Nebraska Sand Hills Desert

• Category: Grassland, Tundra, and Human Biomes.
• Geographic Location: North America.
• Summary: A largely intact native temperate grassland habitat that features wetlands and small lakes scattered throughout a mixed-grass prairie ecosystem.

Located almost entirely within the state of Nebraska, near the geographic center of the United States, the Sand Hills Desert biome encompasses one of the largest sand dune formations in the Western Hemisphere. It also is one of the largest contiguous and least-disturbed prairies, and among the largest and most complex wetland ecosystems in the United States. It faces several environmental challenges, such as the overgrazing of cattle, expansion of agriculture, climate change, and drought.

The Nebraska Sand Hills Desert is a relatively stable, mostly intact ecoregion that spans the Great Plains region and High Plains subregion; it covers about one quarter of the state of Nebraska. The Sand Hills have a more intact natural habitat—about 80 percent—than most other grasslands in the Great Plains and throughout the world. This is due primarily to the absence of agriculture, as very little of the Sand Hills has been plowed.

The Sand Hills are classified as a semiarid region, with average annual rainfall from 23 inches (580 millimeters) in the east, to less than 17 inches (430 millimeters) in the west. Temperatures range from -30F (-34C) in winter to 100F (38C) in summer.

The Sandy Formations

One of the smallest of the Great Plains ecoregions, the Sand Hills represents a relatively stable and intact biome of mixed grasslands covering an area variously defined as 19,600 or 23,600 square miles (50,764 or 61,124 square kilometers). Its topography is characterized by mixed-grass and tallgrass prairie, and a wide variety of sand formations, most prominently sand dunes, some of which are stabilized by vegetation. Some of the dunes can reach heights of 340–400 feet (104–122 meters) and stretch up to 2 miles (3 kilometers) in length.

Other formations include blowouts—holes in the surface of the sand created by rapid wind erosion that can reach several hundred feet (meters) in diameter—and widely spaced barchans, which are arc-shaped ridges of sand with downwind-pointing “horns.” The average elevation of the region increases gradually from 1,800 feet (549 meters) in the east to 3,600 feet (1,097 meters) in the west.

The Sand Hills sit atop the vast Ogallala Aquifer, one of the world’s largest aquifers. When the water table of the massive but shallow Ogallala, also known as the High Plains Aquifer, rises above interdunal valleys, then wetlands, small ponds, or shallow lakes are formed, with a typically average area of approximately 10 acres (4 hectares). These can be seen scattered throughout the dry and sandy grassland dunes in the western and northern regions.

Creeks, rivers, and subirrigated meadows also are nourished by Ogallala’s precipitation-charged groundwater, giving rise to rich and varied vegetation that provides ideal grazing ground for both wild ruminants and farm-raised cattle. The western part of the Sand Hills is drained by small interior drainage basins, while the eastern and central areas are drained by tributaries of the Niobrara and Loup Rivers. The Snake and Dismal Rivers also run through the region.

The sands are generally stabilized by the root systems of local vegetation spread throughout the sandy soil, comprised primarily of entisols, the second-most abundant soil order in the world after inceptisols. The Sand Hills represent the most intact natural and continuous habitat of all the ecoregions in the Great Plains, supporting a diverse and extensive array of flora and fauna.

Flora

While the Sand Hills ecoregion falls into the mixed-grass prairie classification, its singular landscape of dry and sandy upland dunes interspersed with thousands of lakes and wetlands becomes a biodiverse community of sand-tolerant vegetation from various prairie types. These include some species found in northern boreal forest ecosystems. Consequently, the Sand Hills are considered a distinct grassland association, supporting around 720 species of plants, the majority of which are native. Only about 7 percent of Sand Hills flora are nonnative species. Half of them are found in most other prairie ecoregions, due in part to the difficulty that foreign plant species have in negotiating the sandy soil.

While supporting a variety of short-grass, mixed-grass, and tallgrass species, the Sand Hills are dominated by a few hardy perennial monocots that are good for grazing wildlife and cattle, such as sand bluestem (Andropogon hallii), a bunchgrass known as turkey-foot that is high in crude protein and ideal for sandy-soil stabilization; prairie sandreed (Calamovilfa longifolia), an abundant, drought-tolerant, warm-season tallgrass, the seeds of which feed songbirds and rodents; and needle-and-thread (Stipa comata), a cold-winter bunchgrass that provides excellent forage in the fall and winter months. Another species that thrives in blowouts is the sandhill muhly (Muhlenbergia pungens), a drought-tolerant bunchgrass well adapted to coarse-textured soil.

Found only in the Sand Hills and central Wyoming, the endangered Hayden’s penstemon (Penstemon haydenii), a stout perennial flowering herb, has adapted to survive within blowouts. Hence, it is also known as blowout penstemon, and it stabilizes the sandy soil. However, penstemon dies off when other species begin to recolonize the newly stabilized surface and off-road vehicle use destroys many of the plants. It may take years for a blowout to return to its original stabilized state.

Additionally, ranchers are generally careful not to let cattle overgraze, fearing that a reduction of vegetation will lead to more blowouts. The prevention of naturally occurring fires has led to fewer blowouts. Such land management practices have increased the frequency of many prairie plants and significantly reduced the habitat of the Hayden’s penstemon. Other plants in the area have been listed as threatened, such as the western prairie fringed orchid (Platanthera leucophaea).

Fauna

The sandy-bottomed ponds, lakes, rivers, and streams that exists throughout the Sand Hills provide an ample freshwater source for wildlife and cattle, and also support many fish species. Some of the lakes are alkaline, and support several phyllopod shrimp species.

Game fish, primarily yellow perch, northern pike, largemouth bass, bluegill, and carp, were introduced into many lakes in the Sand Hills, and trout was added to a number of coldwater streams. In addition, there are 27 species of amphibians and reptiles in the region, including one salamander, three toads, four each of frogs and lizards, six turtles, and nine snakes.

The Nebraska Sand Hills Desert biome supports numerous insect species, including spiders, dragonflies, grasshoppers, and mosquitoes, the populations of which increase during the summer when bodies of still water increase across the region.

Limited human development and sprawling virgin prairie make this ecoregion a long-term stable habitat for varieties of animals, and an important habitat for more than 300 vertebrate species. Birds including waterfowl, shorebirds, songbirds, and birds of prey are particularly well represented in this area. Because of urban and agricultural development elsewhere in United States, the Sand Hills ecoregion has increased in importance as a last refuge for some bird populations.

The natural range of the greater prairie chicken (Tympanuchus cupido), a large bird in the grouse family, for instance, has been decreasing across central North America. Its territory has been impacted by human expansion, primarily agricultural development, and the prairie chicken has become endangered or extinct in some parts. Consequently, the species is listed as Largely Depleted by the International Union for Conservation of Nature (IUCN). Though conservation efforts have been underway for some time, according to the IUCN, the population of the prarie chicken is so depleted that even if efforts continue, it is highly unlikely that the species will ever fully recover.

The ponds and lakes of the Sand Hills provide temporary refuge for several migratory bids, including ducks, geese, and cranes. The Sand Hills sit along the Central Flyway, a bird migration route connecting Canada and Mexico through the Great Plains. Favored because of its lack of mountains, ample refuge, availability of food, and freshwater sources, the Central Flyway is used by some migratory birds traveling from the Arctic Circle to the southern tip of South America.

Birds that make the Sand Hills their primary habitat include the wild turkey and Nebraska’s state bird, the western meadowlark (Sturnella neglecta), a ground-foraging icterid. Some of the many other birds that rely on the Sand Hills ecoregion include hunting birds such as Swainson’s hawk (Buteo swainsoni) and burrowing owl (Athene cunicularia); shorebirds such as the upland sandpiper (Bartramia longicauda), long-billed curlew (Numenius americanus), and willet (Catoptrophorus semipalmatus); and seabirds such as the trumpeter swan (Cygnus buccinator), American white pelican (Pelecanus erythrorhynchos), and double-crested cormorant (Phalacrocorax auritus).

Also featured here are turkey vulture (Cathartes aura), sharp-tailed grouse (Tympanuchus phasianellus), barn swallow (Hirundo rustica), great crested flycatcher (Myiarchus crinitus), horned lark (Eremophila alpestris), loggerhead shrike (Lanius ludovicianus), western kingbird (Tyrannus verticalis), eastern kingbird (T. tyrannus), common nighthawk (Chordeiles minor), and lark sparrow (Chondestes grammacus).

Native mammalian species represented in the Nebraska Sand Hills include pronghorn antelopes, mule deer, white-tail deer, coyotes, red foxes, ground squirrels, bats, kangaroo rats, and porcupines.

The millions of wild bison that once roamed the Sand Hills have been replaced by more than 530,000 cattle. Today, one of America’s largest bison herds lives on protected land at the Nature Conservancy’s Niobrara Valley Preserve. Elk, which once roamed freely, are now found only at the Fort Niobrara Wildlife Refuge. Other protected areas include Valentine National Wildlife Refuge and Crescent Lake.

Environmental Threats

Environmental challenges to the Nebraska Sand Hills Desert biome are related primarily to human activity and include overgrazing by cattle, prevention of naturally occurring brush fires, and the development of agriculture using center-pivot irrigation methods.

Invasive species also are a threat, from the carp that have degraded many lakes, wetlands, and streams to the purple loosestrife and reed canary grass that threaten riparian areas and wetlands. The musk thistle and leafy spurge are negatively impacting prairie communities, as are Eastern red cedars.

Other concerns include interbasin water transfers that lower the water table, impact wetlands, and reduce flows in streams and rivers, as well as oil pipeline construction that could pollute the Ogallala Aquifer. According to Rheinhardt Scholtz, a postdoctoral associate of the University of Nebraska, the grasslands are the most threatened and the least conserved and protected areas. Climate change poses a challenge to this desert biome, as warming average temperatures may make the grasslands here more unstable, increasing the chance of fires, mild drought, and erosion.

Bibliography

BirdLife International. "Tympanuchus cupido." The IUCN Red List of Threatened Species, 2020. dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T22679514A177901079.en. Accessed on 13 Nov. 2024.

Bleed, Ann. An Atlas of the Sand Hills. University of Nebraska at Lincoln, 1990.

Jones, Stephen. The Last Prairie. Ragged Mountain Press, McGraw-Hill, 2000.

Noss, Reed. “Nebraska Sand Hills Mixed Grasslands.” One Earth, www.oneearth.org/ecoregions/nebraska-sand-hills-mixed-grasslands/. Accessed 12 Nov. 2024.

Ricketts, Taylor H., et al. Terrestrial Ecoregions of North America: A Conservation Assessment. Island Press, 1999.

Scholtz, Rheinhardt, and Dirac Twidwell. "The Last Continuous Grasslands on Earth: Identification and Conservation Importance." Conservation Science and Practice, vol. 4, no. 3, 2022, p. e626. doi.org/10.1111/csp2.626. Accessed 13 Nov. 2024.

Schrage, Scott. “Nebraska Sandhills Rated as World's Most Intact Prairie.” Nebraska Today, 28 Feb. 2022, news.unl.edu/article/nebraska-sandhills-rated-as-world-s-most-intact-prairie. Accessed 12 Nov. 2024.

Vinton, Mary Ann, and Alexander Larsen. "Landscape Variability Underpinning the Social-Ecological System in the Nebraska Sandhills." Great Plains Research, vol. 32, no. 1, 2022, pp. 69-81. DOI: 10.1353/gpr.2022.0005. Accessed 2 Sept. 2022.