The Great Plains have a variety of ecosystems because of their large size. Differences in rainfall, elevation, and latitude create different habitats, such as short grass prairies, mixed grass prairies, tallgrass prairies, and riparian areas.
The Great Plains stretch from Mexico in the south through the central United States to central Canada. Many smaller areas exist within this region.
This area is home to many animals, including American bison, pronghorn, mule deer, and white-tailed deer. Birds like ducks, hawks, and sparrows also live there, along with many types of insects and other small creatures.
When people settled in the Great Plains, it caused damage to the environment. Large-scale farming led to the near disappearance of American bison by the late 1800s and reduced the tallgrass prairie to less than 1% of its original size. Today, much of the plains are used for farming and ranching. However, some areas, such as American Prairie in Montana, are working to restore the ecosystem, which is helping the threatened habitat to slowly grow again.
Climate
The climate of the Great Plains is unique because of the many different wind patterns that move across the area, going from east to west and north to south. Since the region is located in the middle of the United States and Canada, many types of air masses pass through, causing weather to change often. This makes the climate of the Great Plains less consistent compared to coastal areas. For example, the western part of the Great Plains is semi-arid, while the eastern part is much wetter. The region experiences all four seasons—summer, autumn, winter, and spring—but each season brings extreme weather conditions. In the southern parts of the region, there are usually 70 to 100 days each year with temperatures above 90 °F, while the northern parts have only 10 to 20 days above 90 °F. These extremes are caused by air masses that come from different directions.
Each type of air mass has different temperature and moisture characteristics. The continental polar air mass brings cold and dry air from central Canada and moves south. The continental tropical air mass comes from the Gulf of Mexico and the Caribbean, bringing hot and dry air as it moves north. The maritime tropical air mass originates from the southwest United States and northern Mexico, bringing warm and moist air, though sometimes it is dry. The maritime polar air mass comes from the Pacific Ocean, moves east over mountain regions, and brings cool, moist air that becomes warm and dry after crossing the mountains. These air masses cause the seasons to have extreme and sudden changes. Winters are often harsh and varied, while midsummer months can bring warm, moist, or dry air depending on the area and the air masses present.
Precipitation patterns also vary across the region. Areas near the Gulf of Mexico receive more than 40 inches of rain each year because of high atmospheric moisture. In contrast, western areas like Montana get less than 14 inches annually. During winter, the southern regions receive less than an inch of snowfall, while northern regions get more than 40 inches. Spring brings heavy precipitation due to interactions between cold, dry air masses and warm, moist air from the Gulf of Mexico, leading to severe thunderstorms, heavy rain, strong winds, hail, and tornadoes. In the Northern Plains, most of the winter season is covered in snow, showing consistent winter precipitation, while summers may have droughts with occasional heavy rains.
Because the climate varies greatly across the Great Plains, changes in climate are not expected to affect all areas equally. For example, dry areas in the south may become drier, while wetter areas in the north may become wetter, increasing the risk of droughts and flooding. The amount of precipitation change depends on future emission scenarios, with higher emissions leading to more extreme conditions. Average annual temperatures are also expected to rise significantly, with winter temperatures already increasing by 7 °F over the past 30 years. These changes could lead to warmer winters, warmer springs, and hotter summers in the south-central plains.
The living communities in the Great Plains may be affected in several ways by these changes. Extreme droughts could harm plants, potentially causing agricultural failures and increasing erosion risk. Loss of soil, nutrients, and moisture could make it difficult for ecosystems to recover and may allow invasive species to take over. Droughts could also dry up prairie potholes, which are important for the breeding of many species, especially migratory waterbirds. Changes in temperature might shift the ranges of some species, leading to competition between species that previously did not share the same area or causing some species to decline or disappear. Earlier springs due to temperature changes could disrupt the timing of biological events, such as when plants bloom or animals reproduce, leading to declines in populations. Other effects may include reduced biodiversity and lower productivity in the region.
Geology, topography, and soil
Originally, large glaciers that formed in Canada moved southward across the central and low-elevation plains in the United States. These glaciers and the materials they left behind greatly changed the land's surface, with the most noticeable changes happening between the Missouri and Ohio Rivers. One important non-living factor that influences the Great Plains is weather, which interacts with the flat, smooth landscape created by glaciers. Low relief topography describes areas with little difference in height. These flat landscapes, such as the grasslands of the Great Plains, affect how rainfall spreads across the region. Rainfall increases from west to east, creating different types of prairie grasslands.
The shape of the land in the Great Plains affects soil composition in areas of different elevations. More soil organic matter is found in lower areas, like grasslands, compared to higher areas, such as buttes, mesas, and escarpments in the northwestern parts of the region. In short grass areas, such as the High Plains, soil typically does not store water because plants rely on whatever moisture is already in the soil during dry periods. This soil is usually dry, made of loam and clay, and supports specialized plants like forbs and shrubs. These plants have adapted with large, complex root systems that make up about 90% of their total plant mass. These roots help the plants stay firmly in the ground and reach moisture deep in the soil. In tall grass prairies, water is more available, and the soil holds more moisture, leading to smaller root systems.
Hydrology
The Great Plains region has many water sources that are important for its water systems. There are thirteen rivers in the Great Plains. Most of these rivers begin in the Rocky Mountain area to the west and are used to water crops on farms. These rivers receive water from melted snow in the mountains, which helps supply water during the growing season. Another water source in the Great Plains is wetlands, which are most common in the northern part of the region that was shaped by glaciers. Up to half of the land in the northern Great Plains is wetlands. These wetlands, along with those in the Nebraska Sandhills, provide important places for migratory birds to live, rest, and raise their young. Playas, or temporary lakes in the southwestern United States, also offer habitats for migratory waterfowl during the winter.
The Ogallala aquifer, also called the High Plains aquifer, is a major source of fresh water for the entire Great Plains region. It provides drinking water to 80% of the population and irrigates 13 million acres of farmland. Water from precipitation, seasonal lakes, and ancient water reserves fills the aquifer, which is located under 174,000 square miles in the Central and Southern regions. The aquifer holds 3.25 billion acre-feet of water and is used by about 200,000 irrigation wells. Around 95% of the water taken from the aquifer is used to water farmland in the Great Plains. Playa lakes, or seasonal lakes, are the main source of water that refills the aquifer, adding about 0.5 inches of water per year to the entire High Plains region. Growth in population, farming, and the economy has increased the need for water in areas that depend on the aquifer. This has caused the average water level in the aquifer to drop by 13 feet since 1950.
Environmental threats
The environmental threats that cause the most harm to the Great Plains include water shortages, land damage, and rising temperatures. Winter temperatures in the Plains have become warmer in recent years, whether in the northern areas near North Dakota or in the southern regions of Texas and nearby states, except during the winters of 2014, 2015, and 2016. Although winters are getting warmer, scientists predict that summer temperatures will rise even more than winter temperatures. This increase in temperature is expected to lead to more frequent extreme weather events, such as heat waves, droughts, and heavy rain. The rise in temperature will also cause water sources in the Great Plains to decrease further. This loss of water will negatively affect all people living in the region. Most of the water used in the Great Plains comes from the High Plains aquifer, also known as the Ogallala aquifer, which covers areas from South Dakota to Texas. Saving water in the Great Plains is one of the most important steps to keep the region sustainable. It is also important for farmers to use the land in ways that protect it. While there are many different methods for sustainable farming, it is difficult to choose the best one. According to the Annals of the Association of American Geographers, farmers are not likely to change their farming methods, which makes the future of the Great Plains uncertain. What is needed are new ways to manage resources, new ideas, and better tools to measure progress. The biggest challenge in improving sustainability in this large region is convincing a large number of farmers to use practices that protect the land. This is difficult because there are so many different farming methods. Prairie conservation requires: 1) new technology to help protect prairie land, 2) efforts to restore native grasslands that have been lost, 3) changes to standard tools used in managing rangelands, and 4) the creation of a new agency to manage natural resources.
Habitats
The Great Plains have many different habitats because of its large size. Factors such as where the area is located on Earth, how high it is above sea level, and how close it is to water sources influence the ecosystems of these grasslands.
Tallgrass prairies are found in the southern and eastern parts of the Great Plains. These prairies once covered 170 million acres in North America. Today, less than 4% remains, mostly in the Kansas Flint Hills. This area is lower in elevation, wetter, and warmer than the High Plains. Some places here receive more than 40 inches of yearly rainfall. Grasses in this region include bluestems and many other species. In the past, many areas of the Midwest that are now forests were once tallgrass prairies. Fire plays an important role in keeping the prairie healthy. Without fire, these areas could turn into forests.
Shortgrass prairies are found in the High Plains of Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. About 70% of the original shortgrass prairie still exists today, making it one of the least fragmented prairie ecosystems.
Characteristic flora
Grasslands are found in areas where there is not enough rain to support trees, so only grasses and a few shrubs can grow there. On the Great Plains, there are three types of grasslands: short grass prairie, mixed grass prairie, and tall grass prairie. In each type, grasses play important roles in the ecosystem. They provide food and shelter, serve as homes for the larvae of many species, and were the main food source for buffalo. These grasses are essential for the environment because they help protect soil from strong winds that blow across the prairie. They are also drought-resistant and have short, strong roots that hold the soil in place.
In the short grass prairie, two main plants are buffalo grass (Bouteloua dactyloides), a tough grass that is a favorite of grazing animals, and blue grama (Bouteloua gracilis), which helps keep soil from eroding. In the tall grass prairie, four main plants grow: big bluestem grass (Andropogon gerardii), Indian grass (Sorghastrum nutans), switchgrass (Panicum virgatum), and little bluestem (Schizachyrium scoparium). Big bluestem grass can grow 4–8 feet tall and was a preferred food source for buffalo.
Characteristic fauna
A "keystone species" is a species that is very important in its community. Keystone species on the Great Plains include the bison and the prairie dog. Many other animals live on the grasslands, such as deer, rabbits, mice, and various types of birds.
In the Great Plains, the prairie dog is a keystone species. Studies comparing the number of species in areas with prairie dogs to areas without them show that prairie dogs greatly affect their environment. They change the types of plants that grow, which influences the habitat and food available for other animals. The prairie dog’s grazing on tall grasses creates a variety of different plant types across the Great Plains. This variety supports many small mammals. In addition to changing plants, prairie dogs build large tunnel systems that other animals, like the desert cottontail, striped skunk, and deer mouse, use for shelter. A key feature of keystone species is their ability to create or change habitats for other animals, and the prairie dog clearly does this.
There are several types of prairie dogs in the region, including black-tailed, white-tailed, and Gunnison’s prairie dogs. The black-tailed prairie dog is the most common and widespread.
The American bison (Bison bison) once lived in huge groups across the Great Plains grasslands. Their population was once in the tens of millions and covered most of North America. However, their numbers have dropped greatly, reducing their impact on the environment. Bison were important grazers, helped convert plants into animal life, and played a key role in recycling nutrients. Their grazing habits helped create the biodiversity seen today in the region, including the prairie dog. Along with fire, bison helped remove extra plant material that built up in the grasslands. Too much dead plant material makes it hard for seeds to grow and limits biodiversity. Removing this extra material helped keep plant diversity healthy. Although bison once played a key role in shaping and keeping the biodiversity of the Great Plains, their much smaller population today has little effect on the region’s ecosystem.
Endangered species
The Indiana bat is an important predator in the Great Plains. It helps keep many different species alive by eating moths, mosquitoes, and flies at night. This bat sleeps in abandoned caves and mines during the winter for hibernation and under tree bark during the warmer months. The Indiana bat is endangered mostly because of human activity in caves. Efforts are being made to protect this species. People are installing gates to stop visitors from entering caves and mines during hibernation. Scientists are also studying other reasons that may be causing the Indiana bat population to decrease.
Another species that is decreasing in number in the Great Plains is the Small White Lady's Slipper. Only 100 of these orchids remain. Invasive plants and human actions have both contributed to the decline of this population, as well as people picking these flowers. The only effective conservation method to help the Small White Lady's Slippers is using controlled burns to remove invasive plants. This allows the orchids to grow with enough space and nutrients to reproduce. The plant needs to grow near a specific type of fungus to survive because of the relationship between the plant and the fungus.