San Diego National Wildlife Refuge protects inland habitat in California’s San Diego backcountry within a larger refuge complex. Its coastal sage scrub, chaparral, oak woodland, and freshwater marsh preserve some of the region’s remaining open land and support sensitive species such as the endangered least Bell’s vireo and California gnatcatcher, the rare Quino checkerspot butterfly, and the San Diego horned lizard. The refuge also contributes to the Multiple Species Conservation Plan through the Otay-Sweetwater Unit, helping conserve connected habitat while development is directed to less sensitive areas. Its approved boundary includes 44,000 acres, with continuing surveys as more land is acquired.