Great Basin Desert

The Great Basin Desert is a vast, temperate geographical region in the western United States.

It is located between the Sierra Nevada mountains and the Wasatch Range. This desert covers large sections of Nevada and Utah, and extends into eastern California. It is one of the four biologically defined deserts in North America. The region is characterized by a basin and range topography. This means the landscape consists of wide valleys bordered by parallel mountain ranges. These mountains generally run from north to south. The desert is known for its extreme climate. It experiences hot, dry summers and cold, snowy winters. In fact, it is the coldest desert in North America.

The dry climate is caused largely by the rain shadow effect. The Sierra Nevada mountains sit to the west of the desert. As moist air moves in from the Pacific Ocean, it is forced upward by these mountains. This process is called orographic uplift. As the air rises, it loses its moisture as rain and snow on the mountain slopes. By the time the air descends into the Great Basin, it is very dry. This rain shadow effect is much stronger near the Sierra Nevada. Because of this, precipitation levels vary across the desert. The western areas average 10 inches of rain annually, while the eastern areas receive only 4 inches. Additionally, the Rocky Mountains act as a barrier to moisture from the Gulf of Mexico. This helps keep the region arid.

Defining the exact boundaries of the desert is a complex task for scientists. Different organizations use different definitions to describe the region. For example, J. Robert Macey defines the Great Basin scrub desert by the absence of creosote bush. Some valleys, like the Chalfant and Benton valleys, lack this plant. Other areas, such as the Panamint and Saline valleys, do contain it. Mapping these boundaries has changed over time through various studies. In 1987, J.M. Omernik defined the "Northern Basin and Range" ecoregion. In 1999, the U.S. EPA renamed this the "Central Basin and Range." The World Wildlife Fund also uses these ecoregion names. They created the "Great Basin Shrub Steppe" name for certain high-altitude areas. These different labels help researchers track how the land and its species change.

The desert's unique topography creates many different habitat niches. Because the elevation changes so much, the environment changes too. Temperature typically decreases by 3.6 degrees Fahrenheit for every 1,000 feet of elevation gained. This creates massive temperature differences between valley floors and mountain peaks. The biological communities are organized into distinct life zones based on these changes. There are roughly 200 distinct biological communities throughout the region. These communities are grouped into six general life zones. The variation in altitude and soil type allows many isolated populations to develop. This has led to the existence of many genetically unique plant and animal species.

The lowest level is the shadscale zone, located in the valley bottoms. In these areas, mountain runoff evaporates and leaves behind saline, or salty, soils. Some of these parched areas are called playas. On the shores of these playas, the shadscale plant is the dominant species. Other plants like iodine bush and saltgrass also live here. Trees cannot grow in this zone due to the salt and lack of water. Above the shadscale zone, the moisture and soil salinity increase. This leads to the sagebrush zone, which is the largest area in the desert. It covers 38.7 percent of the land and is dominated by big sagebrush. This zone includes lower mountain slopes and alluvial fans.

As you climb even higher, you reach the pinyon-juniper community. This zone is usually found between 5,000 and 8,000 feet. The main plants here are singleleaf pinyon pine and Utah juniper. These trees are short and rarely grow taller than 20 feet. Because of this, scientists often call this area a "pygmy forest." This zone is important because it provides a place for many isolated animals to survive. The trees are spaced far apart, with shrubs and grasses growing underneath. This community relies on increased precipitation and thermal inversions to thrive.

The Great Basin is home to a high level of biological diversity. More than 600 species of vertebrates, or animals with backbones, live in the region. However, many of these species face challenges. Sixty-three species are currently identified as being of conservation concern. This is often because their natural habitats are contracting. Examples include the mountain plover and the kit fox. The environment is also shaped by history. Large Pleistocene lakes, such as Lake Lahontan and Lake Bonneville, once covered parts of the desert. After the last ice age, these lakes dried up. They left behind different levels of salinity and alkalinity in the soil. These ancient lakes continue to influence the desert's ecology today.