Thursday, January 13, 2011


What is a Desert Like?
The hot desert is a land of extremes: extreme heat and extreme dryness; sudden flash floods and cold nights. Because deserts are such a harsh environment, deserts often have names likes "Death Valley," "the empty quarter," and "the place from where there is no return."
Graph of Biome PrecipitationDeserts are usually very, very dry. Even the wettest deserts get less than ten inches of precipitation a year.
In most places, rain falls steadily throughout the year. But in the desert, there may be only a few periods of rains per year with a lot of time between rains. When it does rain, there may be quite a downpour! After the rain, desert flowers bloom.
Hot During the Day, Cool at Night
Everyone knows that during the day many deserts are hot, very hot. Temperatures in excess of 100 degrees fahrenheit are not uncommon. Yet at night, the same deserts can have temperatures fall into the 40s or 50s? Why?
Other biomes are insulated by their humidity (water vapor in the air). Temperate deciduous forests, for example, may have 80 percent humidity or more during the day. This water reflects and absorbs sunlight and the energy it brings. At night the water acts like a blanket, trapping heat inside the forest. 
Since deserts usually have only between 10 and 20 percent humidity to trap temperatures and have so few trees and other vegetation to retain heat, they cool down rapidly when the sun sets, and heat up quickly after the sun rises.

Types of Deserts Believe it or not, deserts come in several varieties. The two major classifications are hot and cold. Most of the information in this web site pertains to hot deserts.

Hot Deserts of the World
The main form of precipitation in a hot desert is rain. But that's only ten inches or less of rain per year.
Hot Deserts of the World
Size Physical 
Some Plants & Animals Special Facts
Arabian Peninsula
900,000 mi2
2,300,000 km2
Covered almost entirely by sand; has some of the most extensive stretches of sand dunes in the world. acacia, oleander, saltbush  desert locust, dromedary camel, gazelle, lizard, jackal, oryx  Nomadic Bedouin tribes have travelled through the Arabian Desert for thousands of years.
Australian (Great Sandy, Victoria, Simpson, Gibson, and Sturt)
890,00 mi2
2,300,000 km2
(1/3 of Australia) 
Great Sandy, Victoria, and Simpson are sandy; Gibson and Sturt are stony. acacia, casuarina tree, eucalyptus, saltbush, spinifex grass blue-tongued lizard, dingo, fat-tailed mouse, kangaroo, marsupial mole, rabbit-eared bandicoot, sand goanna, spinifex hopping mouse, throny devil  Aborigines have lived in the Australian deserts for over 30,000 years.
North Central Mexico and Southwestern United States (Arizona, New Mexico, Texas)
175,000 mi2
455,000 km2
High plateau covered by stony areas and sandy soil. Many mountains and mesas. cacti, chihuahuan flax, creosote bush, lechuguilla, mesquite, mexican gold poppy  coyote, diamondback rattlesnake, javelina, kangaroo rat, roadrunner Largest North American desert. Big Bend National Park located here; more species of birds seen in Big Bend than in any other National Park in the U.S.
Southwestern Africa
200,000 mi2
520,000 km2
Covered by sand dunes and gravel plains. acacia, aloe  gazelle, gerbil, ground squirrel, hyena, jackel, sandgrouse, springbok Bushman have lived in the Kalahari for 20,000 years.
Southwestern United States (Arizona, California, Nevada)
25,000 mi2
65,000 km2
Covered by sandy soil, gravelly pavement, and salt flats. creosote bush, desert sand verbena, joshua tree, mesquite  bighorn sheep, chuckwalla, coyote, jackrabbit, sidewinder, zebra-tailed lizard  Death Valley located in this desert.
125,000 mi2
325,000 km2
Covered by sand and soil cardon cactus, creosote bush, paloverde  armadillo, cavy, jaguarundi, puma, tinamou, tuco-tuco Very similar to the Sonoran Desert
Northern Africa
3,500,000 mi2
9,100,000 km2
Covered by mountains, rocky areas, gravel plains, salt flats, huge areas of dunes. Areas in the central sometimes get no rain for years at a time. acacia, grasses, tamarisks  addax antelope, dorcas gazelle, fennec fox, horned viper, jackal, jerboa, sandgrouse, spiny-yailed lizard  Largest desert in the world. Fewer than 2 million inhabitants (mostly nomads such as the Tuareg). Crossed by Arab caravans since the 10th century. 
Southwestern United States (Arizona, California) and parts of Mexico (Baja Peninsula, Sonora)
120,000 mi2
312,000 km2
Covered by sand, soil, and gravelly pavement. Gets more rain than any other North American desert. agave, coulter's globemallow, creosote bush, desert mariposa lily, mesquite, ocotillo, paloverde, saguaro  coati, elf owl, gila monster, kangaroo rat, pack rat, roadrunner, sidewinder, tarantula  Most complex animal-plant community of any desert.  One of the most beautiful deserts in the world.
India and Pakistan
77,000 mi2
200,000 km2
Majority of desert covered by sand dunes; rest covered by gravel plains acacia, euphorbias, grasses, shrubs  black buck, dromedary camel, great Indian bustard, Indian spiny-tailed lizard, jackel, sandgrouse 

Cold Deserts of the World
The main form of precipitation in a cold desert is snow or fog.
Cold Deserts of the World
Size Physical 
Some Plants & Animals Special Facts
Coasts of Peru and Chile
54,000 mi2
140,000 km2
Covered by sand dunes and pebbles. One of the driest areas on earth. bunchgrass, cardon cactus, tamaruga trees lizards, llama, Peruvian fox, nesting area for many seabirds Only a few thousand people (mostly farmers) live in the inland desert areas. Large deposits of sodium nitrate are found in the desert. Sodium nitrate is used to make gunpowder.
Northern China and Southern Mongolia
450,000 mi2
1,200,000 km2
Covered by sandy soil and areas of small stones called "gobi." camel's thorn, grasses bactrian bamel, gazelle, gerbil, jerboa, lizards, onager, wolf Crossed by Genghis Khan in the early 13th century. Many nomads now settling on government-run farms.
Great Basin
Western United States (Idaho, Nevada, Oregon, and Utah)
158,000 mi2
411,000 km2
Covered by sand, gravel, and clay. Many moutains ranges, basins, and large expanses of salt flats. greasewood, sagebrush, shadscale bighorn sheep, jackrabbit, pocket mouse, poor-will, pronghorn antelope, sage thrasher, side-blotched lizard Great Salt Lake located here.
Iran, Afghanistan, and Pakistan
150,000 mi2
390,000 km2
Covered by coarse gray soil, stony pavement, and salt flats. grasses, pistachio trees, shrubs monitor lizard, onager, oryx, scorpion World's largest salt flat located here.
Coasts of Southwestern Africa
52,000 mi2
135,000 km2
Covered by sand dunes along the coast and gravel farther inland. aloe, bunchgrass, lichens, welwitschia darkling beetle, fringe-toed lizard, golden mole, jackal, sidewinder, viper, web-footed gecko Coast of the Namib Desert is world's greatest source of gemstones.
Takla Makan
Western China
600,000 mi2
Covered by sand dunes and rocky soil. grasses, shrubs bactrian camel, jerboa, long-eared hedgehog, gazelle The word "Takla Makan" means "place from which there is no return." Crossed by Marco Polo in the 13th Century.
Parts of the Middle East and Southwestern Russia
215,000 mi2
559,000 km2
Covered mostly by extensive stretches of sand dunes. alhagi shrub, saxaul tree, sedges, thick ground cover desert tortoise, gazelle, gerbil, saiga antelope Crossed by caravans following silk route from China in Europe in ancient times. The great city of Samarkand, once a cultural and religious center of central Asia, was located here.

Where Are Deserts Located?
Biome Map
Many deserts are found in bands along 30 degrees latitude north and 30 degrees latitude south (between the red lines on the map).
Some deserts located by mountains and are caused by the "rainshadow" effect. As air moves up over a mountain range, it gets cold and loses the ability to hold moisture -- so it rains or snows. When the air moves down the other side of the mountain, it gets warmer. Warm air can hold lots of moisture, so it doesn't rain as much, and a desert is formed.

Desert Plants
Roderick and Friends with Cacti in GreenhouseDeserts are the home to many living things. In fact, deserts are second only to tropical rainforests in the variety of plant and animal species that live there. How do you think plants grow in a place that is very, very dry? 
Many of the fascinating features of desert plants are adaptations -- traits that help the plant survive in its harsh environment. Desert plants have two main adaptations: 
    Ability to collect and store water  Features that reduce water loss 
Desert plants often look different than plants in any other biome. Click on the questions to your left to learn more about desert plants and see their pictures. 

SaguaroThe stem of the Saguaro Cactus stores all of its water. The stem is green. Photosynthesis occurs in the top layer of the stem instead of in leaves. This plant has another adaptation that is hidden from us. This is its large net of roots -- that extend far away from its trunk. How would these roots help a desert plant? The roots collect water after rain. Stored in the pleated expandable stem, the water keeps the saguaro alive until the next rain. Saguaro fruit is used in jam and woody skeletons are used in building materials. The Saguaro only grows in the Sonoran Desert.

Barrel Cactus
Barrel CactusThe pleated shape of the Barrel Cactus allows it to expand when it rains and store water in its spongy tissue. It shrinks in size during dry times as it uses the stored water. 

Old Man Cactus
Old Man CactusThe white hairy surface of the Old Man Cactus helps the plant reflect the hot desert sun.

Prickly Pear Cactus
Since many desert plants store water in their spongy tissue, animals will eat them for the moisture. The thorns keep them safe from many animal predators. You can find lots of Prickly Pear Cactus in the Chihuahuan desert.

Desert Animals
Animals in the desert must survive in a hostile environment. Intense heat, searing sun, and lack of water are just a few of the challenges facing desert animals.  Animals that live in the hot desert have many adaptations. Some animals never drink, but get their water from seeds (some can contain up to 50% water) and plants. Many animals are nocturnal, sleeping during the hot day and only coming out at night to eat and hunt. Some animals rarely spend any time above ground. Spadefoot toads spend nine months of every year underground! 

Class: Mammalia: Mammals Diet: Plants
Order: Artiodactyla: Even-toed Ungulates 
Size: body:1.3 m (4 1/4 ft), tail: 25 - 35 cm (9 3/4 - 13 3/4 in)
Family: Bovidae: Bovids Conservation Status: Critically endangered
Scientific Name: Addax nasomaculatus Habitat: sandy and stony desert
Range: Africa: E. Mauritania, W. Mali; patchy distribution in Algeria, Chad, Niger and Sudan 
Cactus Wren
Cactus Wren
Class: Aves: Birds Diet: Insects
Order: Passeriformes: Perching birds 
Size: body:18 - 22 cm (7 - 8 1/2 in)
Family: Troglodytidae: Wrens Conservation Status: Non-threatened
Scientific Name: Campylorhynchus brunneicapillus Habitat: desert, arid scrubland
Range: Southwestern U.S.A. to central Mexico

Desert Lark
Desert Lark
Class: Aves: Birds Diet: Seeds
Order: Passeriformes: Perching birds 
Size: body:15 cm (6 in)
Family: Alaudidae: Larks Conservation Status: Non-threatened
Scientific Name: Ammomanes deserti Habitat: stony, hilly desert, dry wooded slopes
Range: Africa: Sahara; Middle East, through Iran to Afghanistan

Class: Mammalia: Mammals Diet: Large mammals
Order: Carnivora: Carnivores 
Size: body:about 1.5 m (5 ft), tail: about 35 cm (13 3/4 in)
Family: Canidae: Dogs, Foxes Conservation Status: Non-threatened
Scientific Name: Canis dingo Habitat: sandy desert to wet and dry sclerophyll forest
Range: Australia

Fat Sand Rat
Fat Sand Rat
Class: Mammalia: Mammals Diet: Seeds, vegetation
Order: Rodentia: Rodents 
Size: body:14 - 18.5 cm (5 1/2 - 7 1/4 in), tail: 12 - 15 cm (4 3/4 - 6 in)
Family: Gerbillinae: Gerbils Conservation Status: Non-threatened
Scientific Name: Psammomys obesus Habitat: sandy desert
Range: Algeria, east to Saudi Arabia

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