Saguaro National Park in southern Arizona is part of the National Park System in the United States. The park land consists of two distinct areasâ€"the Tucson Mountain District (TMD) west of the city of Tucson and the Rincon Mountain District (RMD) east of the cityâ€"that preserve Sonoran Desert landscapes and diverse fauna and flora, including the giant saguaro cactus. The volcanic rocks on the surface of the TMD differ greatly from the surface rocks of the RMD; over the past 30 million years, crustal stretching associated with the Basin and Range displaced rocks from beneath the Tucson Mountains to form the Rincon Mountains. Uplifted, domed, and eroded, the Rincon Mountains remain significantly higher and wetter than the Tucson Mountains, and the higher elevations of the RMD support plant and animal populations that do not exist in the TMD.
Earlier residents of and visitors to the lands in and around the park before its creation included the Hohokam, Sobaipuri, Tohono O'odham, Apaches, Spanish explorers, missionaries, miners, homesteaders, and ranchers. In 1933, President Herbert Hoover, using the power of the Antiquities Act, established the original park as Saguaro National Monument. In 1961, President John F. Kennedy added the TMD and re-named the original tract the RMD. Congress combined the TMD and the RMD to form the national park in 1994.
Hiking on the park's 165 miles (266Â km) of trails and sightseeing along loop drives near the park's visitor centers are popular activities. Both districts have picnic areas and allow bicycling and horseback riding on selected roads and trails. The TMD forbids overnight camping, but the RMD supports limited wilderness camping. Both districts offer ranger-led walking tours and other educational programs.
Names
The park gets its name from the saguaro (Carnegiea gigantea), a large cactus that is native to the Sonoran Desert and that does not grow naturally elsewhere. Rincónâ€"as in Rincon Mountains, Rincon Creek, and Rincon Valleyâ€"is Spanish for corner. The name Tucson derives from Papago-Piman words meaning dark spring or brown spring. Tank or Tanque refers to a small artificial pool behind a dam that traps runoff in an existing natural depression.
Geography and climate
The park consists of two separate parcelsâ€"the Tucson Mountain District (TMD) to the west and the Rincon Mountain District (RMD) to the eastâ€"the nearest parts of which each lie about 10 miles (16 km) from the center of the city of Tucson, Arizona. Their total combined area in 2016 was 91,716 acres (37,116 ha). The TMD covers about 25,000 acres (10,000 ha), while the much larger RMD accounts for the balance of about 67,000 acres (27,000 ha). About 71,000 acres (29,000 ha) of the park, including large fractions of both districts, is designated wilderness.
Each district has a visitor center within easy reach by car from Tucson, and Interstate 10, the nearest major highway. Tucson Mountain Park abuts the south side of the TMD, and the Avra Valley lies immediately east of the TMD. The Rincon Mountain Wilderness, a separate protected area of about 37,000 acres (15,000Â ha), in the Coronado National Forest abuts the RMD on the east and southeast, while the Rincon Valley lies immediately south of the western part of the RMD.
Both districts conserve tracts of the Sonoran Desert, including ranges of significant hills, the Tucson Mountains in the west and the Rincon Mountains in the east. Elevations in the TMD range from 2,180 to 4,687 feet (664 to 1,429 m), the summit of Wasson Peak. The TMD, which consists mainly of desert scrub and desert grassland, receives an average of about 10 inches (250 mm) of precipitation a year. Elevations within the RMD vary from 2,670 to 8,666 feet (814 to 2,641 m) at the summit of Mica Mountain. Annual precipitation varies from about 12 inches (300 mm) in the TMD to 30 inches (760 mm) at high elevations in the RMD. Some of the precipitation at the highest elevations in the Rincons comes in the form of snow from winter storms; snowmelt adds to the limited water available at lower elevations later in the year. Park use is most heavy between October and April, when daytime temperatures reach 70 to 80 °F (21 to 27 °C), and nighttime temperatures may drop below freezing. During the warmest season, May through September, daily high temperatures average more than 100 °F (38 °C). Studies of the effects of climate change on the park show that its annual mean temperature has risen from about 63 °F (17 °C) in 1900 to about 67 °F (19 °C) in 2010.
Saguaro National Park lies within the watershed of the north-flowing Santa Cruz River, which is generally dry. Rincon Creek in the southern part of the RMD, free-flowing for at least part of the year, has the largest riparian zone in the park. The creek is a tributary of Pantano Wash, which crosses Tucson from southeast to northwest to meet Tanque Verde Wash. The two washes form the Rillito River, another dry wash, an eastâ€"west tributary of the Santa Cruz River. The washes in both districts are usually dry but are subject at times to flash floods. Smaller riparian zones are found near springs and tinajas in the RMD. The largest of the springs is at Manning Camp, high in the Rincons.
Geology
The Tucson Basin and nearby mountainsâ€"including the Tucson Mountains to the west, the Santa Catalinas to the north, and the Rincons to the eastâ€"as well as Saguaro National Park, are part of the Basin and Range Province extending from northern Mexico to southern Oregon in the United States. The Basin and Range is of relatively recent geologic origin. Saguaro National Park's oldest rocks, the Pinal Schist, pre-date the formation of the Basin and Range by about 1.7 billion years. The schist is exposed in the RMD along a dry wash off Cactus Forest Loop Drive. Other ancient rocks, 1.4-billion-year-old altered granites, form much of Tanque Verde Ridge in the RMD.
Much later, about 600 million years ago, shallow seas covered the region around present-day Tucson; over time that led to deposition of sedimentary rocksâ€"limestones, sandstones, and shales. Limestone, which occurs in the park in several places, was mined here in the late 19th century to make mortar. The future park land had six lime kilns, two in the TMD, and four in the RMD. Three, all in the RMD, can be visited todayâ€"two along the Cactus Forest Trail and one along the Ruiz Trail.
About 80 million years ago tectonic plate movements induced a period of mountain building, the Laramide orogeny, in western North America. Explosive volcanic eruptions formed the Tucson Mountains, and the roof of the volcano at their center collapsed to form a caldera 12 miles (19Â km) across. Subsequent lava flows, debris flows, and the intrusion of a granitic pluton eventually filled the caldera. Volcanic rocks exposed in and near the TMD in the 21st century are remnants of these events. Examples include large breccia exposed at Grants Pass and a granitic remnant of the magma chamber, which is visible from the Sus Picnic Area in the TMD. However, not all of the molten granite reached the surface of the Tucson Mountains; instead, it cooled and crystallized far below.
Formation of the Basin and Range began when plate movements stretched and thinned the Earth's crust in this part of western North America until the crust pulled apart along faults. The Catalina Fault, a low-angle detachment fault, began to form about 30 million years ago about 6 to 8 miles (10 to 13Â km) below the surface of the Tucson Mountains. The rocks under the fault, the lower-plate rocks, were eventually displaced 16 to 22 miles (26 to 35Â km) east-northeast relative to the rocks above the fault, then uplifted, domed, and eroded to form the Santa Catalina and Rincon mountains visible today. Although the volcanic rocks seen on the surface of the TMD are not found in the RMD, the crystallized granite (Catalina gneiss) from beneath the Tucson Mountains was eventually exposed on the RMD's surface. The most common rock type in the Rincon Mountains, this banded gneiss is visible in the RMD at sites such as Javelina Rocks along the Cactus Forest Loop Drive.
History
Early
The earliest known residents of the land in and around what later became Saguaro National Park were the Hohokam, who lived there in villages between 200 and 1450 A.D. Hunting and gathering wild foods, they also grew corn, beans, and squash. Petroglyphs and bits of broken pottery are among Hohokam artifacts found in the park. Subsequent indigenous cultures, the Sobaipuri of the Tucson Basin and the Tohono O’odham to the west may be descendants of the Hohokam, though the evidence is inconclusive. The Hohokam hunted deer and other animals and gathered cholla buds, prickly pears, palo verde pods, saguaro fruit, and other plant foods to supplement their diet.
Spanish explorers first entered Arizona in 1539â€"40. Non-native settlement of the region near the park did not occur until 1692 with the founding of San Xavier Mission along the Santa Cruz River, which flowed through Tucson. In 1775, the Spaniards built Presidio San Augustin del Tucson, a military fort in what was then part of New Spain, in part to protect against raids by Apaches.
The lands that eventually would become Saguaro National Park remained relatively free of development until the mid-19th century, after Arizona had become part of the United States. After passage of the Homestead Act of 1862, the arrival of the railroad in 1880, and the end of the Apache Wars in 1886, miners, homesteaders, and ranchers established themselves in the Tucson and Rincon Mountains. Miners sought silver, copper, and other valuable ores and minerals. The defunct Loma Verde Mine is still visible in the RMD. It produced a small amount of copper and gold between 1897 and 1907. Ranchers grazed thousands of cattle on public land that would later become part of the park, and homesteaders farmed and ranched at the base of the Rincons, filing homestead applications from the 1890s through 1930. The remains of the former Freeman Homestead, established in 1929, lies along a nature trail in the RMD. The homestead is on the Arizona State Register of Historic Places. Manning Cabin, built in 1905 as a summer retreat for Levi Manning, a wealthy businessman and one-term mayor of Tucson, is part of the infrastructure at Manning Camp near Mica Mountain. Modified and restored after falling into disrepair, it was added to the National Register of Historic Places in 1975. Cultural resources in the park include more than 450 archeological sites and more than 60 historic structures.
After 1920
In 1920 members of the Natural History Society of the University of Arizona expressed interest in establishing a protected area for saguaro, a cactus species familiar to watchers of silent-movie Westerns. In 1928 Homer L. Shantz, a plant scientist and the university's president, joined the efforts to create a saguaro sanctuary. However, issues related to funding and management delayed the creation of a park. In 1933 Frank Harris Hitchcock, publisher of the Tucson Citizen, former United States Postmaster General, and a force in the Republican Party, persuaded U.S. President Herbert Hoover to create Saguaro National Monument. Hoover used his power under the Antiquities Act of 1906 to create the monument by proclamation on March 1, 1933. Later in 1933 President Franklin D. Roosevelt transferred management of the new monument to the National Park Service. Between 1936 and 1939, during the Roosevelt administration, the Civilian Conservation Corps (CCC) built the monument's Cactus Forest Loop Drive and related infrastructure. The monument's visitor center opened in the 1950s.
In 1961 President John F. Kennedyâ€"urged on by Stewart Udall, an Arizonan who was then Secretary of the Interiorâ€"added 16,000 acres (6,500 ha) of cactus lands in the Tucson Mountains to the monument. This western district of the monument was carved from Tucson Mountain Park, managed by Pima County. In the 1920s, the Tucson Game Protective Association had persuaded the Department of the Interior to withdraw about 30,000 acres (12,000 ha) in the Tucson Mountains from homesteading and mining and to set it aside as a park and game refuge. Land leased by the county in this set-aside became Tucson Mountain Recreation Area in 1932. Between 1933 and 1941 CCC workers built structures at eight picnic areas in the county park portion of the set-aside, five of which later became part of the TMD of the national monument. They also worked on erosion control, water supplies for wildlife, road, trails, and landscaping. Kennedy's 1961 proclamation created the TMD from the northern part of the county park and renamed the original monument lands east of Tucson the RMD. Expansions in 1976 and 1994 brought the total TMD acreage to 24,818 acres (10,043 ha). In 1994 Congress elevated the combined TMD and RMD to National Park status.
Biology
Plants and fungi
Plant communities within the park vary with elevation. The TMD has two distinct communities, desert scrub at the lowest elevation and desert grassland a bit higher. The RMD includes these two communities as well as four more at higher elevations, oak woodland, pineâ€"oak woodland, pine forest and, high in the Rincons, mixed conifer forest. During annual inventories in 2011 and 2013, hundreds of scientists and thousands of volunteers identified 389 species of vascular plants, 25 of non-vascular plants, and 197 species of fungi in Saguaro National Park.
Saguaros, which flourish in both districts of the park, grow at an exceptionally slow rate. The first arm of a saguaro typically appears when the cactus is between 50 and 70 years old though it may be closer to 100 years in places where precipitation is very low. A mature saguaro may grow up to 60 feet (18Â m) tall and weigh up to 4,800 pounds (2,200Â kg) when fully hydrated. The total number of saguaros in the park is estimated at 1.8Â million, and 24 other species of cactus are abundant in the park. The most common of these are the fishhook barrel, staghorn cholla, pinkflower hedgehog, Engelman's prickly pear, teddybear cholla, and jumping cholla.
Invasive plants include fountain grass, tamarisk, Malta starthistle, and many others, but by far the most severe threat to the native ecosystem is buffelgrass. This drought-tolerant plant, native to parts of Africa and Asia, was imported to the United States in the 1930s and planted near Tucson and elsewhere to create cattle forage and to control erosion. First detected in the park in 1989, it has dispersed widely in both districts. Competing with other plants for sustenance, buffelgrass fills the empty spaces normally found between native desert plants and creates a significant fire hazard. The noxious weed, considered impossible to completely eliminate, is managed in some areas of the park and in Tucson residential zones by hand-pulling and, during periods of wet weather, application of glyphosate-based herbicides.
Animals
An inventory of medium and large mammals in the park confirmed the presence of 30 species in Saguaro National Park between 1999 and 2008. Of these, 21 were found in the TMD and 29 in the RMD. A partial list of the park's mammals includes cougars, coyotes, bobcats, white-tailed deer, mule deer, javelinas, gray foxes, black-tailed jackrabbits, desert cottontails, ring-tailed cats, white-nosed coatis, ground squirrels, and packrats. One endangered mammal, the lesser long-nosed bat, lives part of the year in the park and part of the year in Mexico.
The wide range of habitats in the park supports a diverse population of birds including some, such as the vermilion flycatcher and the whiskered screech owl, uncommon elsewhere in the United States. Among the 107 bird species found in the park are great horned owls, cactus wrens, ravens, kestrels, turkey vultures, roadrunners, woodpeckers, hawks, quails, and hummingbirds. The park is home to one threatened bird species, the Mexican spotted owl.
The park's 36 reptile species include desert tortoises, diamondback rattlesnakes (one of the more commonly seen snakes), coral snakes, Gila monsters, short-horned lizards, spiny lizards, and zebra-tailed lizards. Despite the aridity, three amphibian species live in the park. Couch's spadefoot is a species that lives in underground burrows, emerging to breed during summer rains. The other two species are canyon tree frogs and lowland leopard frogs. Forest fires, which make the burned areas more erosion-prone, have destroyed many of the leopard frog's breeding pools, which fill with sediment. The Arizona Game and Fish Department lists the lowland leopard frog as a species of special concern.
Urban sprawl, air and water pollution, noise, light pollution, and a range of habitat restricted by human infrastructure put stress on the park's mammals and other animals, but the most serious immediate threat to them involves roadkill. About 50,000 vertebrates a year die on the park's roads when they are hit by a vehicle. The RMD has few roads, but Picture Rocks Road, an eastâ€"west commuter highway crossing the TMD, is highly dangerous to wildlife. Attempts in 2002 to convert it to a hiking trail failed after the proposal met with stiff public resistance.
Recreation
The park is generally open to hikers all day every day except Christmas; in 2017 the TMD is open to vehicle traffic from sunrise to sunset and the RMD from 7 a.m. to sunset. Both districts have visitor centers, each with park brochures, a bookstore, and other amenities.
More than 165 miles (266Â km) of hiking trails wind through the two districts of the park. The National Park Service (NPS) publishes safety guidelines for these trails, including advice about how to avoid extreme heat, dehydration, flash floods, cactus spines, snakes, cougars, bears, and Africanized bees.
TMD
The TMD has 12 miles (19Â km) of paved roads and 8.5 miles (13.7Â km) of unpaved roads, including the 5-mile (8Â km) Bajada Loop Drive. Trails include the Cactus Garden Trail at the visitor center, the Desert Discovery Nature Trail, and the Valley View Overlook Trail, all easily accessible from Kinney Road or Bajada Loop Drive, and the park has more difficult trails such as the Hugh Norris Trail leading to Wasson Peak. Four of the district's five picnic areas are along park roads, and one is accessible only by trail. No overnight camping is permitted in the TMD.
Hohokam petroglyphs etched into large stones are easily accessible in the TMD. The Signal Hill Trail, which begins at the Signal Hill Picnic Area along the Bajada Loop Drive, leads to an area with dozens of examples of the 800-year-old rock art.
The NPS offers ranger-guided walks and lectures in the TMD in May and June. Starting at the visitor center, the programs cover topics such as "Lizards Are Hot, Lizards Are Cool" and "Cooking with Prickly Pear".
Among the notable artificial structures in the TMD are ramadas, picnic tables, and restrooms built by the Civilian Conservation Corps between 1933 and 1941. Designed to conform to their natural surrounds, the rustic buildings consist mainly of quarried stone and other materials native to the area. Examples include the shelter house at the Ez-Kim-In-Zin Picnic Area and the women's restroom at the Sus Picnic Area.
Bicycling is allowed on the unpaved Bajada Loop Drive and Golden Gate Road, paved roads in the park, and on the half-mile Belmont multi-use trail. It is not allowed on any of the other trails. The visitor center has bicycle racks and water fountains, and but no drinking water is available elsewhere along the biking routes.
Horses and other livestock are allowed on some trails but not others. They are not allowed near the visitor center, or in the Sus or Signal Hill picnic areas. The Cam Boh, El Camino del Cerro, and Sendero Esperanza trailheads have parking places for stock trailers.
RMD
The RMD features the 8.3-mile (13.4 km) Cactus Forest Loop Drive, which provides access to two picnic areas and the central trails. Hiking trails in the RMD are accessible to visitors not only from the Loop Drive but from trailheads near the east ends of two of Tucson's boulevards, Speedway and Broadway. About 7 miles (11 km) south of the RMD visitor center is a trailhead at the north end of Camino Loma Alta. It serves the Hope Camp and Ridge View trails, used by equestrians as well as hikers. It is possible to hike into the RMD from the east via two trailheadsâ€"Miller Creek and Turkey Creekâ€"and from the north via the Italian Spring trailhead, all in the Coronado National Forest outside the RMD boundaries. The United States Forest Service manages these three trailheads and associated trails and the land around them.
Angling across the RMD is the Arizona Trail, which enters the park east of Camino Loma Alta and exits near the RMD's northeast corner. From southwest to northeast, it overlaps the Hope Camp, Quilter, Manning Camp, Mica Mountain, and Italian Spring trails, passes by the Grass Shack and Manning Camp campgrounds and traverses Mica Mountain. The 800-mile (1,300Â km) trail crosses Arizona from its border with Mexico on the south to its border with Utah on the north. Congress named it a National Scenic Trail in 2009. The national trail system is meant to preserve trails with maximum recreation potential and nationally significant scenery.
No Saguaro National Park campgrounds are accessible by road, but the RMD is open to wilderness camping at designated sites along hiking trails. Douglas Spring, Grass Shack, Juniper Basin, Happy Valley Saddle and Spud Rock Spring campgrounds each have three campsites, and Manning Camp Campground has six. The site closest to a road is the Douglas Spring Campground, which requires a hike of about 6 miles (10Â km) each way. A wilderness permit is required for overnight stays.
Livestock such as horses are allowed on some trails but not others, and riding horses off-trail, near the visitor center, or in the picnic areas is prohibited. Horse trailers may be parked only in designated areas within the park or elsewhere outside the park. Livestockâ€"defined by the NPS as horses, mules, or burrosâ€"must carry their own food and are not allowed to graze in the park.
Manning Camp Campground is the main staging area for firefighters, trail-maintenance crews, and scientists working in the RMD. Their supplies are brought in by pack mules that are kept in corrals at the site. Since corral space and water are limited at Manning Camp, a maximum of 10 head of mules or other livestock at a time are allowed to stay overnight. Runoff from a nearby spring, the largest in Rincons, provides water for the livestock.
Bicycling is allowed on the Cactus Forest Loop Drive and two park trailsâ€"the 2.5-mile (4.0 km) multi-use section of the Cactus Forest Trail inside the Loop Drive, and the 2.9-mile (4.7 km) Hope Camp Trail. The visitor center has bicycle racks and water fountains, but no drinking water is available along the biking trails.
On a 40-acre (16Â ha) plot adjacent to the RMD along Broadway, the Desert Research Leaning Center (DRLC) supports scientific and educational projects related to a network of Sonoran Desert parks, including Saguaro National Park. Between 9 a.m. and 4:30 p.m. on weekdays, the DRLC grounds, which include desert plants, an artificial tinaja, and a rainwater collection system, are open to the public. The Sonoran Desert Inventory and Monitoring Network of which the DRLC is part, covers 10 national monuments or parks in Arizona and 1 in New Mexico.
See also
- List of areas in the National Park System of the United States
- Ironwood Forest National Monument
References
Works cited
- Barnes, Will C. (1988). Arizona Place Names. Tucson: The University of Arizona Press. ISBNÂ 978-0-8165-1074-0.Â
- Bezy, John (2005). A Guide to the Geology of Saguaro National Park. Tucson: Arizona Geological Society. ISBNÂ 978-1-892001-22-1.Â
- Dilsaver, Lary M. (March 2015). Joshua Tree National Park: A History of Preserving the Desert (PDF). National Park Service. OCLCÂ 912308073. Retrieved July 9, 2017.Â
- National Park Service (2016). Explore the Waters of Saguaro National Park: A Story Map (Map). National Park Service. Retrieved May 17, 2017 â€" via Esri.Â
External links
- Friends of Saguaro National Park