Great Sand Dunes National Park and Preserve

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Great Sand Dunes National Park and Preserve
IUCN category II ( national park)
Coloradodunes.jpg
Great Sand Dunes
Map showing the location of Great Sand Dunes National Park and Preserve
Map showing the location of Great Sand Dunes National Park and Preserve
Map showing the location of Great Sand Dunes National Park and Preserve
Map showing the location of Great Sand Dunes National Park and Preserve
Location Alamosa and Saguache Counties, Colorado, United States
Nearest city Alamosa
Coordinates 37°43′58″N 105°30′44″W / 37.732870°N 105.512120°W / 37.732870; -105.512120
GREAT SAND DUNES NATIONAL PARK AND PRESERVE Latitude and Longitude:

37°43′58″N 105°30′44″W / 37.732870°N 105.512120°W / 37.732870; -105.512120
Area 149,028 acres (603.09 km2) [1]
Established September 24, 2004 [2]
Visitors 388,308 (in 2016) [3]
Governing body National Park Service
Website Great Sand Dunes National Park and Preserve

Great Sand Dunes National Park and Preserve is a national park that conserves large sand dunes up to 750 feet (229 m) high [4] on the eastern edge of the San Luis Valley, and an adjacent national preserve located in the Sangre de Cristo Range, in southern Colorado, United States. [5] The park was originally proclaimed as Great Sand Dunes National Monument on March 17, 1932. A boundary change and redesignation as a National Park and Preserve was authorized on November 22, 2000 and then established by an act of Congress on September 24, 2004. [2] The park encompasses 107,342 acres (167.7 sq mi) while the preserve protects an additional 41,686 acres (65.1 sq mi) for a total of 149,028 acres (232.9 sq mi). [1]

The park contains the tallest sand dunes in North America. [6] The dunes cover an area of about 30 sq mi (78 km2) and are estimated to contain over 5 billion cubic meters of sand. [7] Sediments from the surrounding mountains filled the valley over geologic time periods. After lakes within the valley receded, exposed sand was blown by the predominant southwest winds toward the Sangre de Cristos, eventually forming the dunefield over an estimated tens of thousands of years. [8] The four primary components of the Great Sand Dunes system are the mountain watershed, the dunefield, the sand sheet, and the sabkha. [7] Ecosystems within the mountain watershed include alpine tundra, subalpine forests, montane woodlands, and riparian zones. [9]

Evidence of human habitation in the San Luis Valley dates back about 11,000 years. The first historic peoples to inhabit the area were the Southern Ute Tribe, while Apaches and Navajo also have cultural connections in the dunes area as well. In the late 17th century, a Spanish governor of Santa Fe de Nuevo México named Don Diego de Vargas became the first recorded European to enter the San Luis Valley. Juan Bautista de Anza, Zebulon Pike, John C. Frémont, and John Gunnison all travelled through and explored parts of the region in the 18th and 19th centuries. The explorers were soon followed by settlers who ranched, farmed and mined in the valley starting in the late 19th century. The park was first established as a national monument in 1932 to protect it from gold mining and the potential of a concrete manufacturing business. [10]

Visitors must walk across the wide and shallow Medano Creek to reach the dunes. The creek typically has a peak flow from late May to early June in most years. In other months, the creek is usually only a few inches deep, if there is any water at all. [11] Hiking is permitted throughout the dunes with the warning that the sand surface temperature may reach 150 °F (66 °C) in the summer. [12] Sandboarding and sandsledding are popular activities in the park and equipment can be rented just outside the park entrance or in Alamosa. [13] Visitors with four-wheel drive vehicles may continue past the end of the park's main road to Medano Pass on 22 miles (35 km) of unpaved road, crossing the stream bed of Medano Creek nine times and traversing 4 miles (6.4 km) of deep sand. [14] Hunting is permitted in the preserve during the months of autumn, while hunting is prohibited within national park boundaries at all times. [15] The preserve encompasses nearly all of the mountainous areas north and east of the dunefield. [5]

History

Park map

The oldest evidence of humans in the area dates back about 11,000 years. Some of the first people to enter the San Luis Valley and the Great Sand Dunes area were nomadic hunter-gatherers whose connection to the area centered around the herds of mammoths and prehistoric bison. They were Stone Age people who hunted with large stone spear or dart points now identified as Clovis and Folsom points. These people only stayed when hunting and plant gathering was good, and avoided the region during times of drought and scarcity. [10]

Modern American Indian tribes were familiar with the area when Spaniards first arrived in the 17th century. The traditional Ute phrase for the Great Sand Dunes is Saa waap maa nache, "sand that moves." Jicarilla Apaches settled in northern New Mexico and called the dunes Sei-anyedi, "it goes up and down." Blanca Peak, just southeast of the dunes, is one of the four sacred mountains of the Navajo, Sisnaajini. These various tribes collected the inner layers of bark from ponderosa pine trees for use as food and medicine. The people from the Tewa/ Tiwa-speaking pueblos along the Rio Grande remember a traditional site of great importance located in the San Luis Valley near the dunes: the lake through which their people emerged into the present world. Sip'ophe, meaning "Sandy Place Lake", is thought to be the springs and/or lakes immediately west of the dunefield. [10]

In 1694, Don Diego de Vargas became the first European known to have entered the San Luis Valley, although herders and hunters from the Spanish colonies in present-day northern New Mexico probably entered the valley as early as 1598. De Vargas and his men saw and hunted a herd of 500 bison, apparently in the southern part of the valley, before returning to Santa Fe. In 1776, Juan Bautista de Anza and an entourage of men and livestock probably passed near the dunes as they returned from a punitive raid against a group of Comanches. At this time, the San Luis Valley was a travel route between the High Plains and Santa Fe for Comanches, Utes, and Spanish soldiers. For some of them, the dunes were likely a visible landmark along the trail. [10]

The first known writings about Great Sand Dunes appear in Zebulon Pike’s journals of 1807. As Lewis and Clark’s expedition was returning east, U.S. Army Lt. Pike was commissioned to explore as far west as the Arkansas and Red Rivers. By the end of November 1806, Pike and his men had reached the site of today’s Pueblo, Colorado. Still pushing southwest, and confused about the location of the Arkansas River, Pike crossed the Sangre de Cristo Mountains just above the Great Sand Dunes. [10]

After marching some miles, we discovered ... at the foot of the White Mountains [today’s Sangre de Cristos] which we were then descending, sandy hills…When we encamped, I ascended one of the largest hills of sand, and with my glass could discover a large river [the Rio Grande] …The sand-hills extended up and down the foot of the White Mountains about 15 miles, and appeared to be about 5 miles in width. Their appearance was exactly that of the sea in a storm, except as to color, not the least sign of vegetation existing thereon.

— Zebulon Pike, January 28th, 1807

In 1848, John C. Frémont was hired to find a railroad route from St. Louis to California. He crossed the Sangre de Cristos into the San Luis Valley in winter, courting disaster but proving that a winter crossing of this range was possible. He was followed in 1853 by Captain John Gunnison of the Corps of Topographical Engineers. Gunnison’s party crossed the dunefield on horseback. [10]

In the years that followed, the Rockies were gradually explored, treaties were signed and broken with resident tribes, and people with widely differing goals flooded into Colorado from the United States and Mexico. In 1852, Fort Massachusetts was built and then relocated to Fort Garland, about 20 miles southeast of the Great Sand Dunes, to safeguard travel for settlers following the explorers into the San Luis Valley. Although many settlers arrived in the San Luis Valley via the trails from Santa Fe or La Veta Pass, several routes over the Sangre de Cristo Mountains into the San Luis Valley were well-known to American Indians and increasingly used by settlers in the late 1800s. Medano Pass, also known as Sand Hill Pass, and Mosca Pass, also called Robidoux’s Pass, offered more direct routes from the growing front-range cities and dropped into the San Luis Valley just east of the Great Sand Dunes. Trails were improved into wagon routes and eventually into rough roads. The Mosca Pass Toll Road was developed in the 1870s, and stages and the mail route used it regularly through about 1911. That year, the western portion was badly damaged in a flash flood. Partially rebuilt at times in the 1930s through the 1950s, it has been repeatedly closed by flooding and is now a trail for hikers. [10]

Medano Creek

The Herard family established a ranch and homestead along Medano Creek in 1875, using the old Medano Pass Road to travel to and from their home. The modern road, open only to 4WD, high clearance vehicles, follows the old route, skirting the dunefield before rising to Medano Pass and continuing east into the Wet Mountain Valley. The Herards grazed and bred livestock in the mountain meadows, built a home, raised horses, cattle, and chickens, and established a trout hatchery in the stream. Other families homesteaded near the dunes as well, including the Teofilo Trujillo family, who raised sheep west of the dunes, and Frank and Virginia Wellington, who built a cabin and hand-dug the irrigation ditch that parallels Wellington Ditch Trail, just south of the park campground. [10]

Gold and silver rushes occurred around the Rockies after 1853, bringing miners by the thousands into the state and stimulating mining businesses that are still in operation. Numerous small strikes occurred in the mountains around the San Luis Valley. People had frequently speculated that gold might be present in the Great Sand Dunes, and local newspapers ran articles in the 1920s estimating its worth at anywhere from 17 cents/ton to $3/ton. Active placer mining operations sprang up along Medano Creek, and in 1932 the Volcanic Mining Company established a gold mill designed to recover gold from the sand. Although minute quantities of gold were recovered, the technique was too labor intensive, the stream too seasonal, and the pay-out too small to support any business for long. [10]

The idea that the dunes could be destroyed by gold mining or concrete manufacturing alarmed residents of Alamosa and Monte Vista. By the 1920s, the dunes had become a source of pride for local people, and a potential source of tourist dollars for local businesses. Members of the P.E.O. Sisterhood sponsored a bill to Congress asking for national monument status for Great Sand Dunes. Widely supported by local people, the bill was signed into law in 1932 by President Herbert Hoover. Similar support in the late 1990s resulted in the monument’s expansion into a national park and preserve in 2000-2004. [10]

Geology

From Star Dune, the tallest dune in the park

The park contains the tallest sand dunes in North America, [6] rising to a maximum height of 750 feet (229 m) [4] from the floor of the San Luis Valley on the western base of the Sangre de Cristo Range. The dunes cover an area of about 30 sq mi (78 km2) and are estimated to contain over 5 billion cubic meters of sand. [7]

Creation of the San Luis Valley began when the Sangre de Cristo Range was uplifted in the rotation of a large tectonic plate. The San Juan Mountains to the west of the valley were created through extended and dramatic volcanic activity. The San Luis Valley encompasses the area between the two mountain ranges and is roughly the size of the state of Connecticut. Sediments from both mountain ranges filled the deep chasm of the valley, along with huge amounts of water from melting glaciers and rain. The presence of larger rocks along Medano Creek at the base of the dunes, elsewhere on the valley floor, and in buried deposits indicates that some of the sediment has been washed down in torrential flash floods. [8]

In 2002, geologists discovered lakebed deposits on hills in the southern part of the valley, confirming theories of a huge lake that once covered much of the San Luis Valley floor. The body of water was named Lake Alamosa after the largest town in the valley. Lake Alamosa suddenly receded after its extreme water pressure broke through volcanic deposits in the southern end of the valley. The water then drained through the Rio Grande, likely forming the steep Rio Grande Gorge near Taos, New Mexico. Smaller lakes still covered the valley floor, including two broad lakes in the northeastern side of the valley. Large amounts of sediment from the volcanic San Juan Mountains continued to wash down into these lakes, along with some sand from the Sangre de Cristo Range. Dramatic natural climate change later significantly reduced these lakes, leaving behind the sand sheet. Remnants of these lakes still exist in the form of sabkha wetlands. [8]

Aerial view of the dunes and the Sangre de Cristo Range

Sand that was left behind after the lakes receded blew with the predominant southwest winds toward a low curve in the Sangre de Cristo Range. The wind funnels toward three mountain passes here—Mosca, Medano, and Music Passes—and the sand accumulates in this natural pocket. The winds blow from the valley floor toward the mountains, but during storms the winds blow back toward the valley. These opposing wind directions cause the dunes to grow vertically. Two mountain streams—Medano and Sand Creeks—also capture sand from the mountain side of the dunefield and carry it around the dunes and back to the valley floor. The creeks then disappear into the sand sheet, and the sand blows back into the dunefield. Barchan and transverse dunes form near these creeks. The combination of opposing winds, a huge supply of sand from the valley floor, and the sand recycling action of the creeks, are all part of the reason that these are the tallest dunes in North America. [8]

Sufficient vegetation has grown on the valley floor that there is little sand blowing into the main dunefield from the valley; however, small parabolic dunes continue to originate in the sand sheet and migrate across grasslands, joining the main dunefield. Some of these migrating dunes become covered by grasses and shrubs and stop migrating. The dunes system is fairly stable as the opposing wind directions balance each other out over time. Also, the main dunefield is moist beneath a thin layer of dry surface sand. While the top few inches of sand are blown around during windstorms, the moist sand remains largely in place. [8]

Scientists estimate that Lake Alamosa disappeared about 440,000 years ago, but the dunes themselves apparently originate from sand deposits from later, smaller lakes. A relatively new dating process, optically stimulated luminescence (OSL), is still in development. This method takes core samples of sand from deep within a dune, and attempts to measure how long quartz grains have been buried in the dark. If the deepest sand deposits can be accurately dated, the age of the dunes could be determined. Samples of sand from deep in the dunes have returned OSL dates varying between a few hundred years to tens of thousands of years old. [8]

The dunes contain dark areas which are deposits of magnetite, a mineral that has eroded out of the Sangre de Cristo Range. This black mineral is composed of iron oxide, so magnets are able to pick it up. Because magnetite is also relatively heavy, the lighter weight sand is blown away on windy days leaving magnetite behind in patches. These black patches can be seen in the dunefield from a distance. [16]

Geography

Map demarcating the national park area (dunefields) and the national preserve (mountains)

Great Sand Dunes National Park and Preserve is located in Saguache and Alamosa Counties, Colorado at approximately 37.75° north latitude and 105.5° west longitude. The national park is located in the San Luis Valley while the national preserve is located to the east in an adjacent section of the Sangre de Cristo Range of the Rocky Mountains. [5] Elevations range from 7,515 ft (2,291 m) in the valley west of the dunes, to 13,604 ft (4,146 m) at the summit of Tijeras Peak in the northern part of the preserve. [17] [9]

The dunes cover an area of about 30 sq mi (78 km2) while the surrounding relatively flat sand sheet which feeds the large dunes is actually the largest component of the entire dunes system, containing about 90% of all the sand in the park. [7] The forested and often snowcapped mountains exceeding 13,000 ft (4,000 m) to the east are the most prominent feature, towering over the high dunes. Other features include snow-fed creeks originating high in the mountains, and several alpine lakes. Two spring-fed creeks in the sand sheet along with a few small lakes in the valley's sabkha section southwest of the dunes create a wetland that nurtures wildlife. [9]

The main dunefield measures roughly 4 mi (6.4 km) east-to-west and 6 mi (9.7 km) north-to-south, with an adjacent 6 sq mi (16 km2) area to the northwest called the Star Dune Complex, for a total of about 30 sq mi (78 km2). The park and preserve together are approximately 15 mi (24 km) east-to-west at the widest point, and approximately 15 mi (24 km) north-to-south, also at the widest point. [5] The park encompasses 107,342 acres (167.7 sq mi), while the preserve protects an additional 41,686 acres (65.1 sq mi) for a total of 149,028 acres (232.9 sq mi). [1]

The Rio Grande National Forest is located to the north and southeast while the remaining forested slopes directly to the east of the dunes were redesignated the Great Sand Dunes National Preserve. The San Isabel National Forest is located to the east of the preserve just beyond the ridge of the Sangre de Cristo Range. Private property abuts most of the southern boundary of the park while the San Luis Lakes State Wildlife Area lies adjacent to the southwestern corner of the park. The Baca National Wildlife Refuge lies to the west and private property of the Baca Grande subdivision of Crestone lies adjacent to the northwest. [5]

The nearest city is Alamosa to the southwest, while the nearest towns are Crestone to the north, Mosca and Hooper to the west, Blanca and Fort Garland to the south, and Gardner to the east. Colorado Springs and Denver are located a few hours away by car to the northeast. [18]

Climate

The Great Sand Dunes are located in the high elevation desert of the San Luis Valley, just west of the Sangre de Cristo Mountains. The summer high temperatures are atypical for a desert area as the average high temperature is only slightly above 80 °F (27 °C) in the warmest month of July; however, the large spread between high and low temperatures is typical of a high desert climate. Low temperatures during winter nights can be extremely cold, with average low temperatures well below 32 °F (0 °C) and record low temperatures below 0 °F (−18 °C) from November through April. Precipitation is very low on the dunes, averaging just 11.13 inches (283 mm) of rainfall per year. The high evaporation rates on the dunes qualify the area as a desert, even though precipitation exceeds 10 inches (250 mm). Snow falls on the dunes as well, but snow melts quickly as the average high temperature is above freezing throughout the year.

Climate data for Great Sand Dunes National Park and Preserve (1950–2006)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 67
(19)
63
(17)
72
(22)
78
(26)
89
(32)
96
(36)
94
(34)
90
(32)
87
(31)
80
(27)
67
(19)
60
(16)
96
(36)
Average high °F (°C) 35.1
(1.7)
39.2
(4)
46.8
(8.2)
56.3
(13.5)
66.2
(19)
76.6
(24.8)
80.8
(27.1)
77.9
(25.5)
71.5
(21.9)
60.5
(15.8)
45.5
(7.5)
36.4
(2.4)
57.7
(14.3)
Daily mean °F (°C) 22.4
(−5.3)
26.5
(−3.1)
33.9
(1.1)
42.1
(5.6)
51.5
(10.8)
60.9
(16.1)
65.6
(18.7)
63.2
(17.3)
56.6
(13.7)
46.1
(7.8)
32.8
(0.4)
23.9
(−4.5)
43.8
(6.6)
Average low °F (°C) 9.8
(−12.3)
13.9
(−10.1)
21.0
(−6.1)
28.0
(−2.2)
36.8
(2.7)
45.2
(7.3)
50.5
(10.3)
48.5
(9.2)
41.7
(5.4)
31.7
(−0.2)
20.1
(−6.6)
11.3
(−11.5)
29.9
(−1.2)
Record low °F (°C) −25
(−32)
−22
(−30)
−9
(−23)
−6
(−21)
15
(−9)
25
(−4)
31
(−1)
33
(1)
22
(−6)
2
(−17)
−12
(−24)
−19
(−28)
−25
(−32)
Average precipitation inches (mm) 0.44
(11.2)
0.37
(9.4)
0.77
(19.6)
0.89
(22.6)
1.09
(27.7)
0.86
(21.8)
1.79
(45.5)
2.00
(50.8)
1.22
(31)
0.86
(21.8)
0.49
(12.4)
0.36
(9.1)
11.13
(282.7)
Average snowfall inches (cm) 6.8
(17.3)
5.3
(13.5)
8.3
(21.1)
5.7
(14.5)
1.4
(3.6)
0
(0)
0
(0)
0
(0)
0.1
(0.3)
2.6
(6.6)
4.7
(11.9)
5.6
(14.2)
40.5
(102.9)
Source #1: https://www.wrcc.dri.edu/cgi-bin/cliGCStT.pl?cogrea (temps) [19]
Source #2: https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?cogrea (precipitation/snowfall) [20]

Ecology

The four primary components of the Great Sand Dunes system are the mountain watershed, the dunefield, the sand sheet, and the sabkha. The mountain watershed receives heavy snow and rain which feeds creeks that flow down from alpine tundra and lakes, through subalpine and montane woodlands, and finally around the main dunefield. Sand that has blown from the valley floor is captured in streams and carried back toward the valley. As creeks disappear into the valley floor, the sand is picked up and carried to the dunefield once again. The recycling action of water and wind, along with a 7% moisture content below the dry surface holding the sand together, contributes to the great height of the dunes. [7]

The dunefield is composed of reversing dunes, transverse dunes—also called crescentic or barchan dunes—and star dunes. The sand sheet is the largest component of the system, comprising sandy grasslands that extend around three sides of the dunefield. Almost 90% of the sand deposit is found in the sand sheet, while the remainder is found in the dunefield. Small parabolic dunes form in the sand sheet and then migrate into the main dunefield. Nabkha dunes form around vegetation. The sabkha forms where sand is seasonally saturated by rising ground water. When the water evaporates away in late summer, minerals similar to baking soda cement sand grains together into a hard, white crust. Areas of sabkha can be found throughout western portions of the sand sheet, wherever the water table meets the surface. Some wetlands in the sabkha are deeper with plentiful plants and animals, while others are shallow and salty. [7]

Flora

Small-flowered sand verbena

There are hundreds of plant species in the park and preserve, adapted for environments as diverse as alpine tundra and warm water wetlands. Trees include aspen, Douglas fir, pinyon pine, ponderosa pine, Rocky Mountain juniper, three-leaf sumac, bristlecone pine, red osier dogwood, and narrow-leaf cottonwood. [21] [22]

Among the flowering plants are alpine phlox, dwarf clover, alpine forget-me-not, fairy primrose, alpine aven, Indian paintbrush, lousewort, blue-purple penstemon, aspen daisy, western paintbrush, elephantella, snow buttercups, scurfpea, Indian ricegrass, blowout grass, prairie sunflower, Rocky Mountain beeplant, rubber rabbitbrush, speargrass, small-flowered sand verbena, narrowleaf yucca, prickly pear cactus, Rocky Mountain iris, and white water buttercup. [21] [22]

Inland saltgrass is the primary type of grass around sabkha wetlands in the park. [21]

Fauna

Elk at Big Spring Creek

Mammals include—from alpine tundra to low elevation grasslands—the pika, yellow-bellied marmot, bighorn sheep, black bear, snowshoe hare, Abert's squirrel, cougar, mule deer, water shrew, beaver, kangaroo rat, badger, pronghorn, and elk. Over 1500 bison are currently ranched within park boundaries on private land owned by The Nature Conservancy which is only open to the public through tours. [23]

Over 200 species of birds are found throughout the park. From higher to lower elevations and dependent on season, some of the bird species include the brown-capped rosy finch, white-tailed ptarmigan, red-breasted nuthatch, peregrine falcon, mountain bluebird, northern pygmy owl, dusky grouse, hummingbird (four species), western tanager, burrowing owl, bald eagle, golden eagle, sandhill crane, American avocet, and great blue heron. [24]

Various reptiles live in the park, such as the short-horned lizard, fence lizard, many-lined skink, bullsnake, and garter snake. [25]

Fish living in the park's streams include the Rio Grande cutthroat trout, Rio Grande sucker, and fathead minnow. [26]

Amphibians include the tiger salamander, chorus frog, northern leopard frog, spadefoot toad, Great Plains toad, and Woodhouse's toad. [27]

The park harbors at least seven endemic insects: the Great Sand Dunes tiger beetle, a circus beetle, Werner's ant-like flower beetle, Triplehorn's ant-like flower beetle, as well as undescribed species of clown beetle, noctuid moth, and robber fly. More than a thousand different kinds of arthropods have been found at the Great Sand Dunes. [28]

Ecosystems

Alpine tundra is the highest elevation ecosystem at Great Sand Dunes where the conditions are too harsh for trees to survive, but wildflowers, pikas, yellow-bellied marmots, ptarmigans, and bighorn sheep thrive. The tundra begins about 11,700 ft (3,600 m) and continues upward to the highest peaks in the park. At subalpine elevations near the tree line grow krummholz (meaning "crooked wood")—trees which are stunted and twisted due to high winds, snow, ice, short growing seasons, and shallow, poorly developed soils. This is a transition zone between subalpine forest and alpine tundra, and an important refuge during storms for some mammals and birds who primarily live on tundra. Because bristlecone and limber pines grow extremely slowly, their small statures often belie true ages with some being over 1000 years old. [9]

Aspens in a riparian zone

Subalpine forests and meadows capture heavy snow in winter and soaking rains in summer. The highest diversity of Rocky Mountain species of plants and animals are found in this ecosystem. Subalpine forest extends from 9,500 ft (2,900 m) to tree line at 11,700 ft (3,600 m). Montane forests and woodlands are found along the drier foothills at approximately 8,000 ft (2,400 m) to 9,500 ft (2,900 m). Pinyon- juniper and ponderosa pine woodlands are found on open, drier slopes, while cottonwood and aspen trees are in drainages. Cougars hunt mule deer here at night. Owls, dusky grouse, turkeys, and bullsnakes all find habitat in these drier, open woodlands. [9]

The riparian zone follows creeks through the subalpine and montane ecosystems at Great Sand Dunes. Cottonwood and aspen trees, red osier dogwood, and alder grow well in this wet environment, in turn providing shade and habitat for black bears, water shrews, and western tanagers. Rio Grande cutthroat trout are found in Medano Creek. [9]

While the top few inches of the dunefield are often dry, the dunes are moist year-round due to ongoing precipitation. Moisture content of 7% beneath the surface sand allows species such as Ord's kangaroo rat, Great Sand Dunes tiger beetle, scurfpea, and blowout grass to survive here. Many animals visit the dunes from other habitats, including elk, pronghorn, bison, coyotes, bobcats, and raptors. [9]

Sandhill cranes in wetland

The sand sheet includes extensive grasslands and shrublands that surround the dunefield on three sides, from 7,500 ft (2,300 m) to 8,200 ft (2,500 m). The sand sheet varies from wet meadows to cool-grass prairie to desert shrubland, depending on proximity to groundwater and soil type. Elk and pronghorn are common, while burrowing owls nest in the ground and other raptors float through the skies searching for mice, kangaroo rats, and short-horned lizards. [9]

The sabkha is a wetland region where groundwater rises and falls seasonally, leaving white alkali deposits on the surface. Inland saltgrass is common in this area. Toads can reproduce in sabkha wetlands when they are seasonally filled with sufficient fresh water. Shore birds such as the American avocet hunt tadpoles and insects in the shallow water. Wetlands speckle the San Luis Valley and are important habitat for sandhill cranes, shore birds, amphibians, dragonflies, and freshwater shrimp. Grassland species such as elk also use these waters for drinking. The sabkha and wetlands are at approximately 7,500 ft (2,300 m) in elevation. [9]

Features

Upper Sand Creek Lake and Basin from Marble Mountain

The park preserves the tallest sand dunes in North America, [6] as well as alpine lakes and tundra, mountain peaks over 13,000 feet (3,962 m) in elevation, mixed conifer forests, grasslands, and wetlands. [29]

Medano Creek, which borders the east side of the dunes, never finds a permanent and stable streambed as fresh sand falls in the creek. Small underwater sand ridges that act like dams form and break down, creating surges of water which resemble waves. The surges occur at an average interval of about 20 seconds. In a high-water year, the surges can be as high as 20 in (51 cm). The "surge flow" mainly occurs during the peak flow period from late May to early June in most years. [11]

Big Spring Creek is a unique spring-fed creek formed by an unconfined aquifer which creates wetlands that support rare species and plant communities in a generally arid area. The creek was designated a National Natural Landmark in 2012. [30]

Recreation

Sandboarding

Accessing the dunes requires walking across the wide and shallow Medano Creek. The creek typically flows past the main dunes parking area from late April through late June, with peak flow occurring from late May to early June in most years. In other months, the creek is usually only a few inches deep, if there is any water at all. [11] Hiking is permitted throughout the dunes, with the warning that the sand can get very hot in the summer, up to 150 °F (66 °C). [12] Sand wheelchairs are available at the visitor center. [31] Sandboards and sand sleds can be rented just outside the park entrance or in Alamosa which is the closest city. [13]

Mosca Pass Trail is a 7 mi (11 km) roundtrip hike that follows a small creek through aspen and evergreen forests to Mosca Pass—elevation 9,737 ft (2,968 m) [5]—in the Sangre de Cristo mountains. American Indians and early settlers used this route for travel between the San Luis Valley and the Wet Mountain Valley to the east. Several trails located in the northeastern section of the park lead to alpine lakes high in the mountains. A trail to Medano Lake and the summit of Mount Herard is located off Medano Pass Road. A trail along Sand Creek leads to the Sand Creek Lakes and Music Pass—elevation 11,380 ft (3,470 m) [5]—with a view of the Upper Sand Creek basin. Spur trails along Sand Creek lead to the four alpine lakes which feed the creek, and to several 13,000 ft (4,000 m) peaks above the basin. The Sand Ramp Trail traverses between the dunefield and the mountains, connecting the park's campground to Medano Pass Road (follow the road up to Medano Lake and Pass), as well as the base of the Sand Creek Trail. [12] [5] Most of the park's grasslands, shrublands and wetlands have no established trails but are generally open to hiking. The Nature Conservancy's Medano Ranch property may only be visited on a guided tour. A fence surrounds the property to contain the Conservancy's bison herd and demarcate the boundaries. [32]

Medano Pass Road is a 22 mi (35 km) four-wheel drive (4WD) road that begins where the main park road ends. [33] The unpaved road crosses Medano Creek nine times and traverses 4 mi (6.4 km) of deep sand. Only street-licensed 4WD motor vehicles or motorcycles, and bicycles are permitted. [14] Fat tire bikes are the only type of bicycle recommended by the park service due to the deep sandy stretches. [34] The road winds around the eastern side of the dunefield, up through a forested mountain canyon inside the National Preserve, and then over Medano Pass—elevation 9,982 ft (3,043 m) [5]—at the 11.2 mi (18.0 km) mark. The road then continues down into the Wet Mountain Valley and connects with Colorado State Highway 69. Travellers are advised that hunting is permitted in the National Preserve during the months of autumn. [14]

Unlike all other national parks in the contiguous United States, Great Sand Dunes National Park includes a preserve which allows hunting. [15] Sport hunting has regulations which include not pursuing a wounded animal if it enters the park and not hunting inside national park boundaries. Mountain lion hunting with dogs is also allowed in the preserve, but unless the dogs have spotted the lion and are pursuing it, they are required to be leashed. [35] Other game species include turkey, bear, bighorn sheep, elk and mule deer. [36]

Designations

The Great Sand Dunes was initially designated a National Monument which combined various types of protected areas to satisfy the objectives of the National Park Service, the Nature Conservancy and other organizations, and to combine conservation and sustainable use of the ecosystem. The result was similar to the protected area mosaic recommended in the early 1980s for parts of the Yukon in Canada. Implementation was staged, with many interactions and adaptations over time. [37]

The dunes and surrounding area were designated a National Monument in 1932 after a bill—sponsored by the P.E.O. Sisterhood and widely supported by local residents—was signed into law by President Herbert Hoover. Similar support in the late 1990s resulted in the monument’s re-designation as a National Park and Preserve in 2000-2004. [10]

With the help of the Nature Conservancy, the federal government purchased 100,000 acres (40,469 ha) of the Baca Ranch, which in effect tripled the size of the park. The land purchased was split into three sections. Part of the Sangre de Cristo Mountains would be transferred to the Rio Grande National Forest, another section to the west would be set aside as a wildlife area and would host a wild bison herd and the last section to the east would be transferred from the Rio Grande National Forest and would be designated as a National Preserve open to regulated seasonal hunting. [38]

Wide view of the dunes with people at right in foreground

GREAT SAND DUNES NATIONAL PARK AND PRESERVE INFORMATION

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