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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.

- [Narrator] Wind whips over a barren wasteland.

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砂漠101|ナショナルジオグラフィック (Deserts 101 | National Geographic)

  • 65 5
    Courtney Shih に公開 2021 年 01 月 14 日
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