2. DESERT
250 millimetres (10 in) of average annual precipitation, and
semideserts or steppes, which receive between 250 millimetres
(10 in) and 400 to 500 millimetres (16 to 20 in). Deserts can
also be described as areas where more water is lost
by evapotranspirationthan falls as precipitation. In the Köppen
climate classification system, deserts are classed as (hot
desert) or (temperate desert). In the Thornthwaite climate
classification system, deserts would be classified as
arid megathA desert is a landscape or region that receives an
extremely low amount of precipitation, less than enough to
support growth of most plants. Most deserts have an average
annual precipitation of less than 400 millimetres (16 in). A
common definition distinguishes between true deserts, which
receive less than ermal climates.
3.
4. Deserts are part of a wide classification of regions that,
on an average annual basis, have a moisture deficit (i.e.
they can potentially lose more than is received). Deserts
are located where vegetation cover is sparse to almost
nonexistent.take up about one fifth (20%) of the Earth's
land surface. Hot deserts usually have a
large diurnal and seasonal temperature range, with high
daytime temperatures, and low nighttime temperatures
(due to extremely low humidity). 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 at
nighttime in the winter. Water vapor in the atmosphere
acts to trap long wave infrared radiation from the ground,
and dry desert air is incapable of blockingsunlight during
the day (due to absence of clouds) or trapping
heat during the night.
5.
6. TEMPERATURE OF DESERT
Thus, during daylight most of the sun's heat reaches the
ground, and as soon as the sun sets the desert cools quickly by
radiating its heat into space. Urban areas in deserts lack large
(more than 14 °C/25 °F) daily temperature variations, partially
due to the urban heat island effect.
Many deserts are formed by rain shadows; mountains blocking
the path of precipitation to the desert (on the lee side of the
mountain). Deserts are often composed
of sand and rocky surfaces. Sand dunes called ergs and stony
surfaces called Hamada surfaces compose a minority of desert
surfaces. Exposures of rocky terrain are typical, and reflect
minimal soil development and sparseness of vegetation. The
soil is rocky because of the low chemical weathering, and
relative absence of a humus fraction.
7.
8. DEFINITION
Measurement of rainfall alone cannot provide an accurate
definition of what a desert is because being arid also
depends on evaporation, which depends in part
on temperature. For example, Phoenix, Arizona receives
less than 250 millimeters (10 in) of precipitation per year,
and is immediately recognized as being located in a
desert due to its arid adapted plants. The North Slope of
Alaska's Brooks Range also receives less than 250
millimeters (10 in) of precipitation per year and is often
classified as a cold desert.[6] Other regions of the world
have cold deserts, including areas of the Himalayas and
other high altitude areas in other parts of the world. Polar
deserts cover much of the ice free areas of the arctic and
Antarctic.
9.
10. Potential evapotranspiration supplements the measurement of rainfall in
providing a scientific measurement-based definition of a desert. The water
budget of an area can be calculated using the formula P − PE ± S, wherein P is
precipitation, PE is potential evapotranspiration rates and Sis amount of surface
storage of water. Evapotranspiration is the combination of water loss through
atmospheric evaporation and through the life processes of plants. Potential
evapotranspiration, then, is the amount of water that could evaporate in any
given region. As an example,Tucson, Arizona receives about 300 millimeters
(12 in) of rain per year, however about 2500 millimeters (100 in) of water could
evaporate over the course of a year.[citation needed] In other words, about 8 times
more water could evaporate from the region than actually falls. Rates of
evapotranspiration in cold regions such as Alaska are much lower because of
the lack of heat to aid in the evaporation process.
There are different forms of deserts. Cold deserts can be covered
in snow or ice; frozen water unavailable to plant life. These are more commonly
referred to as tundra if a short season of above-freezing temperatures is
experienced, or as an ice cap if the temperature remains below freezing year-
round, rendering the land almost completely lifeless.
11. THE BIBLY
The pretty and delicate bilby once lived across most of the Australian inland deserts. Today its
range is a lot more restricted (due to the usual environmental problems that we humans cause).
Only small, fragmented populations survive in parts of the Tanami, the Gibson and the Great
Sandy deserts.
Like most desert animals the bilby hides during the day and forages at night to avoid heat and
dehydration. Bilbies dig burrows that are one to two metres below ground and moister and up to
ten degrees cooler than the surface.
They are so efficient in conserving water that they don't need to drink. They get enough
moisture from their food: seeds, bulbs, fungi, spiders and insects, which they find by scratching
and digging. Just like the little fellow in the picture above.
12. THE PERENTIE
The Perentie, a two meter
monitor lizard that lives in the
Australian deserts, uses the
same strategy: it shelters in
underground burrows.
Those burrows are huge and
often have many escape
tunnels. Not that the Perentie
would need them. Perenties
are amongst the top
predators in the Australian
deserts.
13. THE THORNY DEVIL
The thorny devil is one of the
most unusual looking animals
of the Australian desert, and its
adaptation to its harsh
environment is ingenious to
say the least.
14. THE BEARDEDDRAGON
Another desert dweller from
the family of Australian
lizards: the bearded dragon.
Bearded dragons are found
mainly in the central desert
regions of Australia.
Let me rephrase that.
Bearded dragons originated
mainly in the central desert
regions of Australia. From
there they conquered the rest
of the planet: they are one of
the most popular pet lizards
in the world.
15. THE RED KANGAROO
The Red Kangaroo, the largest
marsupial in the world, is the most
famous kangaroo species, but it is
only one of many. The "big reds" are
the species that inhabits the driest
parts of Australia, the central deserts.
And their adaptation to their
environment is the one aspect they
are so famous for: the hopping.
Hopping is a fast and very energy-
efficient way to travel. It evolved
because Red Kangaroos need to
cover huge distances to find enough
food in the sparsely vegetated
Australian desert.
16. THE CAMEL
No, the camel is not a native
Australian animal. But when camels
were introduced they did so well that
the camels that escaped or were let
go by their owners multiplied rapidly
and established a big and healthy
population in the Australian Outback
deserts. Today they are everywhere.
Australian deserts contain huge
numbers of wild camels, camel meat
is on the menu of many restaurants
that offer "bush food", we have
camel farms and camel rides are
popular with tourists. We even
export camels back to the countries
they originally came from. Australia
is one of the world's top producers of
camels. No kidding.
Read more about camels in
Australia, and the problems their
exploding numbers are causing for
the fragile Australian desert
environment
17. THE DESERTDINGO
The dingo has lived in Australia for
much longer than any other
introduced animal. Still, it didn't
evolve here. Dingos were
introduced at least 3500 years ago.
The wild dogs had become an
integral part of the Outback
environment, but when white
settlers arrived here, and brought
their sheep, and there was a clash
of interests, the hunter became the
hunted.
Dingo numbers are steadily
declining, so much so that dingos
could become extinct within just a
few decades. And that means we
would be losing our best weapon in
the fight against the most
destructive feral predators and
pests: cats, foxes and rabbits.