Santa Ana Mountains

The Sinks, Limestone Canyon,
Irvine Ranch Land Reserve
© Harold E. Malde

Halfway between Los Angeles and San Diego is the largest intact natural landscape remaining in coastal southern California - the Santa Ana Mountains, the Santa Margarita River watershed, and the coastal sage scrub communities of central and southern Orange County and northern San Diego County.

Location
Southern California, between Los Angeles and San Diego and between Orange and Riverside Counties. Map

Size
500,000 acres (781 square miles)

Plants
Native needlegrass, Engelmann and coast live oaks, vernal pools, and associated wildflowers.

Least Bell's vireo
© Bruce Farnsworth

Animals
Least Bell's Vireo, California red-legged frogs, foxes, bobcats, mountain lions, grasshopper sparrows, black-shouldered kites, gophers, and badgers.

Why the Conservancy Selected This Site
This natural landscape, one of the largest in the state, is home to a number of declining species and the only year-round, free-flowing river in southern California (the Santa Margarita). The Nature Conservancy has recognized the critical importance of this region by making it a prime conservation priority in the state.

What the Conservancy Has Done/Is Doing
Since 1982, The Nature Conservancy has worked to safeguard this magnificent landscape, together with its partners - the Irvine Company, San Diego State University, Camp Pendleton Marine Base, and the California Wildlife Conservation Board. A historic partnership between land developers from the Irvine Company and land conservationists from The Nature Conservancy has resulted in a stewardship plan for developing long-term habitat management and restoration programs on 21,000 acres of Irvine Ranch Wildlands and Parks canyon land in Orange County. Set aside as a natural sanctuary, the reserve is now managed by the Conservancy.

In 1984, with the purchase of land on the Santa Rosa Plateau, The Nature Conservancy established a foothold in the South Coast region. Since that time, the Conservancy has more than doubled the size of the Santa Rosa Plateau Ecological Reserve. Today, the reserve's 8,300 acres host numerous declining natural communities: Engelmann oak woodlands, riparian woodlands, coastal sage scrub, and vernal pools.

With the increasing threat of large-scale development surrounding the Santa Rosa Plateau, there was a threat to critical wildlife corridors that link the plateau to other protected areas such as the Cleveland National Forest. In danger of becoming an ecological island, the plateau would have been unable to support the long-term health of its native animals and plants. In 1993 the Conservancy launched a broader initiative to protect the entire Santa Margarita River watershed. We have purchased approximately 1,000 acres between the Santa Rosa Plateau and the Cleveland National Forest creating a minimum wildlife corridor and will protect more acres by working with homeowners and other conservation partners in the area.