page_title: Great Sand Dunes National Park and Preserve
section_title: Ecosystems
hierarchical_section_title: Great Sand Dunes National Park and Preserve / Ecology / Ecosystems
caption_attribution_description: NPS/Patrick Myers
context_page_description: Great Sand Dunes National Park and Preserve is an American national park that conserves an area of large sand dunes up to 750 feet tall on the eastern edge of the San Luis Valley, and an adjacent national preserve in the Sangre de Cristo Range, in south-central Colorado, United States. The park was originally designated Great Sand Dunes National Monument on March 17, 1932, by President Herbert Hoover. The original boundaries protected an area of 35,528 acres. 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. The park encompasses 107,342 acres while the preserve protects an additional 41,686 acres for a total of 149,028 acres. The recreational visitor total was 527,546 in 2019.
  The park contains the tallest sand dunes in North America. The dunes cover an area of about 30 sq mi and are estimated to contain over 1.2 cubic miles of sand. Sediments from the surrounding mountains filled the valley over geologic time periods.
context_section_description: 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. The transition zone between subalpine forest and alpine tundra is an important refuge during storms for some mammals and birds who primarily live on tundra. Bristlecone and limber pines grow at an extremely slow rate, with small statures that belie their true ages as some are more than a thousand years old.
  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.
  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.
  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.
  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.
  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.
caption: Aspens in a riparian zone
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