Lower Rincon

Lower Rincon covers 3,278 acres on the basin floor and lower foothills east of the Rincon Mountains, within the Coronado National Forest's Santa Catalina Ranger District in Pima County, Arizona. The terrain is arid basin country anchored by San Juan Hill. The Mescal Arroyo headwaters drain east through the area, joined by Martinez Wash, with year-round water at Bear Spring and stock water at Rock Pile Tank. The watershed connects the lower Rincon flank to the Mescal Arroyo–Cienega Creek system that flows north toward the San Pedro River.

Vegetation reflects a Madrean-edge desert mosaic. Saguaro Cactus and Palo Verde Desert holds saguaro (Carnegiea gigantea), southwestern barrel cactus (Ferocactus wislizeni)—vulnerable on the IUCN Red List—ocotillo (Fouquieria splendens), Palmer's agave (Agave palmeri), and velvet mesquite (Neltuma velutina). Upper Sonoran Desert Scrub, Chihuahuan Desert Mixed Scrub, Chihuahuan Desert Cactus Scrub, and Mojave Creosote Desert occupy the basin floor, with creosotebush (Larrea tridentata), spoonflower (Dasylirion wheeleri), and sacahuista bear-grass (Nolina microcarpa) anchoring the soils. Apache-Chihuahuan Desert Grassland and Chihuahuan-Sonoran Desert Swale Grassland cover open expanses; sand- and clay-bottomed Warm Desert Dry Wash channels cross between them. The foothills rise into Sky Island Pinyon-Juniper Woodland, Sky Island Oak Woodland with Emory's oak (Quercus emoryi) and Mexican blue oak (Quercus oblongifolia), and Arizona Plateau Chaparral with Mexican manzanita (Arctostaphylos pungens). Along Mescal Arroyo and Bear Spring, Warm Desert Mountain Streamside Woodland holds Wright's sycamore (Platanus wrightii), Arizona black walnut (Juglans major), Fremont cottonwood (Populus fremontii), Goodding's willow (Salix gooddingii), and netleaf hackberry (Celtis reticulata).

Wildlife stacks across the elevation transition. Along the streamside woodland and wash bottoms, lowland leopard frog (Lithobates yavapaiensis), canyon treefrog (Dryophytes arenicolor), and Sonora mud turtle (Kinosternon sonoriense)—vulnerable on the IUCN Red List—use the pools at Bear Spring and the perennial reaches. Gray hawk (Buteo plagiatus), zone-tailed hawk (Buteo albonotatus), and northern beardless-tyrannulet (Camptostoma imberbe) hunt and nest in the riparian canopy. On the desert flats, Sonoran desert tortoise (Gopherus morafkai), also IUCN vulnerable, browses on cholla and grasses; Gila monster (Heloderma suspectum) and ornate box turtle (Terrapene ornata)—both IUCN near threatened—use the chaparral and oak woodland edges; greater roadrunner (Geococcyx californianus), black-throated sparrow (Amphispiza bilineata), and varied bunting (Passerina versicolor) work the saguaro and desert grassland. Montezuma quail (Cyrtonyx montezumae) and Arizona woodpecker (Dryobates arizonae) hold in the oak woodland; mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), and coyote (Canis latrans) move through the basin and foothills. Olive-sided flycatcher (Contopus cooperi), near threatened on the IUCN Red List, passes through during migration. Portions of this area fall within the potential range of several federally listed species; see the Conservation section for details.

Crossing the Mescal Arroyo basin toward San Juan Hill, a visitor passes through creosote and saguaro, then into the dry shade of mesquite and sycamore where Bear Spring runs in the rock. Greater roadrunners flush from the wash bottom; a Sonoran desert tortoise pulls into the shade of a Mexican blue oak. Climbing up the slope toward the Rincon foothills, the view opens west across the basin toward the high Rincon Mountains and east toward the Galiuro range.

Lower Rincon is a 3,278-acre Inventoried Roadless Area within the Coronado National Forest in Pima County, Arizona. The area is managed within the Santa Catalina Ranger District and lies in the U.S. Forest Service's Southwestern Region, draining the Mescal Arroyo headwaters east of the Rincon Mountains. The area is protected under the 2001 Roadless Area Conservation Rule.

From 200 to 1450 A.D. people archaeologists call the Hohokam lived in villages near present-day Saguaro National Park, venturing into both the Rincon and Tucson Mountains to hunt and gather native foods to supplement their dry-farming crops of corn, beans, and squash [1]. The Sobaipuri people of the Tucson Basin and their Tohono O'odham neighbors to the west subsequently adopted a simpler lifestyle better fitted to desert realities, hunting deer, rabbits, and other game and harvesting cholla buds, prickly pears, and palo verde pods [1]. The Tohono O'odham trace their origins to the Hohokam, who settled along the Salt, Gila, and Santa Cruz Rivers thousands of years ago and built sophisticated canal systems to irrigate crops of cotton, tobacco, corn, beans, and squash [4]. Even after Arizona became a U.S. territory, Apaches often returned home over and around the high Rincon Mountains [1]. The Gadsden Purchase of 1853 divided O'odham land almost in half between the United States and Mexico [4].

The Nequilla Mine, located on December 11, 1865 just south of present Saguaro National Park, was patented on September 28, 1872, making it the first patented mining claim in the Arizona Territory [3]. In 1872, Manuel Martinez began his Cebadilla Ranch in the valley below Tanque Verde Ridge, planted 400 fruit trees, and brought in cattle [1]. By 1880, the Campos, Van Alstine, Oury, and Carrillo families ran over 1,200 head of cattle on public rangelands that would become Saguaro National Park [1]. The railroad reached Tucson in 1880, and the Apache Wars ended with Geronimo's surrender in 1886 [1].

The first move toward federal protection of the lands surrounding Lower Rincon was the creation of the Santa Rita Forest Reserve on April 11, 1902, followed in July of that year by the Santa Catalina Forest Reserve, Mount Graham Forest Reserve, and Chiricahua Forest Reserve [2]. On July 2, 1908, Executive Order 908 consolidated the Dragoon, Santa Catalina, and Santa Rita National Forests to establish the Coronado National Forest [5]. On October 23, 1953, 425,674 acres of the Crook National Forest were transferred to the Coronado, completing the forest's modern shape [2]. In 1933, University of Arizona president Homer Shantz convinced President Hoover to set aside Saguaro National Monument in the Rincon Mountains [1]; this protected area now adjoins Lower Rincon along the western side of the range. The roadless designation under the 2001 Roadless Area Conservation Rule preserves the lower-elevation desert and chaparral approach to the Rincons on Coronado National Forest lands east of the national park.

Vital Resources Protected

• Mescal Arroyo Headwater Protection: Lower Rincon's 3,278 roadless acres include the Mescal Arroyo headwaters and Martinez Wash, with Bear Spring supplying perennial flow into the otherwise dry basin. Keeping the bajada and foothill slopes uncut allows infrequent monsoon rainfall to infiltrate the soil rather than running directly off bare surfaces, recharging shallow aquifers and emerging as low-sediment baseflow. This headwater function sustains pool habitat for Sonora mud turtle (Kinosternon sonoriense), vulnerable on the IUCN Red List, and lowland leopard frog.

• Riparian Function in Streamside Woodland: Warm Desert Mountain Streamside Woodland traces the perennial reaches of Mescal Arroyo and Bear Spring, anchored by Wright's sycamore (Platanus wrightii), Arizona black walnut (Juglans major), Fremont cottonwood (Populus fremontii), and Goodding's willow (Salix gooddingii). The intact upland slopes dampen flash-flood pulses and sustain dry-season baseflow. This streamside canopy shades creek pools, traps sediment, and provides nesting and foraging habitat for gray hawk (Buteo plagiatus), zone-tailed hawk (Buteo albonotatus), and northern beardless-tyrannulet (Camptostoma imberbe).

• Sky Island–Saguaro NP Connectivity: Lower Rincon adjoins Saguaro National Park (Rincon Mountain District) on the western flank of the Rincon Mountains, with continuous Sky Island Oak Woodland, Sky Island Pinyon-Juniper Woodland, Chihuahuan Desert Mixed Scrub, and Apache-Chihuahuan Desert Grassland extending the protected national-park canopy across the Coronado National Forest. The roadless condition allows Sonoran desert tortoise (Gopherus morafkai), Gila monster (Heloderma suspectum), and large carnivores to move between the national park and the broader Coronado landscape without crossing a road network.

Potential Effects of Road Construction

• Sedimentation into Mescal Arroyo Pools: Road construction across the steep foothill slopes that drain into Mescal Arroyo and Martinez Wash would expose mineral soil on cut and fill faces. Surface runoff would deliver fine sediment directly into the pools at Bear Spring and the perennial reaches downstream, filling the interstitial substrates that aquatic invertebrates, Sonora mud turtle, and lowland leopard frog depend on. Cut slopes continue to shed material for years after construction, producing chronic rather than one-time sediment loading.

• Fragmentation of Sky Island–Park Connectivity: A road corridor cut through Lower Rincon would slice through habitat that currently extends continuous from the Coronado National Forest into Saguaro National Park. NatureServe assessments identify roads as a pervasive threat to wide-ranging species such as ocelot (Leopardus pardalis) and Mexican wolf (Canis lupus baileyi) in this region. Re-establishing crossings across a hard linear feature requires either bridges, culverts, or fencing schemes that approximate—but never replicate—an unbroken canopy.

• Buffelgrass Invasion in Saguaro–Palo Verde Desert: Construction equipment and the bare, regularly disturbed surface of a new road act as a vector and seedbed for non-native annual grasses such as buffelgrass (Pennisetum ciliare), already documented as a pervasive threat to Saguaro Cactus and Palo Verde Desert in this region. Once established, buffelgrass and similar annuals carry fast-moving fires through saguaro stands that are not adapted to repeated burning. Each subsequent fire favors more grass over native saguaro and palo verde, making the change effectively permanent.

Lower Rincon covers 3,278 acres of basin and lower foothills east of the Rincon Mountains, in the Coronado National Forest's Santa Catalina Ranger District in Pima County. The area contains no maintained trails, no designated trailheads, and no developed campgrounds. Recreation is dispersed and unguided. Access is on foot from the surrounding Forest road network and from adjacent Saguaro National Park access points on the Rincon Mountain side. Visitors should expect open desert and dry washes, intermittent water at Bear Spring, and intense summer heat in the arid basin.

Hunting in and around the area follows Arizona Game and Fish Department regulations for the units that include the Rincon foothills and the Mescal Arroyo basin. The mosaic of saguaro-palo verde desert, desert grassland, chaparral, and pinyon-juniper-oak woodland supports general hunts; Gambel's quail, mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), and collared peccary (Pecari tajacu) range the basin and foothills, while Montezuma quail (Cyrtonyx montezumae) hold in the oak edges. Hunters should verify current AZGFD seasons and unit boundaries before entering.

Birding around Lower Rincon is exceptionally well-documented. Twenty eBird hotspots fall within 24 km of the area, anchored by Benson STP (251 species, 4,270 checklists), Cienega Creek Preserve (207 species, 1,190 checklists; permit required), Benson–San Pedro Golf Course (203 species), and Paige Creek (183 species, 913 checklists). La Posta Quemada Ranch (176 species), Rincon Mountains–Miller Creek Trailhead (145 species), and several Saguaro National Park East locations document the Sky Island and basin avifauna. Within Lower Rincon itself, gray hawk (Buteo plagiatus), zone-tailed hawk (Buteo albonotatus), northern beardless-tyrannulet (Camptostoma imberbe), and Bell's vireo (Vireo bellii) work the streamside woodland along Mescal Arroyo; greater roadrunner (Geococcyx californianus), black-throated sparrow (Amphispiza bilineata), and varied bunting (Passerina versicolor) hold in the saguaro and desert grassland.

Mescal Arroyo and the pools at Bear Spring hold small amounts of perennial water; fishing here is not a primary activity because the drainage is intermittent. Sonora mud turtle (Kinosternon sonoriense), canyon treefrog (Dryophytes arenicolor), and lowland leopard frog (Lithobates yavapaiensis) use these pools, and quiet observation is the most productive way to encounter them. Photographers find strong views of the high Rincon Mountains rising west of the basin, with the saguaro-palo verde flats and oak-juniper foothills in the foreground.

Because there are no Forest roads inside Lower Rincon, every activity—descending into the Mescal Arroyo basin, birding the streamside woodland at Bear Spring, hunting the foothill mosaic, photographing the Rincon Mountains across an unbroken foreground, scouting routes toward Saguaro National Park—depends on a foot approach from the surrounding road network. A road corridor would shorten the walk-in but would fragment the unbroken desert-to-foothill canopy that connects Coronado lands to Saguaro National Park, deliver sediment and noise to the Mescal Arroyo pools, and remove the backcountry character that distinguishes the roadless area from the more developed parts of the Tucson metropolitan basin.