San Rafael State Natural Area (SRSNA) is located in the San Rafael Valley in Santa Cruz County in southern Arizona and is adjacent to the San Rafael de la Zanja Land Grant. These properties combined are referred to as the San Rafael Short Grass Prairie Preserve. San Rafael Short Grass Prairie Preserve comprises 21,131 acres of rolling grassland on the southern end of this valley along the Mexican border. In 1999, Arizona State Parks purchased 3,557 acres on the southern section of The San Rafael Ranch and Cattle Company to conserve one of the last remaining unfragmented remnants of a grassland ecosystem in the U.S. between southern California and west Texas. The remaining 17,574 acres are protected by a Conservation Easement which ensures the property retain its scenic, undeveloped, natural condition and operating cattle ranch. The Conservation Easement is managed by State Parks but is privately owned. The San Rafael Valley extends into northern Sonora, Mexico and has an elevational range from 3,500 to 5,200 feet.Average annual rainfall ranges from 16 to 20 inches.
The San Rafael Valley is known for three major vegetation communities: open, rolling Plains grassland, Madrean evergreen woodland, and riparian deciduous broadleaf woodland. The SRSNA is largely intact native plant community and remains a perennial grass-dominated landscape. A significant feature of the SRSNA is its diversity of plant life. Two hundred and fifty-three plant species have been identified within SRSNA. Some of the perennial grasses identified within SRSNA, which are characteristic of the Plains grassland type, include purple three-awn, four species of grama grasses, plains lovegrass, sacaton, brittlegrass, and vine mesquite. Representative oak and juniper Madrean evergreen woodland species include Arizona White Oak, Emory Oak, and Alligator Juniper. The riparian deciduous broadleaf woodland community is associated with the Santa Cruz River and its springs and tributaries. Representative tree species include Fremont’s Cottonwood, Willow, Velvet Mesquite, and Walnut.
SRSNA has a great diversity of wildlife species stemming from the riparian habitats, associated perennial water sources, and grassland habitats. SRSNA is located within the “Madrean Sky Island’ bioregion which is estimated to have the greatest diversity of mammal species in North America. The SRSNA is also home to the federally listed Huachuca water umbel and Sonora tiger salamander and the candidate species Western yellow-billed cuckoo. Other bird species of interest are the grasshopper and Botteri’s sparrows and the Gray Hawk. Reptile species include Mexican gartersnake, ring-necked snake and ornate box turtle.
Native habitats, endangered species and plant community composition and diversity are impacted by the occurrence of less desirable non-native (also known as invasive) plant and animal species in Arizona. Problem non-native invasive species, due to their potential to invade an area and cause adverse ecological impacts found within SRSNA include Lehmann lovegrass, Weeping lovegrass, Johnsongrass, Tall fescue, the annual species Crabgrass, Jungle rice, Stinkgrass, Pitscale grass, Saltcedar, Tree of Heaven, bullfrogs, mosquitofish, and green sunfish.