What Are Deserts? Deserts are areas that are characterized by having little and unpredictable rainfall; less than 250 mm/year. The result is scarcity of plant and animal life. The Koppen  system of climate classification relates the definition of a desert to plant and animals by characterizing a desert as a place where more water would be lost through evaporation than gained from precipitation. Deserts are not static; they are constantly expanding and contracting with changes in the climate and landscape.
They are one of the most extensive environments on the planet, comprising up to 0% of the terrestrial surface . Deserts are also natural laboratories in which to study the interactions of wind and sometimes water on the arid surfaces of planets. They contain valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Because deserts are dry, they are ideal places for human artifacts and fossils to be preserved. Deserts are also fragile environments. The misuse of these lands is a serious and growing problem in parts of our world.
Approximately one-third of the Earth’s land surface is desert, arid land with meager ainfall that supports only sparse vegetation and a limited population of people and animals. Deserts have also been portrayed as fascinating environments of adventure and exploration from narratives such as that of Lawrence of Arabia to movies such as “Dune. ” These arid regions are called deserts because they are dry. They may be hot, they may be cold. They may be regions of sand or vast areas of rocks and gravel peppered with occasional plants. But deserts are always dry.  Features of Deserts Lack of water is the fundamental factor in defining a desert.
Perveril Meigs for UNESCO set up a system balancing rainfall with water lost via evaporation and transpiration. He described three zones: arid, semi-arid, and hyper-arid. Arid zones receive less than 200 mm/year while semi-arid zones receive less than 600 mm/year. Hyper-arid zones are by far the driest areas, receiving less than 25 mm/year . High temperatures are often correlated with deserts. These temperatures often experience fluctuations up to 20 C each day . These extreme temperature fluctuations along with unpredictable rainfall patterns (some areas, such as Death Valley in Calitornia, do not receive rain tor up to 3 years! lants and animals to survive . Why are there deserts? make i t very difficult tor As stated above, low rainfall and high relative degree of water loss characterize deserts. These areas may be the result of various factors such as high pressure zones, continentally, cold ocean currents, and/or rain shadows. High pressure zones in the subtropical regions are where many deserts are located, around 30 degrees north and 30 degrees south latitudes. These zones are created by Hadley Cells, a convection pattern resulting from solar energy. The process is such that:
1 . Air is heated in greater amounts at the equator because the angle of light hitting the Earth is closer to perpendicular. That is there is less surface area exposed to higher amounts of radiation, and increased warming results.
2. This warm air expands and rises at the equator, creating low pressure zones.
3. These low pressure zones suck in moisture-bearing masses, or rain-clouds, while the equatorial air masses travel towards the poles. Also, these rising masses cannot retain as much water as they continue to rise because they are cooling, which results in high rainfall at the equator, i. e. equatorial rainforests. As these equatorial air masses travel away from the equator, they cool in temperature, and descend closer to the surface of the globe.
5. High air pressure and increased dryness results as the air masses near the surface.
6. Moisture is sucked from the surface at 30 degrees north and 30 degrees south because the air masses are increasing in temperature and are able to hold more water . Rain shadows are also often involved in desert formation. Mountain ranges cause air to rise and cool, leading to precipitation. As a result, this cooled air drops and sucks up moisture from the area preceding the mountain range.
Rain shadows have been one of the main factors in the formation of deserts in North America, especially the Rocky Mountains in the western United States. As an area of land is located more toward the interior of a continent, less water from the ocean, via winds, tends to reach the area. This phenomenon is known as continentally and is thought to be one of the main factors in the formation of deserts in central Asia. Cold ocean currents seem to play an important role as well. Currents coming from the poles to the tropics consisting of cold water create cold air masses which cannot hold uch moisture .
Because most of the moisture is dumped before the air mass reaches the land, this dry air sucks up moisture from the land, resulting in coastal deserts . Deserts, as biomes The dry desert is in Kppen’s  BWh (German letters for following English translations. B) climate category. It is a Low Latitude climate. The B stands for Dry Desert climates. All months have average temperatures over 640 F (180 C). The W stands for desert climate. Finally, the H stands for dry and hot, with average annual temperatures over 64 C) The description ot this marvelous biome climate is uite odd, but also as it is odd, it is also very interesting.
Dry Desert climates are formed by high-pressure zones in which cold air descends. Then the descending air becomes warm but, instead of releasing rain, the heat from the ground evaporates the water before it can come down as rain. The ground is extremely hot because the sun’s rays beat down on it directly overhead. Not a lot of atmosphere to protect it from radiant energy. As stated above, approximately 1 in. (. 25 cm) of rain falls in dry deserts per year. The average annual temperature of these miles of hot sand is 640 F 180 C). The latitude range is 15-280 north and south of the equator.
Their global range covers about 1/5 of the earth, including the world’s great deserts: Sahara, Sonora, Thar, Kalahari and the Great Australian Desert. Plants of the Dry Desert have adapted to the lack of water by using dew for moisture and taking in water through their leaves and stems. [1 1] Desert’s Vegetation: Plants of the Desert habitat area have adapted to its dry, hot extremes by using both physical and behavioral mechanisms. Plants that have adapted by altering their physical structure are called xerophytes. Xerophytes, such as cacti, usually have special ways of storing and conserving water.
They often have few or no leaves, which reduce water loss. Phraetophytes are plants that have adapted to living in the desert by growing very long roots, allowing them to get their moisture deep within the earth, at or near the water table. Perennials (plants which live for years) and annuals (plants which live one season) also have behavioral adaptations. The perennials survive by remaining dormant during the dry periods and come to life when water is available. Annuals germinate after heavy rain and omplete their reproductive cycle quickly. They bloom for a few weeks in spring.
Their seeds remain dormant in the soil until the next year’s rain. Below are a few of the plants you will see in the desert. Interesting facts are also given for each plant.  Plants in Deserts First idea that comes while thinking of deserts maybe its sand, heat, or Gila monsters, but most likely its cactus. Cacti are probably the most memorable characteristic of the desert. In all of the Speedy Gonzales cartoons, Speedy is an obvious example of the back ground people have of deserts, having cacti as a harmful tangible plant. Barrel Cactus is one of the most famous plants in American deserts.
The Barrel cactus can be easily distinguished from other cacti. because of it cylinder-shaped body. The cactus usually reaches from around five to eleven feet tall, and at that height it is one of the largest cacti in the North American deserts. Cactus is really a man-sized (or bigger) cylinder with numerous parallel ridges that run down the sides. These ridges are topped with dangerously sharp 3-4 inch spines. The barrel cactus is also a flowering plant. It has rings of yellow-green or red blossoms at its top. Like many plants ot the world, this cactus nas numerous uses.
Native Americans who lived in the desert found the barrel cactus very useful. The Native Americans had to look hard to find food. The barrel cactus provided some very important provisions for them. They stewed the Barrel Cactus to make a cabbage-like food. They got water to drink from the pulp and they made fish hooks from the spines, which are pointed at the end. The pulp is also made into “cactus candy”. The Barrel cactus is found in the Mojave, Sonora, and the Chihuahua deserts. These deserts are found in the land of Speedy and the Roadrunner: Baja, Arizona, California, Texas, and Central Mexico.
The barrel cactus grows in the desert washes and slopes, but can also be spotted growing along canyon walls.  Brittlebushes The brittlebushes are common plants of the Mojave and Sonoran deserts. They are a small deciduous shrub which grows as a low, roundish mound 2 to 5 feet high. Brittle branches sprout from a woody trunk. The leaves have serrated edges, and are broader at the base than at the tip. They are about 1 to 4 inches long. The leaves are covered with a thick mat of short hairs giving a gray-green appearance. Many desert plants have this kind of hairy leaf.
The hairs form a blanket over the leaves and act an insulating layer against the heat and cold. They also trap any moisture that is in the air, and reduce the amount of water lost to dry air. The brittlebush flowers from March to June, turning the desert from sand orange to bright yellow. It’s a member of the sunflower family and its flowers resemble the sunflower, only in miniature form. The flower is disk shaped, on long bare stems, rising several inches above the mound of white leaves, giving an impression of a layer of color over the plant.
It has a solitary head with a dark yellow-orange to purplish mound of disk-corollas from which radiate 1 inch yellow rays with a lobed, squared off tip. Brittlebush can be found growing in the coastal chaparral and interior valleys of southern California, east to the creosote bush scrub, Death Valley through the Mojave Desert and the Colorado Desert, and south to Baja California. It likes to grow in dry slopes and washes. In most of these areas, the brittlebush and creosote bush dominate the vegetation. Brittlebush has had many uses in the past. The stems of the brittlebush secrete a clear resin which was used by Native
Americans from the Southwest as glue and also as a gum. Ground up it was used by the Seri Indians of Mexico as toothpaste. They also would sprinkle the paste on sores or heat it and spread it on their bodies to relieve pain. The early Spanish missionaries burned it as incense. Mule deer and dese rt bighorn sheep browse on it, and kangaroo rats will eat its seeds, but arent all that fond of it. Other than that, it isn’t used for domestic livestock. Brittlebush is most useful for rehabilitating landscapes, and stabilizing disturbed areas. It is used in Arizona to minimize erosion near highways.
It can be easily transplanted and grows well from seeds. The brittlebush is very abundant and is not on the endangered species list.  Chain Fruit Cholla Another important plant is the chain fruit cholla that looks as much like a tree in the desert as a cactus possibly can. It has a central trunk from which sprout many spiny “branches”. It is commonly found in dry, sandy soils of BaJadas, valleys floors, and plains of the Sonoran and Chihuahua Desert, south Arizona and northwest Mexico. It is found at elevations up to 4,000 feet above sea level. The chain fruit cholla is a shrubby cactus.
It has many segmented, irregular, drooping branches. These are covered with a dense layer of sharp spines. These spines have a straw-colored sheath when young which turns a dark gray as they mature. The sheath acts to reflect sunlight and prevent overheating. As the cholla gets older the spines fall off and leave a rough and scaly bark on the trunk and old branches. It is the largest of the cholla, and can grow to a height of 15 feet, and be 6 feet across. They attach themselves to desert animals and are dispersed for short distances. The ground around a cholla is usually covered with segments that have fallen off the parent.
The fruit is not always fertile and the cholla relies mainly on fallen stem Joints and fruit to take root and grow new plants. During droughts animals like the Bighorn Sheep rely on the Juicy fruit for food and water. Large forests of chain fruit cholla grow in Arizona. The cactus is not considered to be vulnerable or endangered, mostly because they grow in inaccessible and hostile places of the desert.  Other plants in desert include [1 5] Creosote Bush Crimson Hedgehog Cactus Desert Ironwood Joshua Tree Jumping HYPERLINK “http://www. blueplanetbiomes. org/]umping_cholla. htm”cholla Mojave Aster
Ocotillo Palo Verde Pancake Prickly Pear Cactus Animals in Deserts Armadillo Lizard First and most desert populating animal is the Armadillo Lizard. The nostrils of the Armadillo Lizard are formed into little tubes. The tubes help the Armadillo Lizards smell tor t or predators. A ground dwelling lizard, it is active in the daytime and feeds on a wide variety of insects, as well as on spiders and other invertebrates. The head of the Armadillo Lizard is narrow in shape. It is fairly slow moving animal, but when the Armadillo Lizard thinks or knows it’s in danger, it runs as fast as it can go for cover.
The body length is 15-17 inches, the tail is 14-16 inches long, and it weighs 8-17 lbs. Its back legs are a little shorter than the front. The head, body, and club-like tail are all flattened, enabling it to wriggle easily into rock crevices for shelter. It may also adopt a curious defensive posture when threatened by rolling itself up like an Armadillo, with its tail tightly held in its Jaws, presenting a spiny ring to the predator and protecting the softer, vulnerable belly area. That’s why it’s called the Armadillo Lizard. The armored Armadillo Lizard has protection all around its body so that redators can’t harm any of it’s under parts.
Also squeeze into small places for escape. Another protection is their spiny scales that go all the way around its body. Their tails and spines also can be used to defend themselves as well. The Armadillo Lizard can be found in the deserts of the southern tip of Africa. The Armadillo Lizard has its babies in the late summer. Only 1 or 2 babies are born during that time. The Armadillo Lizards stay in family groups, and they will all live in the same rock crevice. When the lizards give birth, the babies are live-born, but do have a thin embranous shell that they need to break through.
The Armadillo Lizard is a prey animal. It is preyed upon by bigger and stronger predators, such as humans, etc. The Armadillo Lizard’s armor is most useful against many birds, mammals, and other reptiles. The Armadillo Lizard is not an endangered species although it does have a lot of enemies to protect itself from. The Cape Provincial Ordinance helps the Armadillo Lizards when their injured or sick. That way the Armadillo lizards can be less endangered.  Bobcat Bobcats are also widely known animals around the globe; however not much now about its desert presence.
The average bobcat weighs 15 to 20 pounds, and is 2 feet tall and 3 to 4 feet long. The bobcat looks pretty much like a regular cat except bigger. The desert bobcat’s color is a mixture of white, black, brown, and orange. The bobcat often gets confused with the mountain lion because of its fearsome growl. Bobcats can be found almost anywhere, but one of the most common places is the southwest desert. They like it there the most because of the bushy and rocky terrain. The bushes give shade if it’s hot, and the rocks are a perfect hiding spot if they’re hunting prey.
The bobcat’s diet consists of rabbits, squirrels, mice, gophers, rats, and fish. They’re good at catching all their prey because of their hunting ability. A bobcat’s mating is a lot like a regular house cats mating. That’s one similarity that they have. Bobcats will have one litter of kittens a year. A litter of bobcats consists of 2 to 3 kittens. When food is scarce, a bobcat will not have a litter at all. When a female has kittens, she will only hunt right around her den and not use all of her hunting territory. She will wean the kittens by three months and then bring back killed animals.
Once they get used to eating meat, she brings them back live prey so they can practice hunting and killing. They will stay with the mother for almost one year, leaving in the spring. Despite the bobcat’s cute appearance it is actually very fierce and can kill animals as large as deer. A good thing about the bobcat is it wont kill any healthy large prey unless it’s desperate. The bobcat always goes for the sick or wounded first. This is good because the sick wont spread disease to others. Bobcats are loners. Each bobcat has its own territory which it will not share with other bobcats, except for females.
The bobcat’s status in the wild used to be very plentiful, but too many people took advantage of that and almost killed them off. A good thing now is that the big game people are protecting them.  Coyotes The Coyote has a tan coat mixed with hairs of rusty brown and gray, and the ends of the hair may be black. The different colors help to hide the coyote in the underbrush, rocks, and grasses. The coyote has large, pointed ears and a bushy tail. Coyotes are known for their sharp eyesight, keen hearing and a keen sense of smell. Adult coyotes can grow to be 4 feet long (including the tail which can be 11 – 16 inches ong).
They can be 2 feet tall and weigh up to 30 pounds. Coyotes once only lived in Western America, but people have forced them to find other habitats. Coyotes can be found in the United States, Canada, and Mexico. They live in all kinds of habitats including deserts, prairies and mountains. Coyotes have even been found on Cape Cod. Coyotes eat mostly rabbits and rodents. They also hunt antelope, goats, sheep, and other animals. They will eat insects and reptiles. Dead elk and deer, as well as cattle will become the main food in the northern wintertime. Coyotes will also eat fruits and nuts.
As coyotes are forced to move closer to people, they will also eat garbage. Most coyotes live alone or in pairs. They might live together in larger groups. Coyote families guard and mark their own areas. Pups are born in the spring. A female can have from 3 – 12 pups. Both parents care for and feed the pups. Coyote’s coloring helps it to hide in the desert and hunt for its prey. Coyotes will eat almost anything available to them where ever they are; fruits, rodents, small animals, and garbage. Coyotes are clever animals and adjust to their environment. Coyotes are not endangered.
Their natural enemies include ountain lions and more recently man.  The Desert Tortoise The Desert Tortoise can be tound in the Mojave and Sonoran Deserts ot southern California, two of North America’s four deserts. They inhabit semi-arid grasslands, gravelly desert washes and sandy canyon bottoms below 3,500 ft. The Desert Tortoises is a land dwelling turtle belonging to the Testudinidae family. The Desert Tortoise is also known as a gopher tortoise because it belongs to one of 4 species of the Gophers genus. Its front legs are muscular and flattened with long claws, and are very well adapted for digging deep burrows.
Desert Tortoises can make hissing, popping, and poinking sounds, usually out of fear or distress. Its domed, brown shell (carapace) can grow to be 9-15 inches in length, 4-6 inches high, and the tortoise can weigh from 8 to 15 lbs. They usually live to be about 80 years, but some have been known to be a 100 years old. Both sexes have an extension on the front of their lower shell called a gular horn. The horn is longer on the males and they will use them to upturn rival males. Males will fght each other whenever they meet. These fghts usually end with the defeated male scurrying away.
Males and females will share crevices and burrows to get out of the extreme heat of the day, but when they emerge, the males will again try to upturn each other. To escape the heat of the summer and the cold of winter the desert tortoises live in burrows which they dig. Some of them can be three to six feet deep. They will spend November through February in a torpid state in their underground burrows. Some burrows have been used for over a hundred years. 95% of a tortoise’s life is spent underground. Their most active time is in the spring when they will forage for herbs, grasses, new growth of cactus and annual flowers.
Desert Tortoises will develop a preference for certain plants, to which their digestive systems become accustomed. When forced to eat unfamiliar plants, their digestive tract need several months to become accustomed to them and be able to extract all available nutrients and water from them. Because they only have a few months in the spring to take in enough water to last them all year, destruction of their habitats and the plants in it can be fatal to the desert tortoise in the long run. The Desert Tortoise will dig catch basins in the soil to catch the infrequent rain that falls.
They remember where the asins are and return to them when it rains. Most of their water intake comes from moisture found in the grasses and wildflowers they eat in the spring. The tortoise has the ability to store about a quart of water in its bladder to be used when necessary. Adult Desert Tortoises can go for years without water. The Desert Tortoise will mate anytime it is above the ground. The females can store sperm and will lay a clutch of 4-8 hard-shelled eggs in a nest dug near the burrow opening in May, June, and July. She can lay 2 to 3 clutches a year. The female will leave the nest and the eggs are then incubated by the warm soil.
After 90 to 120 days the young tortoises hatch. Only a few out of every hundreds of the 2-3 inch hatchlings will make it to adulthood. Their shells stay soft for the first 5 years and they are preyed upon by coyotes, roadrunners, Gila monsters, and ravens (Corvus corax). In some parts of the Mojave Desert ravens are responsible for the death of about 50% of the Juvenile Desert Tortoises. Another reason the Desert Tortoise population grows slowly is because they don’t reproduce very fast. Females dont breed until they are 1 5 to 20 years old and then may only lay eggs if there is enough food available.
Their birth intervals are 3 years. It is unlawtul to touch, harm, harass or collect a wild Desert Tortoise. W frightened they will empty their bladder as a defense mechanism, and the loss of water can be fatal to the tortoise. The Desert Tortoise is considered a “threatened” species under the California state Endangered Species Act in 1989 and the federal Endangered Species Act in 1990. Illegal collection for the pet trade, destruction of their habitats by urban area expansion and by off-road vehicles, and increased predation by ravens are some of the factors contributing to the Desert Tortoise’s decline.
Several military bases there use the desert as a practice range, and people race off-road vehicles through it, destroying the forage plants and crushing vulnerable Juvenile Desert Tortoises. The population of the Desert Tortoise in the Mojave Desert has gone down 90% since 1980. Even though a desert looks empty and lifeless, it is filled with many species of animals, like the Desert Tortoise, who need our special consideration.  List of Notable Deserts around the World Asian Deserts Several significant deserts stretch across Asia and the Middle East.
These include the Karakum, Kyzylkum and Rub’ al Khali. 20] Rub’ al Khali: or Empty Quarter is the largest sand desert in the world, encompassing most of the southern third of the Arabian Peninsula, including Saudi Arabia and areas of Oman, the United Arab Emirates, and Yemen. The desert covers some 650,000 square kilometers (250,000 sq. m’) Karakum Desert: is a desert in Central Asia. Its name means Black Sand in Turkic languages. It occupies about 70 percent, or 350,000 km2, of the area of Turkmenistan . Kyzylkum Kum: is the 16th largest desert in the world. Its name means Red Sand in Turkic languages.
It is located in Central Asia in he doab between the rivers Amu Darya and Syr Darya, and is divided between Kazakhstan, Uzbekistan and (partly) Turkmenistan. It covers about 298,000 km2 . European Deserts Europe has a lot of deserts, however most of its deserts do not include the actual sand deserts like the rest of the world, rather gravel or green semi-covered desert over small areas called deserts. Therefore there are only a few deserts of which include. Accona Desert: is a semi-arid area in Tuscany, Italy, in the center of the so- called Crete senesi, in the west and the south of the commune of Asciano. 
Causse du Larzac: is a limestone karst plateau in the south of the Massif Central, France, situated between Millau (Aveyron) and Lod?©ve(H?©rault). It is an agricultural area, where sheep are bred to produce milk for Roquefort cheese.  Atrican Deserts Deserts in Africa make up around 25% of the geographical area of the continent. Thus, containing some notable deserts.  The Great Sahara: is the world’s hottest desert, and the third largest desert after Antarctica and the Arctic. At over 9,400,000 square kilometers (3,600,000 sq m’), it covers most of North Africa, making it almost as large as China or the United States. 6] The Kalahari Desert: is a large semi-arid sandy savannah in southern Africa extending 900,000 square kilometres (350,000 sq mi), covering much of Botswana and parts of Namibia and South Africa.  The Libyan Desert: covers an area of approximately 1 , 100,000 km2, it extends approximately 1100 km from east to west, and 1,000 km from north to south, in about the shape of a rectangle.  North American Deserts North America has four major deserts: Great Basin, Mohave, Chihuahua and Sonoran. These are the vastest in the continent, including the American wild life animals and plants. 9] Chihuahua Desert: is a desert, and an Eco region designation, that straddles the U. S. -Mexico border in the central and northern portions of the Mexican Plateau.  Great Basin: is the largest US desert and covers 190,000 square miles. It is bordered by the Sierra Nevada Range on the west and the Rocky Mountains on the east, the Columbia Plateau to the north and the Mojave and Sonoran deserts to the south.  Mohave Desert: is a desert which occupies a significant portion of southeastern California and smaller parts of central; southern Nevada, southwestern Utah and northwestern Arizona in the United States. 2] Sonoran Desert: is a North American desert which covers large parts of the Southwestern United States in Arizona, California, Northwest Mexico in Sonora, Baja California, and Baja California Sur. It is one of the largest and hottest deserts in North America, with an area of 311,000 square kilometers (120,000 sq mi).  South American Deserts South America is nonetheless one of the most mixed lands of forests, tundra’s and mountains. However, South America is home to different deserts of which are tourists’ choices due to important factors of beauty.
The Atacama Desert: Spanish: Desierto de Atacama) is a plateau in South America, covering a 1,000- kilometre (600 m’) strip of land on the Pacific coast, west of the Andes mountains. It is the driest hot desert in the world. The Atacama occupies 105,000 square kilometers (41,000 sq mi) composed mostly of salt lakes (salares), sand, and felsic lava flows towards the Andes.  Patagonian Desert: also known as the Patagonia Desert or the Patagonian Steppe is the largest desert in Argentina and is the 7th largest desert in the world by area, occupying 673,000 square kilometers (260,000 mi2).