Plants grow, bloom, produce new seeds, and die, often in a short span of time. A soaking rain can change a desert into a wonderland of flowers almost overnight.
Animals that have adapted to a desert environment are called xerocole s. Xerocoles include species of insects, reptiles, birds, and mammals. Some xerocoles avoid the sun by resting in scarce shade. Many escape the heat in cool burrow s they dig in the ground. The fennec fox, for example, is native to the Sahara Desert. Fennec fox communities work together to dig large burrows, some as large as 93 square meters 1, square feet.
Dew can collect in these burrows, providing the foxes with fresh water. However, fennec foxes have adapted so they do not have to drink water at all: Their kidney s retain enough water from the food they eat. Most xerocoles are nocturnal. They sleep through the hot days and do their hunting and foraging at night.
Deserts that seem desolate during the day are very active in the cool nighttime air. Foxes, coyotes, rats, and rabbits are all nocturnal desert mammals. Snakes and lizards are familiar desert reptiles. Insects such as moths and flies are abundant in the desert. Most desert birds are restricted to areas near water, such as river banks.
However, some birds, such as the roadrunner, have adapted to life in the desert. The roadrunner, native to the deserts of North America, obtains water from its food.
Some xerocoles have bodies that help them handle the heat. Some desert vultures urinate on their own legs, cooling them by evaporation. Many desert animals have developed ingenious ways of getting the water they need. The thorny devil, a lizard that lives in the Australian Outback , has a system of tiny grooves and channels on its body that lead to its mouth. The lizard catches rain and dew in these grooves and sucks them into its mouth by gulping.
Camels are very efficient water users. The animals do not store water in their humps, as people once believed. The humps store fat. Hydrogen molecule s in the fat combine with inhaled oxygen to form water. During a shortage of food or water, camels draw upon this fat for nutrition and moisture.
Dromedary camels, native to the Arabian and Sahara deserts, can lose up to 30 percent of their body weight without harm. People and the Desert About 1 billion people live in deserts. Many of these people rely on centuries-old customs to make their lives as comfortable as possible Civilization s throughout the Middle East and Maghreb have adapted their clothing to the hot, dry conditions of the Sahara and Arabian deserts. Clothing is versatile and based on robes made of rectangles of fabric.
Long-sleeved, full-length, and often white, these robes shield all but the head and hands from the wind, sand, heat, and cold.
White reflects sunlight, and the loose fit allows cooling air to flow across the skin. These robes of loose cloth can be adjusted folded for length, sleeves, and pockets, depending on the wearer and the climate. A thobe is a full-length, long-sleeved white robe. An abaya is a sleeveless cloak that protects the wearer from dust and heat.
A djebba is a short, square pullover shirt worn by men. A kaffiyeh is a rectangular piece of cloth folded loosely around the head to protect the wearer from sun exposure, dust, and sand.
It can be folded and unfolded to cover the mouth, nose, and eyes. Kaffiyehs are secured around the head with a cord called an agal. A turban is similar to a kaffiyeh, but wrapped around the head instead of being secured with an agal. Turbans are also much longer—up to six meters 20 feet! Desert dwellers have also adapted their shelters for the unique climate. The ancient Anasazi peoples of the southwestern United States and northern Mexico constructed huge apartment complexes in the rocky cliff s of the Sonoran Desert.
These cliff dwellings, sometimes dozens of meters off the ground, were constructed with thick, earthen walls that provided insulation. Although temperatures outside varied greatly from day to night, temperatures inside did not. Tiny, high windows let in only a little light and helped keep out dust and sand. The need to find food and water has led many desert civilizations to become nomadic.
Nomadic cultures are those that do not have permanent settlements. In the deserts of the Middle East and Asia, nomadic tent communities continue to flourish. Tent walls are made of thick, sturdy cloth that can keep out sand and dust, but also allow cool breezes to blow through. Tents can be rolled up and transported on pack animal s usually horses, donkeys, or camels.
Nomad s move frequently so their flocks of sheep and goats will have water and grazing land. Besides animals like camels and goats, a variety of desert vegetation is found in oases and along the shores of rivers and lakes. Figs, olives, and oranges thrive in desert oases and have been harvested for centuries. Some desert areas rely on resource s brought from more fertile areas—food trucked in from distant farmlands or, more frequently, water piped from wetter regions.
Large areas of desert soil are irrigate d by water pumped from underground sources or brought by canal from distant rivers or lakes. The booming Inland Empire of southeastern California is made up of deserts the Mojave and the Sonoran that rely on water for agriculture, industry, and residential development.
Canal s and aqueduct s supply the Inland Empire with water from the Colorado River, to the east, and the Sierra Nevada snowmelt to the north.
A variety of crops can thrive in these irrigated oases. Sugar cane is a very water-intensive crop mostly harvested in tropical regions. However, sugar cane is also harvested in the deserts of Pakistan and Australia.
Water for irrigation is transported from hundreds of kilometers away, or drilled from hundreds of meters underground. Oases in desert climates have been popular spots for tourists for centuries. The Dead Sea has had flourishing spas since the time of King David. Air transportation and the development of air conditioning have made the sunny climate of deserts even more accessible and attractive to people from colder regions. Desert parks, such as Death Valley National Park, California, attract thousands of visitors every year.
But in cities, structures like buildings, roads, and parking lots hold on to daytime heat long after the sun sets. This is called the urban heat island effect. It is less pronounced in desert cities than cities built in heavily forested areas.
New York was built on wetland habitat, and Atlanta was built in a wooded area. They may be only slightly warmer than the surrounding desert. Deserts can hold economically valuable resources that drive civilizations and economies. The most notable desert resource in the world is the massive oil reserve s in the Arabian Desert of the Middle East. More than half of the proven oil reserves in the world lie beneath the sands of the Arabian Desert, mostly in Saudi Arabia.
The oil industry draws companies, migrant workers, engineers, geologist s, and biologist s to the Middle East. Desertification Desertification is the process of productive cropland turning into non-productive, desert-like environments. Desertification usually happens in semi-arid areas that border deserts. Human activities are a primary cause of desertification.
These activities include overgrazing of livestock , deforestation , overcultivation of farmland, and poor irrigation practices. Overgrazing and deforestation remove plants that anchor the soil.
As a result, wind and water erode the nutrient -rich topsoil. Hooves from grazing livestock compact the soil, preventing it from absorbing water and fertilizer s. Agricultural production is devastate d, and the economy of a region suffers.
The deserts of Patagonia , the largest in South America, are expanding due to desertification. Patagonia is a major agricultural region where non-native species such as cattle and sheep graze on grassland.
Sheep and cattle have reduced the native vegetation in Patagonia, causing loss of valuable topsoil. More than 30 percent of the grasslands of Argentina, Chile, and Bolivia are faced with desertification. People often overuse natural resources to survive and profit in the short term, while neglecting long-term sustainability. Madagascar, for instance, is a tropical island in the Indian Ocean. Seeking greater economic opportunities, farmers in Madagascar engaged in slash-and-burn agriculture.
This method relies on cutting and burning forests to create fields for crops. Some of the crescent-shaped dunes in this Viking image of Mars are more than a kilometer wide. The dark material that streaks from the horn-shaped features may be dust recently blown from the dunes courtesy of NASA. The trade winds in two belts on the equatorial sides of the Horse Latitudes heat up as they move toward the Equator. These dry winds dissipate cloud cover, allowing more sunlight to heat the land.
Most of the major deserts of the world lie in areas crossed by the trade winds. The Sahara of Africa is the world's largest desert. It contains complex linear dunes that are separated by almost 6 kilometers. Skylab photograph. These deserts are in interior drainage basins far from oceans and have a wide range of annual temperatures. The Sonoran Desert of southwestern North America is a typical midlatitude desert. A rare rain in the Tengger, a midlatitude desert of China, exposes ripples and a small blowout on the left.
Winds will shortly cover or remove these features. As there is no water vapor in the air reaching these locations, deserts form. Once again, the air above these deserts is heated, unhindered, by the sun, resulting in the high daytime temperatures. Heat then rapidly escapes into the atmosphere at night, accounting for the low nighttime temperatures. What can occur are advection fogs, which form when the cold ocean air encounters warm land surfaces.
Some deserts are located right next to snowy mountain ranges. This is because, in these areas, the mountains create what is known as rain shadows. Sub-tropical trade winds, which originate from the North-East northern hemisphere or South-East southern hemisphere , are blocked by any mountain ranges in their path. The air is pushed up over the mountains, but as the air rises, its temperature decreases. The air holds less moisture at these lower temperatures, and so precipitation occurs over the mountain.
By the time the air arrives on the other side of the mountain always the western side because of where the trade winds originate , it is dry, resulting in the formation of deserts in these rain shadows. Deserts can form in regions that are so far from the coast that no moisture remains in the air when it reaches these locations.
Antarctica is considered to be a desert, even though it is covered in snow and not sand. This is because these areas still experience extremely low levels of precipitation. Because the air here is so cold, it holds very little moisture. Any moisture it does hold will be precipitated again as snow. The low temperatures also prevent the fallen snow from melting and being evaporated in any significant quantity, so the snow just builds up.
Desertification is the process whereby non-desert land is transformed into deserts. The cause of desertification is a combination of three factors:.
These three factors cause a loss of protective vegetation covering the land, exposing the soil to the effects of wind and rain, increasing the rate of evaporation from the grounds, and increasing the risk of weathering soil erosion. As our climate changes, it is showing a downward trend in the amount and reliability of rainfall. This means that the occurrence and intensity of periods of drought increase.
Bodies of water, from rivers to waterholes, dry up during these rainless periods. Loss of surface water and precipitation means that vegetation cover dies, leading to desertification. Furthermore, global warming causes a global rise in temperatures. As air temperatures rise, the rate of evaporation increases, but the rate of condensation decreases, and less rain falls. Once again, this contributes to the death of vegetation and the loss of protective ground covering. The land can only support a certain number of grazing animals.
This number depends on the amount of vegetation, the rate at which the vegetation regrows, the time the land is allowed to recover, the number of animals per area, etc.
As people increase their livestock numbers, there are more individual animals grazing on smaller portions of land. Furthermore, the increase means that there is no chance to rotate the grazing areas, and the land is not allowed time to recover. This is known as overgrazing. It not only removes the vegetation cover but is also strips the soils of its nutrients, which means that vegetation cannot regrow, even if given a chance to do so, leading to desertification.
As there are more mouths to feed, farmers have to expand their farmlands, which involves pulling up natural vegetation to plant crops. Additionally, farmers have to increase the frequency at which each pasture is used, which means the land has less time to recover and it becomes infertile.
More people also require more livestock, so it contributes to more animals being on the land. Yet another result of increased human populations is the increased need for wood, which leads to deforestation, which also contributes to desertification. The Sahara Desert is always going to be one of the first deserts that people think of; this is because it holds the title of the largest desert in the world.
All coastal plants have thick, fleshy leaves that grab available water and store it for future use. In some plants, the surfaces are tightly ridged and grooved. When it rains, the stem bulges and grooves flatten to store water. As the water is used, the stem shrinks slowly back to its tight form. Coastal desert plants include the salt bush, buckwheat bush, rice grass, and black sage. Dry climates force some types of toads to seal themselves in burrows and remain inactive for up to nine months.
When a heavy rain comes along, soaking the earth, they get moving again. Some insects lay eggs that stay dormant for long periods, until the environment is suitable for hatching. Other coastal desert animals include, insects, coyotes, rabbits, toads, owls, eagles, lizards, and snakes.
Rain shadow deserts are formed when tall mountain ranges stop moisture-rich clouds from reaching areas on the far protected side of the mountains. These deserts are often found near coastal regions, but can be near other bodies of water. As moist air rises over a mountain range, water is dropped as rain or snow and the air loses its moisture. A desert is created on the far dry side of the range. Snowfall on the western mountain slopes California. Additionally, Nevada is nearly all located in the Great Basin area, which is fairly arid overall.
In the Turpan Depression of China, a rain shadow desert stretches for many kilometers of sand. There are a few oases and some mountain vegetation, but snow separates the Tian Shan vegetation from the rain shadow desert.
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