amphibians and reptiles, 160 birds and 80 mammals. Oak woodlands are also key to water quality concerns. As snowmelt flows down watersheds into streams and rivers, oaks help keep the soil in place, preventing erosion and stream sedimentation.
Oaks are most susceptible during the transition from seedling to sapling, and the main threats include overgrazing by cattle, and competition from the nonnative annual grasses that have replaced native perennial grasses. State researchers have determined that providing enclosures for young oak seedlings to prevent grazing by cattle goes a long way to ensuring their survival.
California's iconic oak woodlands have endured many assaults over the years. They've been cut for fuel, cleared for vineyards and housing developments, and their seedlings face intense grazing pressure and competition from invasive grasses. But the future also brings the new threat of climate change. Researchers have determined that the areas of the state where the climate is suitable for these oak species to grow will shift northward and could shrink to nearly half their current size as a result of global warming.