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- [Narrator] Wind whips over a barren wasteland.
Vast nothingness as far as the eye can see,
or so it may seem.
Creatures peek out of burrows,
scurry across the sand,
and soar through the sky,
revealing a landscape not as lifeless
as it might first appear.
Deserts are often defined as areas of land
that receive less than 10 inches of rainfall each year.
These regions are low in humidity
and can even be moisture-deficient,
evaporating water faster than it is received.
While most deserts are found in the mid-latitudes,
these diverse ecosystems occur on all seven continents
and make up nearly one-third of Earth's total land mass.
Deserts are sometimes classified into four major types:
subtropical, semiarid, coastal, and polar.
Subtropical deserts are found along the equator,
and the Tropic of Cancer, and the Tropic of Capricorn.
They are the hottest deserts on Earth,
with daytime temperatures
that can reach up to 120 degrees Fahrenheit.
Semiarid deserts are located in Asia,
Europe, and North America.
These cold-winter deserts often form
when tall mountain ranges block moisture
through a process called the rain-shadow effect.
Coastal deserts form alongside the tropical western edges
of certain continents.
Despite their proximity to water,
coastal deserts remain dry.
Polar deserts are found in the Arctic and Antarctic.
The other end of the extreme,
winter temperatures in the Antarctic Desert
average around minus 50 degrees Fahrenheit.
While deserts experience extreme temperatures
and receive very little precipitation,
they are still important habitats for plants and animals.
Desert animals, such as the coyote,
have evolved to withstand harsh desert conditions
by burrowing into the cool ground
and emerging at night, when desert temperatures drop.
Many desert plants, including the saguaro cactus,
have established long and shallow root systems
to better absorb what minimal moisture might be present
in the ground.
Highly specialized to survive in such a harsh environment,
desert wildlife is particularly vulnerable
to ecological changes.
Existing deserts have become less habitable
because of rising temperatures
that dry up scarce water resources
and increase the risk of wildfires.
Additionally, new desert areas are beginning to form
through desertification.
This phenomenon occurs when factors such as deforestation,
climate change, and resource mismanagement
degrade the biological productivity of a region,
thereby creating a desert.
For instance, in Central Asia,
poor irrigation practices and excessive water usage
dried up the Aral Sea
and formed the youngest desert on the planet.
But by practicing responsible agriculture,
better management of limited water resources,
and limiting further development,
it may be possible to curb desertification
while protecting our surprisingly rich desert ecosystems.


Deserts 101 | National Geographic

31 分類 收藏
Courtney Shih 發佈於 2020 年 1 月 21 日
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