unit10 deforestation.ppt

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    DEFORESTATIONDEFORESTATIONDesign by Joe Naumann

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    Unit XI. Deforestation and the role of forests

    in the climate system.

    A. History of forests

    Earth 4.6 byr

    Life >3 byr

    Multicellular Life 600 myr

    Plants on land 400 myr (green algae)

    Ferns, etc. 200 - 70 myrFlowering plants 100 myr

    (Angiosperrms)

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    Unit XI. Deforestation and the role of forests in

    the climate system.

    A. History of forests

    • First land plants short…..

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    Unit XI. Deforestation and the role of forests

    in the climate system.

    B. Forest types

    • Boreal Forests (conifers)

    • Temperate Forests

    (mixed deciduous hardwoods)

    • Tropical Rainforests

    (conifers and hardwoods)

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    NPP: Net Primary Productivity

    What is the net annual production of organicmatter by a particular ecosystem,usually

    measured in the amount of Carbon fixed as

    organic matter.Net means the total fixed minus the total

    respired.

    gC/km2 /yr is the (net) grams of carbon fixed

    over each square kilometer in an average year.

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    Characteristics of Earth’s Forests

    Forest

    Type

    Where? Area

    (km2

    )Rainfall Soil

    NPP

    gC/km2 /yr

    Biodiv-

    ersity

    Boreal

    Temperate

    Tropical

    Rainforest

    High N

    Latitudes(50-60 °N)

    Mid-

    Latitude(30° - 50°)

    Low

    Latitude

    (0 - 30°)

    12 M

    12 M

    17 M

     Low

    20-50

    cm/yr

    Moderate

    50 to 100

     cm/yr

     High

    2 to 10

      m/yr

    Immature, but

    abundant

    minerals yet

    to be released

    Rich, fertile,

    abundant

    nutrient

    reservesPoor, highly

    leached. Most

    nutrients

    recycles

    300 M

    500 M

    1000 M

    Low

    High

    Moderate

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    Unit XI. Deforestation and the role of forests in

    the climate system.

    B. Forest types

    • Boreal Forests: slow growing, cold, 1/2

    year low light, shallow, immature, but

    mineral-rich soils. Low plant and animal

    diversity.

    Capable of sustained harvest, but low yield

    (slow growth)

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    Unit XI. Deforestation and the role of forests in

    the climate system.

    B. Forest types

    • Temperature Forests: Mixed deciduous

    hardwoods and evergreens, fertile soils.

    Resistent to disturbance: if cleared, rapid

    recolonization.

    Sustained yield OK in most regions.

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    Unit XI. Deforestation and the role of forests in

    the climate system.

    B. Forest types

    • Tropical Rainforest: Closed canopy, high

    rainfall. Most in Brazil (Amazonia),

    central West Africa (Congo, Zaire),

    Indonesia and Madigascar. Also Central

    America, Angola, Peru, Bolivia, India and

    scattered outliers.

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    Percentage

    area coveredby different

    ecosystems

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    NPP (gC/m2 /yr)

    for differentecosystems

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    Percentage net

    NPP

    (gC/m2 /yr) fordifferent

    ecosystems

    70%

    3%

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    Unit XI. Deforestation and the role of forests

    in the climate system.

    B. Forest types

    • Tropical Rainforest are the lungs of the

    world. They inhale CO2

     and exhale O2

     

    through the process of photosynthesis.

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    Unit XI. Deforestation and the role of forests

    in the climate system.

    B. Forest types

    • Tropical Rainforest: The risky bit…..

    Soils: Ancient, little rock, highly leached

    (high rainfall), and few sources of new

    nutrients. Almost all nutrients are

    recycled.

    Incapable of sustained high harvest.

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    Unit XI. Deforestation and the role of forests

    in the climate system.C. Deforestation: why we should be

    concerned.

    • Loss of biodiversity

    • Global warming (burning releases CO2)

    • Climate impacts

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    Unit XI. Deforestation and the role of forests

    in the climate system.

    D. The role of forests in the climate system.

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    How a geologist

    views a tree.…Key

    variables:

    Leaf area index

    Rooting depth

    Water-holding

    capacity of the soil.

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    D. The role of forests in the climate system.

    Amazonia: Estimated that 50% of the rainfall

    over the Amazon Basin is recycled water.

    During a rainfall event, leaves intercept rainwater,

    and organic-rich soil absorbs rainfall. Leaf

    evaporation and transpiration returns water vaporto the atmosphere.

    Two effects:

    • landward migration of rainfall• water vapor fuels more storms

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    D. The role of forests in the climate system.

    Amazonian Paradox:

    Amazon rainforest requires heavy rainfall to

    exist, but half the rainfall is itself depedent on

    the rainforest being present.

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    D. The role of forests in the climate system.

    Examples:

    Two adjacent catchments…. One clear cut,

    the other left forested. Stream runoff in the

    deforested catchment was 4 to 10 times theforested catchment. Rainfall similar in the

    two basins, so difference is decreased

    evapotranspiration.

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    Forested Deforested

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    D. The role of forests in the climate system.

    Examples:

    Ivory Coast: Replacement of rainforest by cropland

    over last 5 deacdes,; runoff increased 8-fold.

    Areas formerly suitable for cocoa now abandoneddue to lower rainfall, less humidity and more

    extreme summer temperatures.

    Similar example in India where rice production fell

    after rainforest removed.

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    D. The role of forests in the climate system.

    Examples: Ivory Coast, India

    Proving cause and effect is difficult, but first

    principles provides a reasonable mechanism

    to explain these observations.