On November 30, 2010, the United States Fish and Wildlife Service ("Service") designated approximately 783 acres of land in Riverside and San Diego Counties, California, as critical habitat for the plant San Diego ambrosia (Ambrosia pumila).  This is approximately 329 acres less than the Service had previously proposed.  The Service’s designation excluded approximately 118 acres of critical habitat that fell within the Western Riverside County Multiple Species Habitat Conservation Plan.  In its final economic analysis, the Service estimated that the critical habitat designation would have an incremental cost of less than $9,000 over the next 20 years. 

San Diego ambrosia is distributed from northwestern Riverside County to northwestern Baja California, Mexico.  It grows approximately 2 to 12 inches high and produces yellowish to greenish-colored flowers.