Dessert

A desert is a barren area of landscape where little precipitation occurs and, consequently, living
conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected
surface of the ground to the processes of denudation. About one-third of the land surface of the
world is arid or semi-arid.

 WEATHER & CLIMATE

Weather is not the same in all deserts. The seasons in hot and dry deserts are usually very
hot during the summer and warm during the rest of the year. During winter these deserts get little
rainfall. Rain is often light, or in short concentrated bursts. Most of the time evaporation rates are
faster than rainfall rates. Sometimes the rain evaporates before even hitting the ground. This is the
reason for the dry characteristic of this type of desert. Coastal deserts are in moderately cool to
warm areas. Coastal deserts usually have cool winters followed by fairly long, warm summers. The
temperature in the winters is generally 41°F (5°C) or below. In the summer the weather heats up to
between 55° and 75°F (12 and 24°C). Average rainfall is usually 3 - 5 inches (8 - 13 cm). The
Atacama is the Earth's driest desert. In the Atacama 1 millimeter or more of rain falls every 5-20
years. Cold deserts have short, moist and moderately warm summers, and long cold winters like
one could expect in Antarctica. The winter temperature ranges from -5°F to -110°F (-20.5 to -79°C),
and in the summer it can be a nice, balmy, 32°F (0°C). The coldest day recorded in Antarctica was
-113°F (-80.5°C)!

 LANDFORMS

Mountains
Mesas & Buttes
A mesa is a hill with steep sides and a flat top. A smaller mesa is sometimes called a butte.
These landforms can also be called table mountains or table hills, because the word mesa
actually means table in Spanish.
Scientists believe that mesas and buttes were formed when streams or rivers weathered
and eroded away the smaller, softer rocks, leaving only the strong rock of the mesa or butte
behind.

Bodies of Water

Rain is usually the main source of water in a desert, but it falls very rarely. Many desert
dwellers rely on groundwater, stored in aquifers below the surface. Groundwater comes
from rain or other precipitation, like snow or hail. It seeps into the ground, where it can
remain for thousands of years.

Underground water sometimes rises to the surface, forming springs or seeps. A fertile green
area called an oasis, or cienega, may exist near such a water source. About 90 major,
inhabited oases dot the Sahara. These oases are supported by some of the world’s largest
supplies of underground water. People, animals, and plants all surround these oases, which
provide stable access to water, food, and shelter.
 When groundwater doesn’t seep to the surface, people often drill into the ground to get to it.
Many desert cities, from the American Southwest to the Middle East, rely heavily on such
aquifers to fill their water needs.

Rivers sometimes provide water in a desert. The Colorado River, for instance, flows through
three deserts in the American Southwest: The Great Basin, the Sonoran, and the Mojave.
Seven states—Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona, and California—rely
on the river for some of their water supply.

People often modify rivers to help distribute and store water in a desert. The Nile River
ecosystem dominates the eastern part of the Sahara Desert, for instance. The Nile provides
the most reliable, plentiful source of freshwater in the region.

 CANYONS

Canyons & Arroyos

A canyon is a deep, narrow valley with steep sides. Canyons are usually carved out by
rivers. Over time, the rushing water weathers and erodes the land, forming a deep canyon over
thousands of years.

You have probably heard of the Grand Canyon, a 277-mile-long canyon carved out by the Colorado
River in Arizona. But did you know that the Grand Canyon is only the second-largest canyon in the
world? The longest and deepest is called the Yarlung Tsangpo Canyon, and it's in Tibet.

 ISLANDS

Animals

Fennec Foxes

Fennec foxes inhabit the Saharan desert in Africa, where temperatures average
around 104 degrees Fahrenheit. Their large ears dispel heat by filtering blood
through small capillaries in the thin ear tissue, spreading it out and cooling it before
it is circulated back into the rest of the body. Fennec foxes have thick fur on the
soles of their feet, which allows them to run over hot desert sand without pain.

Dung Beetles

There are several species of dung beetles, but most of them live in the deserts of
Australia and Africa.

Bactrian Camels
 Camels are some of the most famous desert animals. While some species have only
one hump, Bactrian camels have two. These humps serve the same function as those
of single-humped camels: They store energy-rich fat, which sustains the camels
during long treks across the desert. Many people used to believe that camel humps
contained water, which isn't true. It's easy to understand why someone might
believe this since camels can go up to seven months without drinking water.

Mexican Coyotes

Mexican coyotes are one of several coyote subspecies. As their name implies, they
live in the deserts of Mexico, as well as in California and Arizona, mostly in the
Sonoran Desert. Although coyotes are sometimes confused with wolves, these
desert canines are much smaller, usually weighing only about 30 pounds at full
adulthood.

Sidewinder Snakes

Sidewinders are one of many snake species native to deserts of the southwestern
U.S. and northwestern Mexico. These legless reptiles get their name from their
unique way of moving. Instead of slithering side to side in a straight line, as most
snakes do, sidewinders slither diagonally, whipping their bodies back and forth in
long strokes.

Thorny Devil Lizard

The thorny devil, also known as the thorny dragon, is a lizard specially equipped for
life in the deserts of Australia. They are named for the protruding, thornlike growths
that cover their skin.

Plants

Pancake Prickly Pear Cactus

Barrel Cactus
Saguaro Cactus
Brittlebush
Desert Ironwood
Desert Sage
Desert Marigold
Desert Willow Tree
Desert Lily
Turpentine Broom
Mojave-aster
Jumping Cholla
 Elephant Tree
Yellow Paloverde
Soaptree Yucca
Desert Palm

ADAPTATION NEED FOR PLANTS AND ANIMALS T SURVIVE IN THE DESERT

Plant Adaptations in the Desert Biome
In order for plants to survive in the desert, they have adaptations that allow them to collect
and store water and moisture and, prevent moisture loss. The plants in the desert biome
store water in their roots, stem, leaves, or fruit. Plants called succulents store water in their
stems or leaves. Some of the desert plants have roots that grow deep enough in the ground
that they are able to reach the water. Small, spiny leaves of the desert plants prevent evap-
oration, helping them to retain moisture. Some plants have glossy leaves that will reflect the
sun’s rays which also help them retain moisture. Some plants have a short life cycle, they
grow, flower, germinate and die within a year. Some plants will shrink in size during dry
times which allow them to use the stored moisture. The plants are often slower growing
types which require less energy (food and water).

Animal Adaptations in the Desert Biome

Animals of the desert need to adapt to intense heat and lack of water and shelters. Many of
the desert animals are only active during the evening when the temperatures are cooler.
Other animals burrow during the day to avoid the harsh conditions during the day. It is
difficult for large animals to survive the desert due to the lack of shelter to hide from prey.
Some animals don’t need to drink water as they get all the water they need from the insects,
plants and seeds that they eat. Many desert animals don’t have sweat glands which let them
retain moisture eliminating the need to drink. Birds have feathers that keep them insulated
from the strong heat of the sun. Some rodents have specialized kidneys that return their
water to the bloodstream instead of losing it through urination.

 RELATIONSHIP

Predators are animals that hunt and feed on other animals. Prey are animals
that are killed for food by a predator. A good example of the predator-prey
relationship in the Sahara Desert is the Sandy Rat, the predator and the
Kangaroo Rat, the prey. Another example is the relationship between the
Hawk, a migratory bird, eating a lizard or a chameleon.

Competitive relationship is when two or more species depend on the same

food source or any limited resource. A good example of the competitive
relationship in the Sahara Desert is when the Saharan Cheetah, Spotted
Hyena, Horned Viper, and the African Wild Dog compete with each other for
the same prey, the Addax Antelope.
 LIMITING FACTORS

Biotic and Abiotic

4 Limiting Factors:

Water is a limiting factor in the desert because due to the lack of water
plants have a hard time growing which limits the amount of plants as well as
animals in the desert. The lack of water also means that animals have adapt
in order to survive on such little amounts of water.

Climate is a limiting factor because of the extreme weather in the desert.

During the day the temperatures can reach well over 100 degrees and at
night the temperature plummets to well under freezing, making the time
animals can be out and moving around actively very little.

Food is a limiting factor because there is not enough for all the animals. Due
to the extreme condition’s animals must be able to adapt to, very few
animals live in the desert. This makes it hard for the few who do live in the
desert to find food because there aren't as many animals for them to hunt,
and plants a scarce for herbivores due to the lack of water so carnivores and
herbivores have a very hard time finding food to survive in the desert.

Competition is another limiting factor in the desert biome because for every
animal there is only so much food. An example would be with the cactus
wren bird. They rely on the cactus for food, but one cactus can only provide
so much food per cactus wren so there is fierce competition over the little
food there is. There is competition with the water as well because there is so
little water, animals really have to compete to get what trace amounts of
water there are.

ECOLOGICAL CONCERNS AND ISSUES

The climate is very hot and dry, which makes it very hard for people,
plants, and animals to live here. Because water is scarce, any form of life is
challenged, which makes these organisms have to adapt to their home. This
also applies to the small population of people living in the desert as well.
Humans have a huge effect on these biomes. Other than pollution being
spread around the world, industries are constantly digging for oil and fossil
fuels because of its high demand. Even though this may help other parts of
the world, it is destroying the deserts and disrupting the desert biomes.
 These actions can lead to extinction and it can endanger species. People who
live in deserts (specifically the Sahara) have adapted to a nomadic lifestyle,
but when they travel with their animals, they are constantly pushing the
boundaries of the desert further and further, making it larger. This can affect
the climate of the whole world, making it hotter and drier overall.

Some reasons for extinction of animals in this biome are listed below:

 Global warming is increasing the incidence of drought, which dries up water

holes.
 Higher temperatures may produce an increasing number of wildfires that
alter desert landscapes by eliminating slow-growing trees and shrubs and
replacing them with fast-growing grasses.
 Irrigation used for agriculture, may in the long term, lead to salt levels in the
soil that become too high to support plants.
 Grazing animals can destroy many desert plants and animals.
 Potassium cyanide used in gold mining may poison wildlife.
 Off-road vehicles, when used irresponsibly, can cause irreparable damage to
desert habitats.
Oil and gas production may disrupt sensitive habitat.
Nuclear waste may be dumped in deserts, which have also been used as
nuclear testing grounds.