What is a Desert Ecosystem?
While deserts are dry, they can be found all around the world. While we may think of a desert as a hot, dry piece of land, it can be cold as well. Regardless of the region, any desert is usually cold at night and receives very little rainfall. However, they do produce plants, which have adapted to such living conditions.
Several things make up a desert ecosystem. Among those are:
The ecosystem is dependent upon the type of desert; temperate deserts, also referred to as cold deserts, or hot or subtropical deserts. Hot deserts and cold deserts have different kinds of ecosystems. However, despite being very different, the two kinds of deserts have a few similarities.
Similarities of temperate and subtropical deserts:
- Both get fewer than 10 inches of rain annually.
- Dry air is found in both kinds of biomes.
- Both have harsh living conditions that impact people or animals living there.
- Plants have adapted to having less water and harsher temperatures.
- Animals have adapted to the conditions as far as energy, food consumption and when to get out and be active.
In general, deserts are made up of a number of abiotic components – including sand, the lack of moisture, and hot temperatures – basically anything that makes up an ecosystem that isn’t alive. However, there are also a number of biotic factors that affect deserts, which include living things, such as plants and animals.
Antarctica is an example of a temperate desert. The temperatures are actually so cold, they could lead to the death of humans. In order to survive, the animals that live in these kinds of deserts have adapted with the passage of time. The ways they have done this is by adding extra layers of fat, or needing less food and energy in order to survive.
These deserts are too hot for many plants and animals to handle. The animals who call these deserts home have adapted to having less water. Because it is so hot during the day, they have become nocturnal, getting out during the night when it is cooler and easier to maneuver without getting overheated. But, because the nights are cold, they have had to become accustomed to the colder nights. Plants have had to adjust to having less water, so they are sparse and often close to the ground.
Mountains: There are two major factors in the deserts’ creation; mountains’ rain shadows and the large circulation of global winds. As water-filled air is pushed up the mountain slopes, it cools then drops water on that particular side of the mountain. In the event of larger mountain ranges, very little water makes it to the other side. Therefore deserts are often found near mountainous areas, such as:
- The Caucasus Mountains in Asia, where the Karakum and Kyzyl Kum deserts are
- The Atacama Desert, which is partly caused by the Andes Mountains in Chile
- Parts of California, where the Santa Cruz mountains are
- The Sahara desert, which is affected by a number of different mountain ranges
Wind patterns: Global wind patterns, which are complicated, play a significant role in where deserts are located. Winds that circle the globe are the result of the difference between warmer equatorial temperatures as well as the polar temperatures that are cooler. After air has been warmed at the equator, it moves upward. Then it moves toward the north pole and toward the south pole, where it loses moisture, cools off and then sinks before returning to the equator. Therefore, stable wind patterns and shifting global patterns can contribute to where a desert is.
The passage of time greatly influences where and how deserts form. As time has passed, the locations of deserts have moved through the passage of geologic time. This change has been the result of the uplifting of mountain ranges and the continental drift. The horse latitudes are where more deserts are situated, which is generally straddling the Tropic of Capricorn and the Tropic of Cancer, which falls between 15 and 30 degrees to the equator’s north.
There are geologically ancient deserts, such as the Sahara Desert in northern Africa, which is 65 million years old or the Kalahari in central Africa. In North America, three of the four major deserts are within a geological region called the Range Province and the Basin, which falls between the Sierra Nevadas and the Rocky Mountains then extending into the state of Sonora in Mexico.
The forces of erosion thousands of years past shaped the desert landscapes during heavy rainfall. The rocky mountain slopes and hillsides caught the rain, which picked up loose sediment, sand, cobbles and boulders then moved them. As gravity caused the water to be carried downhill, sediment was moved down to the basin. At the bottom of the mountain, the water spread out across a broad area where the mouths of canyons were widened.
The temperature of a given desert will vary due to its geographic location. However, a characteristic of all deserts is the dryness. Heat is reflected by water vapor, which is either in the form of cloud cover or humidity, resulting in a cooling effect. Because of the reactions and the characteristics, deserts experience extreme temperatures, regardless of whether it is heat or cold.
The temperature fluctuations can result in other effects. Cool air sinks and warm air rises, so the fast changes of temperatures cause the air to move fast from one place to another. Because of that, deserts are windy, and those conditions contribute to evaporation. About 90% of available sunlight is transmitted by clear dry air, which in comparison to a typical humid climate seeing 40% of the available sunlight. The additional sunlight has ultraviolet radiation, which can cause major damage to plants, animals and people.
The desert environment has an unpredictable and uneven of the precipitation that is does receive, although that precipitation is minimal in nature. Precipitation amounts can vary from year to year. Some years it may seem as though the desert has gotten more rainfall than usual, but most years have very little rainfall. There can actually be entire years that the desert doesn’t see a drop of rain.
Water is important everywhere and for every living thing. And it is, of course, extremely important in the desert. Because of the lack of water, the plants have made major adaptations.
- The seeds of annual plants stay dormant until a time when there is adequate rainfall available to support a young plant.
- Cacti and other succulent plants store water in their spines, which are residual leaves. The stem is where photosynthesis takes place and the stem has pleats that are able to expand fast when rain falls.
- Evergreens have way cuticles and sunken stomata on shrubs that help hold water and prevent it from escaping. As an example, the holly plant’s leaves are held at 70-degree angles so the sun only hits its sides. When the sun sinks low in the sky, the entire leaf is exposed. A fine salt covering is on the leaves and that helps reflect the sun off of the plant.
More than a fifth of the earth’s land is comprised of deserts. The lack of water can create a survival problem for any humans, animals, plants or organisms. Besides the low rainfall, deserts experience a high amount of water loss from evaporation from the ground and through transpiration of plants. Evapotranspiration is from the combination of evaporation and transpiration. Potential evapotranspiration is how much water that would be lost by transpiration and evaporation if they were possible. Scientists measure this amount under controlled conditions with a large pan of water.
Soil in the desert is known for its coarseness, which permits the little moisture that is in it to pass through quickly, which means it is not as available for plants. Salts accumulate as a result from the high evaporation rate. The soil becomes alkaline and limits plant growth, which is also known as primary productivity.
Because of the entire process required to maintain life in the desert, the impact is that the size of individual animals is limited as well as the size of animal populations. The extremes of heat and aridity result in deserts being one of the most fragile of the ecosystems in the world.
Visitors to the desert should also take the proper precautions to protect themselves as the environment is much different than any other location.
Despite common beliefs that things can’t live in the desert there are a number of creatures that have learned to survive on the distinctive plant life and in the difficult conditions.
- Large mammals like camels make their homes in the desert, and are suited to travel long periods of time without water. Lions live in the deserts of Africa, although they are endangered due to changing weather patterns and the presence of humans.
- Small rodents find homes in the desert, with variations from gerbils to hedgehogs. Larger hyenas and jackals are also often found in deserts.
- Lizards and snakes are particularly suited to the dry, hot climate of the desert, as are amphibious creatures like a number of toads and salamanders.
Image credit: Matthew Paulson , Eric Montfort
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