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Desertification - PowerPoint by Kj24Q1

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									Desertification
   Desertification is the process by which a
    productive dryland area is degraded to the point
    that it becomes unproductive desert land.

   In most cases desertification is caused by human
    activities. The most common practices that lead
    to it are:

   Over-cultivation
   Overgrazing
   Deforestation
   Inappropriate irrigation techniques

   Dryland areas have very delicately balanced
    ecosystems that have evolved over thousands of
    years so that the animals and plants in those
    areas have adapted to seasonal water shortages.
   The desertification process usually starts when the
    cover of native plants is removed from dryland
    areas.

   People may do this to clear the area for
    agriculture, or they may have cut down all the
    trees and shrubs to use for firewood or building
    materials.

   With the plant life gone, the soil loses its moisture
    more quickly and becomes more vulnerable to
    erosion.
   As the soil dries out, it presses together, or
    compacts.

   When this happens the soil becomes
    impervious, that is, it loses the ability to absorb
    what little rain it does receive.

   New vegetation cannot establish itself in such an
    area, and without the necessary organic material
    and water, the soil cannot recover its fertility.
   On irrigated land, the soil may become sterile or
    lifeless because the repeated irrigation causes a
    buildup of salts to such a level that plants can no
    longer survive.

   The consequences of desertification are very
    serious.

   As more and more land changes to infertile desert,
    the people who live there are forced to seek new
    places to grow their food. In the meantime, they
    are subject to starvation and malnutrition.

   Deserts can contribute to weather changes by
    raising temperatures and lowering humidity levels.

   Biodiversity suffers, as living organisms face peril,
    with food and shelter disappearing.
Read pages 120-123
      Once you finish reading, answer the
            assigned questions below.

a)        What are the sequence of events that
            typically lead to desertification?

     b)    What are the consequences of this
               process?Briefly explain.

 Once you have answered the above two
  questions, turn to pages 126 and 127 in
   your text and answer questions 11, 12
    and 13. Write in complete sentences.

								
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