Y11GeU4A.3 Deforest Nov25PP.ppt - Ysgol Rhyngrwyd IGCSE Geography

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Y11GeU4A.3 Deforest Nov25PP.ppt - Ysgol Rhyngrwyd IGCSE Geography Powered By Docstoc
					         Aims and objectives
• 1. What is deforestation?
• 2. Why have tropical rainforest been
• 3. What are the impacts of deforestation?

Where the forests are

• Deforestation is cutting down tress – not just
    cutting down forests – as we saw last week
    cutting down trees in the savannah is called that
    too – even though the savannah can hardly be
    called a forest.
•   Many primary forests in temperate countries
    have almost disappeared after centuries of
    logging or land clearance for farming, industry
    and housing. But it is relatively recently that
    large scale deforestation has taken place in the
    tropical forests.
•   Meanwhile there are some temperate areas
    where reforestation is taking place.
•    It speed has raised alarm with the scientists
    and conservationists. What are they concerned
     What are the scientists and
  conservationists concerned about?
• Biodiversity is a major concern. Rainforest
  are one of the most biologically diverse
  regions of the world.
• Over a million species of plants and animals
  are known to live in the forests and
  millions more are not classified.
• The unique environment of the rainforest
  allows for such biodiversity to exist.
• What is most of it cut down for?
 What are causes of deforestation in
       tropical rain forests?
• Logging; Farming; Road building; Mining;
 HEP schemes

    What do the governments think about
• Some of the logging is illegal
• But in many case the governments encourage it.
• Often these are LEDCs with few ways of raising
•   So the temptation to pay off debts and increase
    the standard of living of their people is a hard
    one to pass up
•   What do they gain from allowing deforestation?
      Revenue from timber, drugs (legal ones) and minerals –
       and more recently exports of animal feed (soya) and
       biofuels (palm oil)
      Land to house and feed their increasing population
    So what are the main impacts of
       increased deforestation?
• The impact of deforestation on a large
  scale can be divided in two
• Local Impacts are those that affect the
  immediate area from where the trees are
  being removed.
• Worldwide/International Impacts are
  those aspects which affect everyone

What are the local impacts of increased
• Climate Change
• When an area of rainforest is either cut down or destroyed, there
    are various climate changes that happen as a result. The following is
    a list of the various climate changes with a brief description of why
    they come about.
•   Desiccation of previously moist forest soil
•   What happens is because of the exposure to the sun, the soil gets
    baked and the lack of canopy leaves nothing to prevent the moisture
    from quickly evaporating into the atmosphere. Thus, previously moist
    soil becomes dry and cracked.
•   Dramatic Increase in Temperature Extremes
•   Trees provide shade and the shaded area has a moderated
    temperature. With shade, the temperature may be 37 degrees
    Centigrade during the day and 16 degrees at night. With out the
    shade, temperatures would be much colder during the night and
    around 54 degrees during the day.

What are the local impacts of increased
• Moist Humid Region Changes to Desert
• This is related to the desiccation of previously moist
    forest soil. Primarily because of the lack of moisture and
    the inability to keep moisture, soil that is exposed to the
    sun will dry and turn into desert sand. Even before that
    happens, when the soil becomes dry, dust storms become
    more frequent. At that point, the soil becomes useless.
•   Soil Erosion
•    Deforestation contributes to run-off of rainfall and
    intensified soil erosion. Bare ground, with little added
    humus, increase the rate of sheet and gulley erosion.

What are the local impacts of increased
• Changes in rainfall pattern
• The daily rainfall common in many parts of tropical
    rainfall is called convection rainfall.
•   Heavy rainfall in these areas occurs frequently in the
    afternoon. Why?
•   When it rains, the trees intercept much of the water,
    slowing its rate of descent, allowing much of it to
    percolate into the soil as the ground is shaded and so
    much cooler than the air above. Much of the water that
    has percolated the soil will be taken in by the roots of
    trees and shrubs, which will transpire it into the
    atmosphere in first part of the day when the sky is clear
    and so the temperature rises. This warm moist air rises
    in the atmosphere and eventually cools and condenses
    into clouds in time for the next teatime downpour


                   About 4 o’clock
                   nearly every day
 animated version of this is on http://ysgol-
rhyngrwyd.wikispaces.com/Unit+2+Environmental+conditions   15
So what happens when the trees are cut
• The shrinking forest cover that there are no longer
    trees to intercept, retain and transpire precipitation.
•   The deforested areas become sources of surface water
    runoff, which moves much faster than subsurface flows
    and can cause flash flooding and more localized floods
    than would occur with the forest cover.
•   With decreased evapotranspiration, atmospheric
    moisture is reduced the regular rainfall is reduced.
•   According to one preliminary study, in deforested north
    and northwest China, the average annual precipitation
    decreased by one third between the 1950s and the

What are the international impacts of
     increased deforestation?
• Less Carbon Dioxide and Nitrogen Exchange
• The rainforests are important in the carbon
 dioxide exchange process. They are second only
 to oceans as the most important "sink" for
 atmospheric carbon dioxide. Deforestation may
 account for as much as 10% of current
 greenhouse gas emissions. Greenhouse gases are
 gases in the atmosphere that literally trap heat.
 There is a theory that as more greenhouse
 gasses are released into the atmosphere, more
 heat gets trapped. Thus, there is a global
 warming trend in which the average temperature
 becomes progressively higher.
A summary

    So what are the main impacts of
       increased deforestation?
• Other Effects
• There many rewards such as clean air and
  clean water, perhaps the two most
  important, that forests provide.
• Rainforests also provide many aesthetic,
  recreational and cultural rewards.
• If the rainforests are destroyed, then
  these rewards disappear. This has major
  social repercussions for the entire world
  which will be gone into later.
         Medicines and Rainforests
• Tropical rainforests, which account for only seven
    percent of the world’s total land mass, harbour as much
    as half of all known varieties of plants. Experts say that
    just a four-square-mile area of rainforest may contain as
    many as 1,500 different types of flowering plants and
    750 species of trees, all which have evolved specialized
    survival mechanisms over the millennia that mankind is
    just starting to learn how to appropriate for its own
•   Rainforests are a Rich Source of Medicines
    Scattered pockets of native peoples around the world
    have known about the healing properties of rainforest
    plants for centuries and perhaps longer. But only since
    World War II has the modern world begun to take
    notice, and scores of drug companies today work in
    tandem with conservationists, native groups and various
    governments to find, catalogue and synthesize rainforest
    plants for their medicinal value.
         Medicines and Rainforests
• Rainforest Plants Produce Life-saving Medicines
    Some 120 prescription drugs sold worldwide today are
    derived directly from rainforest plants. And according to
    the U.S. National Cancer Institute, more than two-thirds
    of all medicines found to have cancer-fighting properties
    come from rainforest plants. Examples abound.
    Ingredients obtained and synthesized from a now-
    extinct periwinkle plant found only in Madagascar (until
    deforestation wiped it out) have increased the chances
    of survival for children with leukemia from 20 percent to
    80 percent.
•   Some of the compounds in rainforest plants are also used
    to treat malaria, heart disease, bronchitis, hypertension,
    rheumatism, diabetes, muscle tension, arthritis,
    glaucoma, dysentery and tuberculosis, among other
    health problems. And many commercially available
    anesthetics, enzymes, hormones, laxatives, cough
    mixtures, antibiotics and antiseptics are also derived
    from rainforest plants and herbs.                      21
           Medicines and Rainforests
• The Untapped Potential of Rainforest Medicines
    Despite these success stories, less than one percent of
    the plants in the world’s tropical rainforests have even
    been tested for their medicinal properties.
    Environmentalists and health care advocates alike are
    keen to protect the world’s remaining rainforests as
    storehouses for the medicines of the future.
•   The Challenge of Preserving Valuable Rainforests
    But saving tropical rainforests is no easy task, as
    poverty-stricken native people try to eke out a living off
    the lands and many governments throughout the world’s
    equatorial regions, out of economic desperation as well as
    greed, allow destructive cattle ranching, farming and
    logging. As rainforest turns to farm, ranch and clear-cut,
    some 137 rainforest-dwelling species—plants and animals
    alike—go extinct every single day, according to noted
    Harvard biologist Edward O. Wilson. Conservationists
    worry that as rainforest species disappear, so will many
    possible cures for life-threatening diseases.          22
•   You have met the issues.
•   Our Case study will be the Amazon.
•   Research these questions
•   Qu 1: What are the main causes of deforestation
    in the Amazon? (figures and/or graphs if you
•   Qu 2: What are the main impacts of
    deforestation in the Amazon?
•   Next week, we will look at what can be done
    about all this. How the rainforest can be
    managed, how organisations like REDD and the
    Rainforest Alliance try to cope and individual
    efforts to make the

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