The resilience of an ecosystem relies heavily on the size of its habitats and the diversity of its species. There are few grasslands in the world that better exemplify those attributes than the Nebraska Sandhills. The dunes and valleys across the Sandhills provide a mixture of interconnected habitats that support countless species of plants and animals. A dynamic climate and episodic grazing by cattle provide even more variety. The end result is a globally significant prairie landscape that supports both a thriving ranch culture and an incredible and resilient array of natural communities.
The immensity of the Sandhills prairie supports large and well-connected populations of both plants and animals. As a result, prairie species can withstand episodes of stress from weather, disease, or human management that might be catastrophic in more fragmented landscapes. The Sandhills has plenty to brag about, but the overall magnitude and continuity of its prairie habitat may be its greatest strength.
Each prairie animal and plant species has its own habitat preferences. Some thrive in patches of tall, dense vegetation, others in short vegetation with abundant bare ground, and still others in various intermediate conditions. Because of those varied needs, the number of plant and animal species in a landscape is driven by the variety, or heterogeneity, of its habitats. Again, the Sandhills shine in this regard.
A broad range of topographic features across the Sandhills provides dry upland and moist lowland habitats, as well as warm sun-facing slopes and cool shaded slopes. Layered atop that topographic variation is even more habitat heterogeneity driven by “disturbances,” such as grazing, fire, and drought. Those three forces, and their interactions, are responsible for creating and maintaining prairies across central North America. Patterns of fire and grazing, separately or in combination, regulate the height and density of vegetation, which shapes competitive environments for plants and habitat structure for animals. Those patterns are, and have been for thousands of years, strongly influenced by people and their intentional management of the landscape.
The Sandhills environment has a remarkable ability to maintain productivity during extreme climatic events. The plant species that thrive during years of abundant moisture will fade into the background when drought hits. Those species remain present and ready to reassert themselves when rains return but temporarily cede territory to other plants more adapted to drier soil conditions. As a result, the plant community transforms dramatically as drought enters the scene.
Importantly, that drought-adapted community still includes plants favored by large grazing animals, and the pollen, nectar, seeds, and other essential resources for other wildlife, large and small. The total amount of vegetation produced might decrease during a drought, but the prairie doesn’t simply shut down and forfeit the game. Instead, it changes its lineup and sends a new set of players out onto the field. As a result, while animals might have to alter the specific kinds of plants, nectar, or seeds they eat, they can still find the food and cover they need to survive.
When rainfall picks up again and drought slips away, the plant community again transforms itself. Insect and wildlife communities follow suit. The ability to effectively adapt and respond to changing situations is driven by species diversity, especially by the plants and invertebrates that provide the foundational resources that support larger animals. The bigger the roster, the more options there are for providing an optimal lineup of players at any particular time. In addition to reacting to weather patterns, natural communities in the Sandhills also respond to variable habitat conditions caused by human activities, such as grazing, haying, and fire, each of which shapes habitats in different ways. Many animal species have specific habitat requirements and are found only in places where a certain height or density of vegetation exists. Others are more flexible or have varying habitat needs across seasons. In both cases, the diversity and abundance of animals depends upon a broad spectrum of ever-changing habitat conditions across the Sandhills.
Plants also have conditions in which they are best suited to compete successfully, but they can’t pick up and move when the world changes around them. Instead, plants hunker down during less optimal times and wait for their opportunity to rise again when the time is right. Many plants struggle to compete with the more dominant grasses in the Sandhills prairie and assert themselves only when the canopy of those grasses has been temporarily diminished by something, such as fire or grazing.
When left to grow unimpeded by fire or grazing, prairie vegetation grows relatively tall and dense, dominated by perennial grasses and a selection of wildflowers (forbs) that can successfully compete with those grasses. As time goes on, thatch and litter from previous years’ plant growth accumulates, increasing the density of the habitat even further. Small mammals, like voles, enthusiastically tunnel through that thatch, grouse hide their nests in the tall grasses, and deer and other animals use the thick cover as a place to rest in relative safety.
On the other end of the spectrum, recently burned, hayed, or grazed prairie provides equally valuable resources to a different set of species. Plants that need abundant light try to bloom and reproduce before the big grasses again overtake them. Birds, such as horned larks, upland sandpipers, and long-billed curlews nest in the short vegetation, and a very different wildlife community forms than is found in taller vegetation.
When a site is intensively grazed for several months or more and then allowed to rest, a particularly unique and valuable set of habitat conditions arises. An extended release from perennial grass dominance allows a flush of growth from opportunistic plant species, many of which produce copious amounts of nectar, pollen, and seeds. The structure of the vegetation, consisting of relatively short and sparse grasses and tall well-spaced forbs, provides a perfect place for grouse and their chicks to forage for the abundance of insects fostered by the same architecture. In the absence of grazing, the perennial grasses eventually reclaim their dominance, and the species that thrive in this transitional habitat move on or recede and wait for their next opportunity.
While abhorred by many ranchers, patches of open sand, called “blowouts,” also provide a unique and valuable environment for many species. Plants, such as blowout grass, blowout penstemon, lemon scurf pea, and winged pigweed, thrive in the bare and shifting sands and help stabilize those areas for subsequent colonization by other plants. Distinctive Sandhills animals, like kangaroo rats, earless lizards, sand wasps, and others make their homes in or around these blowouts, and many others use them as places to hunt or bask in the sun.
Interspersed in the Sandhills prairie are patches of shrubs and trees, especially on north-facing dune slopes or along streams and wetlands. These woody plants, streams, and wetlands contain their own communities of plants and animals but also provide important resources for prairie wildlife. On the other hand, some native trees and shrubs, such as smooth sumac and eastern redcedar, are responding to climate change and fire suppression by spreading into prairies at an accelerated rate and threaten to decrease the diversity and resilience of grasslands.
The inherent size and heterogeneity of the Sandhills prairie makes it an incredibly valuable and unique place. Just as humans have helped shape the diversity and resilience of the Sandhills across many centuries, we will play a crucial role in the future. In addition to protecting the intactness of the prairie and water resources of the landscape, it is critically important to provide all the various habitat conditions that support the diversity of life in the Sandhills. As long as the species diversity and large contiguous nature of the prairie persists, its future is bright.