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Deserts take up about one third (33 percent) of the Earth's land surface.

Deserts are often composed of sand and rocky surfaces.

In hot deserts the temperature in the daytime can reach 45 °C/113 °F or higher in the summer, and dip to 0 °C/32°F or lower in the winter.

A Food Pyramid in the Hot Desert Biome      Here we see a food pyramid that shows how the Kilocalories pass up the food chain.      The first trophic level is occupied by the primary producers, which are the plants.  Plants make food through photosynthesis. The limiting factor for these plants is the shortage of water, so they produce fewer than 200 Kilocalories of food for the animals for each square meter each year.     The primary consumers, who eat the plants, occupy the second trophic level. These animals have very little to eat, and are small. Many are insects, or reptiles, who are cold blooded and who use less energy to maintain their bodies than mammals and birds do. As food for predators, they provide about 20 Kilocalories per square meter per year for predators.      The predators are the secondary consumers. They occupy the third trophic level. Again we see cold-blooded animals, such as snakes, insect-eating lizards, and tarantualas. Only about 2 Kilocalories per square meter per year are stored in their bodies. In the harsher desert environments, they are the top predators.     In areas where deserts get more rain, more plant material is produced and a few tertiary consumers may be able to survive. They form a fourth trophic level.      This diagram shows the energy available at each trophic level in the hot desert biome. These numbers tell about the numbers of Kilocalories per square meter per year.  Cold Desert Energy Pyramid  Introduction to Desert Biomes  Return to Introduction to Biomes © Elizabeth Anne Viau, 1999. This material may be used freely for instructional purposes but not sold for a price beyond the cost of reproduction. Please inform the author if you use it at eviau@earthlink.net

Mojave National PreserveWorld Deserts World Deserts North American Deserts Protecting Deserts Home Desert lands cover incredible distances. Many who have driven through deserts in the United States may think they are enormous, but they are only the fifth largest in the world covering about 500,000 square miles. By contrast the great Sahara Desert covers almost 3.5 million square miles, the Australian deserts 1.3 million square miles, the Arabian deserts 1 million square miles, while the deserts of Turkestan have 750,000 square miles. Numerous smaller deserts are also scattered across the globe. All are unique, and have adapted to their own particular environments. Global Weather PatternsDeserts tend to occur in two belts that circle the globe. Both the Northern and Southern Hemisphere have this belt located between 15 and 35 degrees latitude, roughly centered over the Tropic of Cancer and the Tropic of Capricorn. This is no accident. The sun is more directly overhead the equatorial region so it receives the most intense sunlight, and this solar energy heats the air. Hot air has two important qualities: it can hold enormous quantities of moisture, and it rises up into the atmosphere. So hot tropical air tends to be moist and rise into the atmosphere. As this air rises it cools, condensing the moisture and converting it to water where it falls as rain. This is why rain forests tend to occur near the equator. What goes up must come down, and gravity pulls this mass of rising air back to the ground. Tropical air typically falls at about 30 degrees latitude on either side of the equator and along the desert belt, but robbed of its moisture it is now hot and dry. The result are often persistent high pressure systems that tend to block incoming storms, or push them into other regions. These patterns make deserts possible, but typically other factor must also intrude to make deserts a reality.

Desert biomes can be classified according to several characteristics. There are four major types of deserts: Hot and dry Semiarid Coastal Cold

Deserts cover about one fifth of the Earth's surface and occur where rainfall is less than 50 cm/year.

The animals include small nocturnal (active at night) carnivores. The dominant animals are burrowers and kangaroo rats. There are also insects, arachnids, reptiles and birds. The animals stay inactive in protected hideaways during the hot day and come out to forage at dusk, dawn or at night, when the desert is cooler.

These ecosystems are either barren or with scanty vegetation consisting of mainly thorny bushes. Deserts are classified as warm (hot) and cold (temperate) deserts. The hot deserts are the Sahara in Northern Africa, Kalahari in Southern Africa, Thar in India, Atacama in South America, deserts of Mexico and Australia.The deserts of Iran and Turkey, Gobi desert of Mongolia, some deserts of Argentina are recognised as temperate or cold deserts. Characteristics of Desertsi) Most deserts receive some rain every year but not uniform. ii) Light green covering of annuals is seen just after rains.iii) Have scanty vegetation, clear skies, hot days and extremely cold nights. iv) Soil is rocky and encrusted with sand or salt.v) Long periods without precipitation and extreme temperature (50 - 60oC) conditions (arid lands) impose considerable restraints on the flora and fauna which inhabit there. vi) Sandy storms are very frequent.vii) Occur generally in rain shadow areas. Flora1) Includes succulents such as Cacti and Euphorbias, which can store water in their tissues. 2) Trees with long spreading roots such as Acacia, Prosopis, Phoenix (dates) are found.3) Ephemerals (short lived) such as Boerhaavia repens are seen only during rainy season. FaunaMost desert animals are nocturnal and avoid the heat of the day by burrowing into the cooler soil. Animals include ants, locusts, lizards, Gila monster, coral snake, rattle snake, burrowing owls, Gambel's quail, kangaroo rats, rabbits, camel, skunk, badger foxes, jackals and desert cats. In general, the organisms having specialised structural and physiological and behavioural adaptations to withstand the extreme temperatures only can survive in a desert.

A cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and D

A cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and D

A cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and D ry

Sahara Desert Plants The Sahara Desert is often described as a bleak and barren plain. In truth, it is very beautiful and full of different Sahara Desert plants. Sahara Desert Plants Among desert areas throughout the Earth, there are two types. The cold type of desert, which is often found in Arctic regions, is an area that gets very little precipitation. The cold desert can be covered in snow, however, and the temperatures here are chilly and unsuitable for sustaining many life forms. The other type of desert is known as the hot desert, and this is what people usually think of when they picture a desert area. This type of desert is extremely warm and dry, with temperatures reaching unbearable levels, and little to no rain to sustain those who live here. The biggest of the hot deserts is the Sahara Desert, located in Africa. Although this desert is not the most hospitable place for organisms to take up residence, the Sahara Desert plants defy the odds and thrive here.

Animals Armadillo Lizard Banded Gila Monster Bobcat Cactus Wren Coyote Desert Bighorn Sheep Desert Kangaroo Rat Desert Tortoise Javelina Cactus Ferruginoug Pygmy Owl Sonoran Desert Toad Sonoran Pronghorn Antelope Thorny Devil Climate Return to Desert

Human impact in desert areas 1700,2000 and 2050

Desert plants have developed various ways to get as much water as possible and to reduce water loss.Some plants have long roots to get water deep in the soil, or branched roots to get water over a wide area. With thick waxy layer on the stems and leaves, water can be retained and the tissues are protected from strong sunshine. Some plants have pin-like leaves to reduce water loss.        Barrel Cactus             Many desert plants are succulents and they store water in their swollen stems or leaves.  

Deserts are defined by how much rain they get. Most deserts, like the Sonoran in North America and Sahara in Africa, are hot. They receive less than 25cm of rain each year. The South and North Poles are also deserts but very cold.

The four major types of biomes are aquatic, grasslands, forests, and desert. Aquatic biomes are probably the most important of all the biomes. Their medium, water, is a major natural resource. Aquatic biomes can be subdivided into freshwater, seawater and atmospheric biomes. Grasslands can be subdivided into savanna, temperate grasslands (prairie) and tundra. This classification corresponds to decreasing average temperatures. Forests receive more precipitation than other biomes and vary from boreal, to temperate, to rainforest. This classification corresponds to increasing temperatures. Deserts have the fewest species and the most extreme climate